启动流程
Activity startActivity
@Override
public void startActivity(Intent intent) {
startActivity(intent, null);
}
@Override
public void startActivity(Intent intent, Bundle options) {
if (options != null) {
startActivityForResult(intent, -1, options);
} else {
// Note we want to go through this call for compatibility with
// applications that may have overridden the method.
startActivityForResult(intent, -1);
}
}
public void startActivityForResult(Intent intent, int requestCode) {
startActivityForResult(intent, requestCode, null);
}startActivityForResult
public void startActivityForResult(Intent intent, int requestCode, Bundle options) {
//一般的Activity其mParent为null，mParent常用在ActivityGroup中，ActivityGroup已废弃
if (mParent == null) {
//这里会启动新的Activity，核心功能都在mMainThread.getApplicationThread()中完成
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode, options);
if (ar != null) {
//发送结果，即onActivityResult会被调用
mMainThread.sendActivityResult(
mToken, mEmbeddedID, requestCode, ar.getResultCode(),
ar.getResultData());
}
if (requestCode >= 0) {
// If this start is requesting a result, we can avoid making
// the activity visible until the result is received. Setting
// this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
// activity hidden during this time, to avoid flickering.
// This can only be done when a result is requested because
// that guarantees we will get information back when the
// activity is finished, no matter what happens to it.
mStartedActivity = true;
}
final View decor = mWindow != null ? mWindow.peekDecorView() : null;
if (decor != null) {
decor.cancelPendingInputEvents();
}
} else {
//在ActivityGroup内部的Activity调用startActivity的时候会走到这里，内部处理逻辑和上面是类似的
if (options != null) {
mParent.startActivityFromChild(this, intent, requestCode, options);
} else {
// Note we want to go through this method for compatibility with
// existing applications that may have overridden it.
mParent.startActivityFromChild(this, intent, requestCode);
}
}
}
Instrumentation execStartActivity
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, Activity target,
Intent intent, int requestCode, Bundle options) {
//核心功能在这个whoThread中完成，其内部scheduleLaunchActivity方法用于完成activity的打开
IApplicationThread whoThread = (IApplicationThread) contextThread;
if (mActivityMonitors != null) {
synchronized (mSync) {
//先查找一遍看是否存在这个activity
final int N = mActivityMonitors.size();
for (int i=0; i<N; i++) {
final ActivityMonitor am = mActivityMonitors.get(i);
if (am.match(who, null, intent)) {
//如果找到了就跳出循环
am.mHits++;
//如果目标activity无法打开，直接return
if (am.isBlocking()) {
return requestCode >= 0 ? am.getResult() : null;
}
break;
}
}
}
}
try {
intent.migrateExtraStreamToClipData();
intent.prepareToLeaveProcess();
//这里才是真正打开activity的地方，核心功能在whoThread中完成。
int result = ActivityManagerNative.getDefault()
.startActivity(whoThread, who.getBasePackageName(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()),
token, target != null ? target.mEmbeddedID : null,
requestCode, 0, null, null, options);
//这个方法是专门抛异常的，它会对结果进行检查，如果无法打开activity，
//则抛出诸如ActivityNotFoundException类似的各种异常
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
}
return null;
}
ActivityManagerNative#getDefault
static public IActivityManager getDefault() {
return ActivityManager.getService();
}ActivityManager#getService
public static IActivityManager getService() {
return IActivityManagerSingleton.get();
}
private static final Singleton<IActivityManager> IActivityManagerSingleton =
new Singleton<IActivityManager>() {
@Override
protected IActivityManager create() {
//获取系统服务
final IBinder b = ServiceManager.getService(Context.ACTIVITY_SERVICE);
final IActivityManager am = IActivityManager.Stub.asInterface(b);
return am;
}
};IActivityManger 的实现类是 ActivityManagerService， startActivity 方法
@Override
public int startActivity(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {
return mActivityTaskManager.startActivity(caller, callingPackage, intent, resolvedType,
resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions);
}ActivityTaskManagerService#startactivity
@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());
}ActivityStarter#excute
int execute() {
try {
// TODO(b/64750076): Look into passing request directly to these methods to allow
// for transactional diffs and preprocessing.
