android activity启动流程，Android常用组件Activity启动详细流程
android activity启动流程，Android常用组件Activity启动详细流程ActvityiManagerService.startActivityAsUser() ActivityStackSupervisor.startActivityMayWait() ActivityStackSupervisor.startActivityLocked() ActivityStackSupervisor.startActivityUncheckedLocked() ActivityStackSupervisor.startActivityLocked() ActivityStackSupervisor.resumeTopActivitiesLocked() ActivityStackSupervisor.resumeTopActivityInnerLocked()<pre spellcheck="false" class="md-fences
一、Activity请求启动
我们以startActivity这种来分析
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n6" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">Intent intent=new Intent(MainActivity.this TargetActivity.class);
startActivity(intent);</pre>
经过startActivity-->startActivityForResult-->execStartActivity 最终会调用Instrumentation的execStartActivity方法
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n8" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">public ActivityResult execStartActivity(
Context who IBinder contextThread IBinder token Activity target
Intent intent int requestCode Bundle options) {
IApplicationThread whoThread = (IApplicationThread) contextThread;
Uri referrer = target != null ? target.onProvideReferrer() : null;
if (referrer != null) {
intent.putExtra(Intent.EXTRA_REFERRER referrer);
}
.....
try {
intent.migrateExtraStreamToClipData();
intent.prepareToLeaveProcess(who);
//获取AMS的代理，启动Activity
int result = ActivityManagerNative.getDefault()
.startActivity(whoThread who.getBasePackageName() intent
intent.resolveTypeIfNeeded(who.getContentResolver())
token target != null ? target.mEmbeddedID : null
requestCode 0 null options);
//检查Activity是否启动成功，若失败给出是什么原因
checkStartActivityResult(result intent);
} catch (RemoteException e) {
throw new RuntimeException("Failure from system" e);
}
return null;
}
}</pre>
这些参数的意思是：
- this，为启动Activity的对象；
- contextThread，为Binder对象，是主进程的context对象；
- token，也是一个Binder对象，指向了服务端一个ActivityRecord对象；
- target，为启动的Activity；
- intent，启动的Intent对象；
- requestCode，请求码；
- options，参数；
先看checkStartActivityResult方法的实现
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n28" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public static void checkStartActivityResult(int res Object intent) {
if (res >= ActivityManager.START_SUCCESS) {
return;
}
switch (res) {
case ActivityManager.START_INTENT_NOT_RESOLVED:
case ActivityManager.START_CLASS_NOT_FOUND:
if (intent instanceof Intent && ((Intent)intent).getComponent() != null)
throw new ActivityNotFoundException(
"Unable to find explicit activity class "
((Intent)intent).getComponent().toShortString()
"; have you declared this activity in your AndroidManifest.xml?");
throw new ActivityNotFoundException(
"No Activity found to handle " intent);
case ActivityManager.START_PERMISSION_DENIED:
throw new SecurityException("Not allowed to start activity "
intent);
case ActivityManager.START_FORWARD_AND_REQUEST_CONFLICT:
throw new AndroidRuntimeException(
"FORWARD_RESULT_FLAG used while also requesting a result");
case ActivityManager.START_NOT_ACTIVITY:
throw new IllegalArgumentException(
"PendingIntent is not an activity");
case ActivityManager.START_NOT_VOICE_COMPATIBLE:
throw new SecurityException(
"Starting under voice control not allowed for: " intent);
case ActivityManager.START_VOICE_NOT_ACTIVE_SESSION:
throw new IllegalStateException(
"Session calling startVoiceActivity does not match active session");
case ActivityManager.START_VOICE_HIDDEN_SESSION:
throw new IllegalStateException(
"Cannot start voice activity on a hidden session");
case ActivityManager.START_CANCELED:
throw new AndroidRuntimeException("Activity could not be started for "
intent);
default:
throw new AndroidRuntimeException("Unknown error code "
res " when starting " intent);
}
}</pre>
常见的ActivityNotFoundException，SecurityException等错日志就在这里报出来的；
OK，现在回到execStartActivity，内部调用了ActivityManagerNative.getDefault().startActivity，关于ActivityManagerNative已经说了很多了，相当于AMS服务端存根或者代理，其客户端是ActivityManagerNative的内部类ActivityManagerProxy，这里getDefault获取的就是ActivityManagerProxy对象，通过ActivityManagerProxy对象来使用AMS内部的一些服务，包括单不限于启动Activity
