源码解析之-基于Android10.0的startActivity
Posted Android编程精选
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了源码解析之-基于Android10.0的startActivity相关的知识，希望对你有一定的参考价值。
Python实战社群
Java实战社群
长按识别下方二维码，按需求添加
扫码关注添加客服
进Python社群▲
扫码关注添加客服
进Java社群▲
作者丨张潮州
来源丨android技术堆栈
StartActivity流程概览
1、在APP进程发起startActivity
在Activity中的startActivityForResult()调用Instrumentation的execStartActivity()：
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode, options);
在Instrumentation的execStartActivity()调用ATMS的startActivity()：
int result = ActivityTaskManager.getService()
.startActivity(whoThread, who.getBasePackageName(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()),
token, target != null ? target.mEmbeddedID : null,
requestCode, 0, null, options);
其中ATMS实例是从AMS中获得的：
/** @hide */
public static IActivityTaskManager getService() {
return IActivityTaskManagerSingleton.get();
}
@UnsupportedAppUsage(trackingBug = 129726065)
private static final Singleton<IActivityTaskManager> IActivityTaskManagerSingleton =
new Singleton<IActivityTaskManager>() {
@Override
protected IActivityTaskManager create() {
final IBinder b = ServiceManager.getService(Context.ACTIVITY_TASK_SERVICE);
return IActivityTaskManager.Stub.asInterface(b);
}
};
2、在ATMS进程发起startActivity
在ATMS的startActivityAsUser()调用ActivityStarter的execute()：
// TODO: Switch to user app stacks here.
return getActivityStartController().obtainStarter(intent, "startActivityAsUser")
.setCaller(caller)
.setCallingPackage(callingPackage)
.setResolvedType(resolvedType)
.setResultTo(resultTo)
.setResultWho(resultWho)
.setRequestCode(requestCode)
.setStartFlags(startFlags)
.setProfilerInfo(profilerInfo)
.setActivityOptions(bOptions)
.setMayWait(userId)
.execute();
在ActivityStarter的startActivityUnchecked()调用RootActivityContainer的resumeFocusedStacksTopActivities()：
mRootActivityContainer.resumeFocusedStacksTopActivities();
在RootActivityContainer的resumeFocusedStacksTopActivities()调用ActivityStack 的resumeTopActivityUncheckedLocked()：
boolean result = false;
if (targetStack != null && (targetStack.isTopStackOnDisplay()
|| getTopDisplayFocusedStack() == targetStack)) {
result = targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);
}
2.1、onPause()
在ActivityStack的startPausingLocked()调用ClientLifecycleManager的scheduleTransaction()，此处操作对应生命周期的onPause()流程：
mService.getLifecycleManager().scheduleTransaction(prev.app.getThread(),
prev.appToken, PauseActivityItem.obtain(prev.finishing, userLeaving,
prev.configChangeFlags, pauseImmediately));
2.2、onCreate()
或者先在ActivityStack的resumeTopActivityInnerLocked()调用ActivityStackSupervisor的startSpecificActivityLocked()：
mStackSupervisor.startSpecificActivityLocked(next, true, false);
然后在ActivityStackSupervisor的realStartActivityLocked()调用ClientLifecycleManager的scheduleTransaction()，此处操作对应生命周期的onCreate()流程：
// Schedule transaction.
mService.getLifecycleManager().scheduleTransaction(clientTransaction);
2.3、安排事务到APP进程
在ClientLifecycleManager的scheduleTransaction()中调用ClientTransaction的schedule()：
void scheduleTransaction(ClientTransaction transaction) throws RemoteException {
final IApplicationThread client = transaction.getClient();
transaction.schedule();
}
3、回到APP进程
在ClientTransaction的schedule()中调用ActivityThread内部类ApplicationThread的scheduleTransaction()：
public void schedule() throws RemoteException {
mClient.scheduleTransaction(this);
}
在ApplicationThread的scheduleTransaction()调用了ActivityThread也就是其父类ClientTransactionHandler的scheduleTransaction()：
@Override
public void scheduleTransaction(ClientTransaction transaction) throws RemoteException {
ActivityThread.this.scheduleTransaction(transaction);
}
在ClientTransactionHandler的scheduleTransaction()，通过H发送了EXECUTE_TRANSACTION消息：
/** Prepare and schedule transaction for execution. */
void scheduleTransaction(ClientTransaction transaction) {
transaction.preExecute(this);
sendMessage(ActivityThread.H.EXECUTE_TRANSACTION, transaction);
}
在H中接收EXECUTE_TRANSACTION消息，并调用了TransactionExecutor的execute()：
case EXECUTE_TRANSACTION:
final ClientTransaction transaction = (ClientTransaction) msg.obj;
mTransactionExecutor.execute(transaction);
if (isSystem()) {
// Client transactions inside system process are recycled on the client side
// instead of ClientLifecycleManager to avoid being cleared before this
// message is handled.