if (mRequest.mayWait) {
return startActivityMayWait(mRequest.caller, mRequest.callingUid,
mRequest.callingPackage, mRequest.realCallingPid, mRequest.realCallingUid,
mRequest.intent, mRequest.resolvedType,
mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,
mRequest.resultWho, mRequest.requestCode, mRequest.startFlags,
mRequest.profilerInfo, mRequest.waitResult, mRequest.globalConfig,
mRequest.activityOptions, mRequest.ignoreTargetSecurity, mRequest.userId,
mRequest.inTask, mRequest.reason,
mRequest.allowPendingRemoteAnimationRegistryLookup,
mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart);
} else {
return startActivity(mRequest.caller, mRequest.intent, mRequest.ephemeralIntent,
mRequest.resolvedType, mRequest.activityInfo, mRequest.resolveInfo,
mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,
mRequest.resultWho, mRequest.requestCode, mRequest.callingPid,
mRequest.callingUid, mRequest.callingPackage, mRequest.realCallingPid,
mRequest.realCallingUid, mRequest.startFlags, mRequest.activityOptions,
mRequest.ignoreTargetSecurity, mRequest.componentSpecified,
mRequest.outActivity, mRequest.inTask, mRequest.reason,
mRequest.allowPendingRemoteAnimationRegistryLookup,
mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart);
}
} finally {
onExecutionComplete();
}
}最终会调到 ApplicationThread scheduleLaunchActivity
public final void scheduleLaunchActivity() {
// 通过 Handler 发送 LAUNCH_ACTIVITY
sendMessage(H.LAUNCH_ACTIVITY, r);
}ActivityThread#handleLaunchActivity
private void handleLaunchActivity() {
// 执行启动 Activity
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
// resume activity
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);
} else {
}
}ActivityThread#performLaunchActivity
private performLaunchActivity() {
// Activity 信息初始化
// 创建 context
ContextImpl appContext = createBaseContextForActivity(r);
Activity activity = null;
try {
java.lang.ClassLoader cl = appContext.getClassLoader();
// 构建 Activity
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
}catch(Exception e){
}
try {
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if(activity != null){
activity.attach();
// 通过 Instrumentation 执行 Activity onCreate
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
}else {
mInstrumentation.callActivityOnCreate(activity, r.state);
}
if (!r.activity.mFinished) {
// Activity onStart
activity.performStart();
}
// 通过 Instrumentation 执行 Activity onRestoreInstanceState
if (!r.activity.mFinished) {
if (r.isPersistable()) {
if (r.state != null || r.persistentState != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
r.persistentState);
}
} else if (r.state != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
}
}
// 通过 Instrumentation 执行 Activity onPostCreeate
if (!r.activity.mFinished) {
if (r.isPersistable()) {
mInstrumentation.callActivityOnPostCreate(activity, r.state,
r.persistentState);
}else {
mInstrumentation.callActivityOnPostCreate(activity, r.state);
}
}
}
return activity;
}final void handleResumeActivity() {
r = performResumeActivity();
if(r != null) {
final Activity a = r.activity;
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow();
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager();
if (a.mVisibleFromClient) {
if (!a.mWindowAdded) {
a.mWindowAdded = true;
// window
wm.addView(decor, l);
}
}
}
}
}resume 之后才开始添加View
public final ActivityClientRecord performResumeActivity() {
if (r != null && !r.activity.mFinished) {
try {
// 处理等待的 Intent
if (r.pendingIntents != null) {
deliverNewIntents(r, r.pendingIntents);
r.pendingIntents = null;
}
// 处理等待的 result
if (r.pendingResults != null) {
deliverResults(r, r.pendingResults);
r.pendingResults = null;
}
// 执行 resume
r.activity.performResume();
}
}
}Instrumentation
public Activity newActivity(){
return (Activity)cl.loadClass(className).newInstance();
}private void callActivityOnCreate(){
prePerformCreate(activity);
activity.performCreate(icicle);
postPerformCreate(activity);
}Activity
final void performCreate() {
restoreHasCurrentPermissionRequest(icicle);
// 调用 onCreate
onCreate(icicle);
mActivityTransitionState.readState(icicle);
performCreateCommon();
}final void performStart() {
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
mInstrumentation.callActivityOnStart(this);
mActivityTransitionState.enterReady(this);
}final void performResume() {
// 执行 restart
performRestart();
mInstrumentation.callActivityOnResume(this);
}final void performRestart() {
if (mStopped) {
mStopped = false;
mInstrumentation.callActivityOnRestart(this);
// 执行 start
performStart();
}
}Instrumentation
public void callActivityOnStart() {
activity.onStart();
}public void callActivityOnResume() {
activity.mResumed = true;
activity.onResume();
}public void callActivityOnRestart() {
activity.onRestart();
}
参考
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