所以通过ActivityManagerProxy对象调用startActivity方法的实质是调用BinderProxy.transact向Binder驱动发送START_ACTIVITY_TRACSACTION命令，binder驱动将处理逻辑从Launcher所在的进程切换到AMS所在的SystemServer进程。OK，我们直接看ActivityManagerService的startActivity方法，不明白，建议看一下Binder的通信原理。
二、AMS处理Activity的启动请求2.1、AMS处理Activity的启动请求<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n33" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> @Override
public final int startActivity(IApplicationThread caller String callingPackage
Intent intent String resolvedType IBinder resultTo String resultWho int requestCode
int startFlags ProfilerInfo profilerInfo Bundle bOptions) {
return startActivityAsUser(caller callingPackage intent resolvedType resultTo
resultWho requestCode startFlags profilerInfo bOptions
UserHandle.getCallingUserId());
}</pre>
保持篇幅，以下步骤省略
ActvityiManagerService.startActivityAsUser() ActivityStackSupervisor.startActivityMayWait() ActivityStackSupervisor.startActivityLocked() ActivityStackSupervisor.startActivityUncheckedLocked() ActivityStackSupervisor.startActivityLocked() ActivityStackSupervisor.resumeTopActivitiesLocked() ActivityStackSupervisor.resumeTopActivityInnerLocked()
在resumeTopActivityInnerLocked的内部有如下代码
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n38" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> if (mResumedActivity != null) {
if (DEBUG_STATES) Slog.d(TAG_STATES
"resumeTopActivityLocked: Pausing " mResumedActivity);
pausing |= startPausingLocked(userLeaving false true dontWaitForPause);
}
</pre>
这表明在启动一个Activity的时候，前面一个Activity要执行onPause方法，onPause方法是怎么调用的呢？
2.2、AMS调用栈顶Activity的onPause<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n41" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> final boolean startPausingLocked(boolean userLeaving boolean uiSleeping boolean resuming
boolean dontWait) {
......
if (mService.mHasRecents && (next == null || next.noDisplay || next.task != prev.task || uiSleeping)) {
prev.updateThumbnailLocked(screenshotActivities(prev) null);
}
stopFullyDrawnTraceIfNeeded();
mService.updateCpuStats();
if (prev.app != null && prev.app.thread != null) {
if (DEBUG_PAUSE) Slog.v(TAG_PAUSE "Enqueueing pending pause: " prev);
try {
//调用ApplicationThread的schedulePauseActivity
prev.app.thread.schedulePauseActivity(prev.appToken prev.finishing
userLeaving prev.configChangeFlags dontWait);
} catch (Exception e) {
......
}
}
......
}</pre>
这里先留一个问题， 我知道prev.app.thread是ApplicationThreadProxy对象，实际是调用了ApplicationThread的schedulePauseActivity方法，但是 AMS是怎么获取到prev.app.thread的呢？
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n43" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public final void schedulePauseActivity(IBinder token boolean finished
boolean userLeaving int configChanges boolean dontReport) {
sendMessage(
finished ? H.PAUSE_ACTIVITY_FINISHING : H.PAUSE_ACTIVITY
token
(userLeaving ? 1 : 0) | (dontReport ? 2 : 0)
configChanges);
}
</pre>
关键就是最后调用了sendMessage(H.BIND_APPLICATION data) 发送了消息； 关于H这个类，其实是个Hander，我觉得它的作用就像是一个交通枢纽；H接收到这个Message之后，调用
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n45" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> handlePauseActivity((IBinder)msg.obj false (msg.arg1&1) != 0 msg.arg2 (msg.arg1&2) != 0);</pre>
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n46" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> private void handlePauseActivity(IBinder token boolean finished
boolean userLeaving int configChanges boolean dontReport) {
ActivityClientRecord r = mActivities.get(token);
.......
r.activity.mConfigChangeFlags |= configChanges;
performPauseActivity(token finished r.isPreHoneycomb());
.......
// Tell the activity manager we have paused.
if (!dontReport) {
try {
ActivityManagerNative.getDefault().activityPaused(token);
} catch (RemoteException ex) {
}
}
mSomeActivitiesChanged = true;
}
}</pre>
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n47" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> final Bundle performPauseActivity(ActivityClientRecord r boolean finished
boolean saveState) {
if (r.paused) {
.......
try {
.......