transaction.recycle();
}
// TODO(lifecycler): Recycle locally scheduled transactions.
break;
3.1、onPause()
如果对应的是onPause()流程，将会在TransactionExecutor的execute()调用executeLifecycleState()，并继续调用ActivityLifecycleItem也就是子类PauseActivityItem的execute()：
lifecycleItem.execute(mTransactionHandler, token, mPendingActions);
在PauseActivityItem的execute()调用ClientTransactionHandler也就是子类ActivityThread的handlePauseActivity()：
@Override
public void execute(ClientTransactionHandler client, IBinder token,
PendingTransactionActions pendingActions) {
Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityPause");
client.handlePauseActivity(token, mFinished, mUserLeaving, mConfigChanges, pendingActions,
"PAUSE_ACTIVITY_ITEM");
Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);
}
而后将继续在ActivityThread的performPauseActivityIfNeeded()调用Instrumentation的callActivityOnPause()：
mInstrumentation.callActivityOnPause(r.activity);
而后调用Activity的performPause()：
public void callActivityOnPause(Activity activity) {
activity.performPause();
}
最后调用Activity的onPause()：
final void performPause() {
dispatchActivityPrePaused();
mDoReportFullyDrawn = false;
mFragments.dispatchPause();
mCalled = false;
onPause();
writeEventLog(LOG_AM_ON_PAUSE_CALLED, "performPause");
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()");
}
dispatchActivityPostPaused();
}
3.2、onCreate()
如果对应的是onCreate()流程，将会在TransactionExecutor的execute()调用executeCallbacks()，并继续调用ClientTransactionItem 也就是子类LaunchActivityItem的execute()：
item.execute(mTransactionHandler, token, mPendingActions);
在LaunchActivityItem的execute()调用ClientTransactionHandler也就是子类ActivityThread的handleLaunchActivity()：
@Override
public void execute(ClientTransactionHandler client, IBinder token,
PendingTransactionActions pendingActions) {
Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
ActivityClientRecord r = new ActivityClientRecord(token, mIntent, mIdent, mInfo,
mOverrideConfig, mCompatInfo, mReferrer, mVoiceInteractor, mState, mPersistentState,
mPendingResults, mPendingNewIntents, mIsForward,
mProfilerInfo, client, mAssistToken);
client.handleLaunchActivity(r, pendingActions, null /* customIntent */);
Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);
}
而后将继续在ActivityThread的performLaunchActivity()调用Instrumentation的newActivity()使用反射来创建Activity实例：
java.lang.ClassLoader cl = appContext.getClassLoader();
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
public Activity newActivity(ClassLoader cl, String className,
Intent intent)
throws InstantiationException, IllegalAccessException,
ClassNotFoundException {
String pkg = intent != null && intent.getComponent() != null
? intent.getComponent().getPackageName() : null;
return getFactory(pkg).instantiateActivity(cl, className, intent);
}
public @NonNull Activity instantiateActivity(@NonNull ClassLoader cl, @NonNull String className,
@Nullable Intent intent)
throws InstantiationException, IllegalAccessException, ClassNotFoundException {
return (Activity) cl.loadClass(className).newInstance();
}
而后继续在ActivityThread的performLaunchActivity()调用Activity的attach()：
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, window, r.configCallback,
r.assistToken);
创建好Activity实例后，将会调用Instrumentation的callActivityOnCreate()：
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity, r.state);
}
而后调用Activity的performCreate()：
public void callActivityOnCreate(Activity activity, Bundle icicle,
PersistableBundle persistentState) {
prePerformCreate(activity);
activity.performCreate(icicle, persistentState);
postPerformCreate(activity);
}
最后调用Activity的onCreate()：
@UnsupportedAppUsage
final void performCreate(Bundle icicle, PersistableBundle persistentState) {
dispatchActivityPreCreated(icicle);
mCanEnterPictureInPicture = true;
restoreHasCurrentPermissionRequest(icicle);
if (persistentState != null) {
onCreate(icicle, persistentState);
} else {
onCreate(icicle);
}
writeEventLog(LOG_AM_ON_CREATE_CALLED, "performCreate");
mActivityTransitionState.readState(icicle);
mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(
com.android.internal.R.styleable.Window_windowNoDisplay, false);
mFragments.dispatchActivityCreated();
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
dispatchActivityPostCreated(icicle);
}
程序员专栏
扫码关注填加客服
长按识别下方二维码进群
近期精彩内容推荐：
在看点这里好文分享给更多人↓↓
以上是关于源码解析之-基于Android10.0的startActivity的主要内容，如果未能解决你的问题，请参考以下文章
Android的PackageManagerService10.0源码解读(AndroidManifest.xml解析)
Android的PackageManagerService10.0源码解读(AndroidManifest.xml解析)
Android的PackageManagerService10.0源码解读(AndroidManifest.xml解析)
基于android10.0源码分析Activity的启动流程