//调用Instrumentation的callActivityOnPause方法
mInstrumentation.callActivityOnPause(r.activity);
EventLog.writeEvent(LOG_AM_ON_PAUSE_CALLED UserHandle.myUserId()
r.activity.getComponentName().getClassName());
if (!r.activity.mCalled) {
throw new SuperNotCalledException(
"Activity " r.intent.getComponent().toShortString()
" did not call through to super.onPause()");
}
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
.......
}
}
r.paused = true;
.......
return !r.activity.mFinished && saveState ? r.state : null;
}</pre>
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n48" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public void callActivityOnPause(Activity activity) {
activity.performPause();
}
</pre>
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n49" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> final void performPause() {
mDoReportFullyDrawn = false;
mFragments.dispatchPause();
mCalled = false;
//onPause执行
onPause();
mResumed = false;
if (!mCalled && getApplicationInfo().targetSdkVersion
>= android.os.Build.VERSION_CODES.GINGERBREAD) {
throw new SuperNotCalledException(
"Activity " mComponent.toShortString()
" did not call through to super.onPause()");
}
mResumed = false;
}</pre>
分析到这里 onPause()终于执行了； 回到 handlePauseActivity方法中，在这个方法最后调用了ActivityManagerNative.getDefault().activityPaused(token)
2.3、ActivityManagerService的activityPaused方法执行<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n52" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> @Override
public final void activityPaused(IBinder token) {
final long origId = Binder.clearCallingIdentity();
synchronized(this) {
ActivityStack stack = ActivityRecord.getStackLocked(token);
if (stack != null) {
stack.activityPausedLocked(token false);
}
}
Binder.restoreCallingIdentity(origId);
}</pre>
经过一些方法，最终会调用startSpecificActivityLocked
ActivityStack.activityPausedLocked() ActivityStack.completePauseLocked() ActivityStackSupervisor.resumeTopActivitiesLocked() ActivityStack.resumeTopActivityLocked() ActivityStack.resumeTopActivityInnerLocked () ActivityStack.startSpecificActivityLocked ()
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n56" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> void startSpecificActivityLocked(ActivityRecord r
boolean andResume boolean checkConfig) {
// Is this activity's application already running?
ProcessRecord app = mService.getProcessRecordLocked(r.processName
r.info.applicationInfo.uid true);
r.task.stack.setLaunchTime(r);
if (app != null && app.thread != null) {
try {
if ((r.info.flags&ActivityInfo.FLAG_MULTIPROCESS) == 0
|| !"android".equals(r.info.packageName)) {
// Don't add this if it is a platform component that is marked
// to run in multiple processes because this is actually
// part of the framework so doesn't make sense to track as a
// separate apk in the process.
app.addPackage(r.info.packageName r.info.applicationInfo.versionCode
mService.mProcessStats);
}
realStartActivityLocked(r app andResume checkConfig);
return;
} catch (RemoteException e) {
Slog.w(TAG "Exception when starting activity "
r.intent.getComponent().flattenToShortString() e);
}
// If a dead object exception was thrown -- fall through to
// restart the application.
}
mService.startProcessLocked(r.processName r.info.applicationInfo true 0
"activity" r.intent.getComponent() false false true);
}
</pre>
如果需要启动的Activity所需要的应用进程是否已经启动，如果没有则执行realStartActivityLocked去启动Activity 否则去启动启动应用进程，相当于一个预启动的过程
2.4、应用进程创建startProcessLocked是怎么执行的？ SystemServer进程中Ams通过Socket与Zygote进程进行通信的，Zygote接收到AMS发起的创建进程的请求，会fork出一个子进程，并且反射调用这个进程中ActivityThread的main方法 在应用进程启动之后，ActivityThread的main方法就开始执行了
三、ActivityThread的main方法执行在ActivityThread的main方法里调用thread.attach(false)
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n62" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public static void main(String[] args) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER "ActivityThreadMain");
SamplingProfilerIntegration.start();
......
Process.setArgV0("<pre-initialized>");
Looper.prepareMainLooper();
ActivityThread thread = new ActivityThread();
thread.attach(false);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG "ActivityThread"));
}
// End of event ActivityThreadMain.
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
}</pre>
对于上面main方法，相信很多人都看多很多遍了，接下来重点分析 thread.attach(false)这行代码
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n64" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {
.......
//获取ActivityManagerService在客户端的代理
IActivityManager mgr = ActivityManagerNative.getDefault();
try {
//实质是调用ActivityManagerService的attachApplication方法 目的是让ActivityManagerService通过ApplicationThread代理对象控制应用进程
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
}
}
.......
}</pre>
在调用 mgr.attachApplication()的时候，将mAppThread对象传进去了
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n66" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> final ApplicationThread mAppThread = new ApplicationThread();</pre>
ApplicationThread继承了ApplicationThreadNative， 看一下ApplicationThreadNative里面的方法
内部调用了ActivityManagerNative.getDefault() .attachApplication，关于ActivityManagerNative已经说了很多了，相当于AMS服务端存根或者代理，其客户端是ActivityManagerNative的内部类ActivityManagerProxy，这里getDefault获取的就是ActivityManagerProxy对象，通过ActivityManagerProxy对象来使用AMS内部的一些服务，包括单不限于启动Activity
所以通过ActivityManagerProxy对象调用attachApplication方法的实质是调用BinderProxy.transact向Binder驱动发送ATTACH_APPLICATION_TRANSACTION命令，binder驱动将处理逻辑从APP应用进程所在的进程切换到AMS所在的SystemServer进程
OK，我们直接看ActivityManagerService的attachApplication方法：
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n69" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> @Override
public final void attachApplication(IApplicationThread thread) {
synchronized (this) {
int callingPid = Binder.getCallingPid();
final long origId = Binder.clearCallingIdentity();
attachApplicationLocked(thread callingPid);
Binder.restoreCallingIdentity(origId);
}
}</pre>
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n70" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">private final boolean attachApplicationLocked(IApplicationThread thread
int pid) {
ProcessRecord app;
if (pid != MY_PID && pid >= 0) {
synchronized (mPidsSelfLocked) {
//通过进程ID，获取进程的记录信息
app = mPidsSelfLocked.get(pid);
}
} else {
app = null;
}
if (app == null) {
Slog.w(TAG "No pending application record for pid " pid
" (IApplicationThread " thread "); dropping process");
EventLog.writeEvent(EventLogTags.AM_DROP_PROCESS pid);
if (pid > 0 && pid != MY_PID) {
//如果没有获取到，需要杀死该进程，MY_PID是系统进程
Process.killProcessQuiet(pid);
} else {
......
return false;
}
......
//获取进程名称
final String processName = app.processName;
try {
AppDeathRecipient adr = new AppDeathRecipient(
app pid thread);
thread.asBinder().linkToDeath(adr 0);
app.deathRecipient = adr;
} catch (RemoteException e) {
app.resetPackageList(mProcessStats);
startProcessLocked(app "link fail" processName);
return false;
}
EventLog.writeEvent(EventLogTags.AM_PROC_BOUND app.userId app.pid app.processName);
//设置进程的OOM，adj等值
//还记得上面留下的那个问题吗，AMS是怎么获取到prev.app.thread的呢？就在这，prev.app是ProcessRecord对象，makeActive内部将thread对象赋值给prev.app.thread。可以自己查阅，这样AMS是可以查询进程记录的，进程记录中就有一个app.thread，若AMS要跟Activity通信直接获取prev.app.thread就可以了。
app.makeActive(thread mProcessStats);
app.curAdj = app.setAdj = -100;
app.curSchedGroup = app.setSchedGroup = Process.THREAD_GROUP_DEFAULT;
app.forcingToForeground = null;
updateProcessForegroundLocked(app false false);
app.hasShownUi = false;
app.debugging = false;
app.cached = false;
app.killedByAm = false;
//将attach之前的超时Meessage移除掉
mHandler.removeMessages(PROC_START_TIMEOUT_MSG app);
boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);
List<ProviderInfo> providers = normalMode ? generateApplicationProvidersLocked(app) : null;
......
try {
......
thread.bindApplication(processName appInfo providers app.instrumentationClass
profilerInfo app.instrumentationArguments app.instrumentationWatcher
app.instrumentationUiAutomationConnection testMode enableOpenGlTrace
isRestrictedBackupMode || !normalMode app.persistent
new Configuration(mConfiguration) app.compat
getCommonServicesLocked(app.isolated)
mCoreSettingsObserver.getCoreSettingsLocked());
updateLruProcessLocked(app false null);
app.lastRequestedGc = app.lastLowMemory = SystemClock.uptimeMillis();
} catch (Exception e) {
// todo: Yikes! What should we do? For now we will try to
// start another process but that could easily get us in
// an infinite loop of restarting processes...
Slog.wtf(TAG "Exception thrown during bind of " app e);
app.resetPackageList(mProcessStats);
app.unlinkDeathRecipient();
startProcessLocked(app "bind fail" processName);
return false;
}
......
// See if the top visible activity is waiting to run in this process...
if (normalMode) {
try {
if (mStackSupervisor.attachApplicationLocked(app)) {
didSomething = true;
}
} catch (Exception e) {
Slog.wtf(TAG "Exception thrown launching activities in " app e);
badApp = true;
}
}
// 执行等待进程而暂时挂起的Service
if (!badApp) {
try {
didSomething |= mServices.attachApplicationLocked(app processName);
} catch (Exception e) {
Slog.wtf(TAG "Exception thrown starting services in " app e);
badApp = true;
}
}
// 执行等待进程而暂时挂起的广播
if (!badApp && isPendingBroadcastProcessLocked(pid)) {
try {
didSomething |= sendPendingBroadcastsLocked(app);
} catch (Exception e) {
// If the app died trying to launch the receiver we declare it 'bad'
Slog.wtf(TAG "Exception thrown dispatching broadcasts in " app e);
badApp = true;
}
}
......
if (!didSomething) {
//调整进程优先级adj的值
updateOomAdjLocked();
}
return true;
}</pre>
发现AMS用IApplicationThread对象thread调用了bindApplication，thread实际上就是ApplicationThreadProxy对象； AMS通过ApplicationThreadProxy对象与ActivityThread通信。所以去ApplicationThread中看bindApplication的真正实现
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n72" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public final void bindApplication(String processName ApplicationInfo appInfo
List<ProviderInfo> providers ComponentName instrumentationName
ProfilerInfo profilerInfo Bundle instrumentationArgs
IInstrumentationWatcher instrumentationWatcher
IUiAutomationConnection instrumentationUiConnection int debugMode
boolean enableOpenGlTrace boolean isRestrictedBackupMode boolean persistent
Configuration config CompatibilityInfo compatInfo Map<String IBinder> services
Bundle coreSettings) {
if (services != null) {
// Setup the service cache in the ServiceManager
ServiceManager.initServiceCache(services);
}
setCoreSettings(coreSettings);
......
AppBindData data = new AppBindData();
data.processName = processName;
data.appInfo = appInfo;
data.providers = providers;
data.instrumentationName = instrumentationName;
data.instrumentationArgs = instrumentationArgs;
data.instrumentationWatcher = instrumentationWatcher;
data.instrumentationUiAutomationConnection = instrumentationUiConnection;
data.debugMode = debugMode;
data.enableOpenGlTrace = enableOpenGlTrace;
data.restrictedBackupMode = isRestrictedBackupMode;
data.persistent = persistent;
data.config = config;
data.compatInfo = compatInfo;
data.initProfilerInfo = profilerInfo;
sendMessage(H.BIND_APPLICATION data);
}</pre>
这里又是用H发送了一个消息，是不是很像一个交通枢纽
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n74" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER "bindApplication");
AppBindData data = (AppBindData)msg.obj;
handleBindApplication(data);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
</pre>
handleBindApplication内部就不分析了，Applcation对象的onCreate方法调用就是在这里面，它内部创建了Applcation对象
四、Activity周期如何执行4.1、Activity的onCreate是怎么回调的回到第二小节的startSpecificActivityLocked方法
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n79" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> void startSpecificActivityLocked(ActivityRecord r
boolean andResume boolean checkConfig) {
// Is this activity's application already running?
ProcessRecord app = mService.getProcessRecordLocked(r.processName
r.info.applicationInfo.uid true);
r.task.stack.setLaunchTime(r);
if (app != null && app.thread != null) {
try {
if ((r.info.flags&ActivityInfo.FLAG_MULTIPROCESS) == 0
|| !"android".equals(r.info.packageName)) {
app.addPackage(r.info.packageName r.info.applicationInfo.versionCode
mService.mProcessStats);
}
realStartActivityLocked(r app andResume checkConfig);
return;
} catch (RemoteException e) {
Slog.w(TAG "Exception when starting activity "
r.intent.getComponent().flattenToShortString() e);
}
// If a dead object exception was thrown -- fall through to
// restart the application.
}
mService.startProcessLocked(r.processName r.info.applicationInfo true 0
"activity" r.intent.getComponent() false false true);
}</pre>
在预启动之后，一般我们的应用进程就被孵化来了，直接执行realStartActivityLocked去启动Activity
在realStartActivityLocked内部调用了如下代码，现在你应该知道 app.thread是什么了
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n82" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> app.thread.scheduleLaunchActivity(new Intent(r.intent) r.appToken
System.identityHashCode(r) r.info new Configuration(mService.mConfiguration)
new Configuration(stack.mOverrideConfig) r.compat r.launchedFromPackage
task.voiceInteractor app.repProcState r.icicle r.persistentState results
newIntents !andResume mService.isNextTransitionForward() profilerInfo);</pre>
直接到scheduleLaunchActivity真正实现，它的真正实现是在Applciation中的
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n84" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public final void scheduleLaunchActivity(Intent intent IBinder token int ident
ActivityInfo info Configuration curConfig Configuration overrideConfig
CompatibilityInfo compatInfo String referrer IVoiceInteractor voiceInteractor
int procState Bundle state PersistableBundle persistentState
List<ResultInfo> pendingResults List<ReferrerIntent> pendingNewIntents
boolean notResumed boolean isForward ProfilerInfo profilerInfo) {
updateProcessState(procState false);
ActivityClientRecord r = new ActivityClientRecord();
r.token = token;
r.ident = ident;
r.intent = intent;
r.referrer = referrer;
r.voiceInteractor = voiceInteractor;
r.activityInfo = info;
r.compatInfo = compatInfo;
r.state = state;
r.persistentState = persistentState;
r.pendingResults = pendingResults;
r.pendingIntents = pendingNewIntents;
r.startsNotResumed = notResumed;
r.isForward = isForward;
r.profilerInfo = profilerInfo;
r.overrideConfig = overrideConfig;
updatePendingConfiguration(curConfig);
sendMessage(H.LAUNCH_ACTIVITY r);
}
</pre>
经过一堆的变量赋值之后，又通过H发送了一个消息LAUNCH_ACTIVITY，H在收到这个消息之后，执行下面
<pre spellcheck="false" class="md-fences mock-cm md-end-block" lang="java" cid="n86" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: pre-wrap; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER "activityStart");
final ActivityClientRecord r = (ActivityClientRecord) msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo r.compatInfo);
handleLaunchActivity(r null);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);</pre>
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n87" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> private void handleLaunchActivity(ActivityClientRecord r Intent customIntent) {
// If we are getting ready to gc after going to the background well
// we are back active so skip it.
unscheduleGcIdler();
mSomeActivitiesChanged = true;
if (r.profilerInfo != null) {
mProfiler.setProfiler(r.profilerInfo);
mProfiler.startProfiling();
}
// Make sure we are running with the most recent config.
handleConfigurationChanged(null null);
if (localLOGV) Slog.v(
TAG "Handling launch of " r);
// Initialize before creating the activity
WindowManagerGlobal.initialize();
//一个 perform开头的方法，启动Activity
Activity a = performLaunchActivity(r customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
Bundle oldState = r.state;
//Launch
handleResumeActivity(r.token false r.isForward
!r.activity.mFinished && !r.startsNotResumed);
if (!r.activity.mFinished && r.startsNotResumed) {
try {
r.activity.mCalled = false;
mInstrumentation.callActivityOnPause(r.activity);
if (r.isPreHoneycomb()) {
r.state = oldState;
}
if (!r.activity.mCalled) {
throw new SuperNotCalledException(
"Activity " r.intent.getComponent().toShortString()
" did not call through to super.onPause()");
}
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
.....
}
r.paused = true;
}
.....
}
}</pre>
这个方法会将Activity创建出来
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n89" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> private Activity performLaunchActivity(ActivityClientRecord r Intent customIntent) {
ActivityInfo aInfo = r.activityInfo;
r.activityInfo.targetActivity);
......
Activity activity = null;
try {
java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
activity = mInstrumentation.newActivity(
cl component.getClassName() r.intent);
.......
} catch (Exception e) {
.......
}
Application app = r.packageInfo.makeApplication(false mInstrumentation);
if (localLOGV) Slog.v(TAG "Performing launch of " r);
if (activity != null) {
activity.attach(appContext this getInstrumentation() r.token
r.ident app r.intent r.activityInfo title r.parent
r.embeddedID r.lastNonConfigurationInstances config
r.referrer r.voiceInteractor);
.......
//Activity的create方法执行
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity r.state r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity r.state);
}
.......
r.activity = activity;
r.stopped = true;
if (!r.activity.mFinished) {
//Activity的start方法执行
activity.performStart();
r.stopped = false;
}
mActivities.put(r.token r);
return activity;
}</pre>
反射创建Activity，为啥要用反射呢，此处搞不清楚
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n91" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public Activity newActivity(ClassLoader cl String className
Intent intent)
throws InstantiationException IllegalAccessException
ClassNotFoundException {
return (Activity)cl.loadClass(className).newInstance();
}
</pre>
解析来mInstrumentation调用callActivityOnCreate方法
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n93" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public void callActivityOnCreate(Activity activity Bundle icicle
PersistableBundle persistentState) {
prePerformCreate(activity);
activity.performCreate(icicle persistentState);
postPerformCreate(activity);
}</pre>
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n94" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> final void performCreate(Bundle icicle) {
onCreate(icicle);
mActivityTransitionState.readState(icicle);
performCreateCommon();
}</pre>
onCreate方法在此处被调用了。
4.2、Activity的onStart是怎么回调的在performLaunchActivity中调用了callActivityOnCreate之后，又会调用 activity.performStart()
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n98" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> final void performStart() {
mActivityTransitionState.setEnterActivityOptions(this getActivityOptions());
mFragments.noteStateNotSaved();
mCalled = false;
mFragments.execPendingActions();
mInstrumentation.callActivityOnStart(this);
if (!mCalled) {
throw new SuperNotCalledException(
"Activity " mComponent.toShortString()
" did not call through to super.onStart()");
}
mFragments.dispatchStart();
mFragments.reportLoaderStart();
mActivityTransitionState.enterReady(this);
}</pre>
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n99" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public void callActivityOnStart(Activity activity) {
activity.onStart();
}</pre>
到此处start方法又被调用了。
4.3、Activity的onResume是怎么回调的handleLaunchActivity方法中，在调用performLaunchActivity之后，调用了handleResumeActivity方法。
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n103" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">ActivityThread.handleResumeActivity()
ActivityThread.handleResumeActivity()
Activity.performResume()
Instrumentation.callActivityOnResume();</pre>
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java" cid="n104" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248 248 248); position: relative !important; border: 1px solid rgb(231 234 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51 51 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"> public void callActivityOnResume(Activity activity) {
activity.mResumed = true;
activity.onResume();
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i<N; i ) {
final ActivityMonitor am = mActivityMonitors.get(i);
am.match(activity activity activity.getIntent());
}
}
}
}</pre>
到此Activity的onResume方法被调用，onPause方法已经讲解过，关于onStop，onDestory一样的套路分析。
五、总结关于Activity的启动过程分析，三篇文章都分析完了
- 启动一个Activity的方式有多种，都是通过向Ams发送startActivity请求
- Ams在启动Activity的时候，会判断目标进程有没有被创建，没有创建的话，向zygote进程发送创建进程的请求；
- Zygote进程fork出新的子进程，即App进程；
- App进程，通过Binder IPC向sytem_server进程发起attachApplication请求；
- AMS所在的SystemServer进程在收到请求后，进行一系列准备工作后，再通过binder IPC向App进程发送scheduleLaunchActivity请求；
- App进程的binder线程（ApplicationThread）在收到请求后，通过handler向主线程发送LAUNCH_ACTIVITY消息；
- 主线程在收到Message后，通过发射机制创建目标Activity，并回调Activity.onCreate()等方法。
- 说明了一个Activity的启动流程， 重点在于把握Binder的通信原理，接着弄清楚APP进程，SystemServer进程，Zygote进程是怎么互相通信的
好了，文章基本上就到这里，Activity启动详细流程的分析就到此完毕了！，如有地方不对或者有不同理解的可以提出来
有需要文中完整代码的同学 可以 私信发送 “底层源码” 即可 免费获取
现在私信还可以获得 更多《Android 学习笔记＋源码解析＋面试视频》
最后我想说：
对于程序员来说，要学习的知识内容、技术有太多太多，要想不被环境淘汰就只有不断提升自己，从来都是我们去适应环境，而不是环境来适应我们
技术是无止境的，你需要对自己提交的每一行代码、使用的每一个工具负责，不断挖掘其底层原理，才能使自己的技术升华到更高的层面
Android 架构师之路还很漫长，与君共勉
