这儿分析ActivityThread Main函数后的流程
ActivityThread.main()（代码只抓主线）
1 应用启动的入口
public static void main(String[] args) {
Looper.prepareMainLooper();#UI线程Looper的启动
.....
ActivityThread thread = new ActivityThread();
thread.attach(false, startSeq);#*
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
....
Looper.loop();
}
2 attach()
private void attach(boolean system, long startSeq) {
# startSeq ActivityManager 信息传递标志
if(!system){#我们分析的分支 非系统应用
final IActivityManager mgr = ActivityManager.getService();
try {
# 这个头部声明并初始化 final ApplicationThread mAppThread = new ApplicationThread();
# IApplicationThread.Stub 接口 接收来之ActivityManager 所有信息
# 如bindApplication
mgr.attachApplication(mAppThread, startSeq);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}else{
...
}
}
建立完通信进制开始处理接收来自ActivityManager流程指令
1、bindApplication
public final void bindApplication(String processName, ApplicationInfo appInfo,...){
....
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.enableBinderTracking = enableBinderTracking;
data.trackAllocation = trackAllocation;
data.restrictedBackupMode = isRestrictedBackupMode;
data.persistent = persistent;
data.config = config;
data.compatInfo = compatInfo;
data.initProfilerInfo = profilerInfo;
data.buildSerial = buildSerial;
data.autofillCompatibilityEnabled autofillCompatibilityEnabled;
sendMessage(H.BIND_APPLICATION, data);# 由 mH handler 处理
}
找到H handler 中 case BIND_APPLICATION: handleBindApplication(data);分支
handleBindApplication(data)
private void handleBindApplication(AppBindData data) {
....
app = data.info.makeApplication(data.restrictedBackupMode,null);# 1 application 和context 在这初始化，
mInstrumentation.callApplicationOnCreate(app);#调用Application OnCreate
}
至此绑定Application流程，当然我省略了我不懂或者我还没研究透的 接下来时启动Activity 在android28 之前ApplicationThread中的handlerLaunchActivity，不过在这之后改成事务启动，所有Activity几个重要流程都通过
@Override
public void scheduleTransaction(ClientTransacttransaction) throws RemoteException {
ActivityThread.this.scheduleTransaction(transaction);
}
最终也由 H handler处理
case EXECUTE_TRANSACTION:
final ClientTransaction transaction = (ClientTransaction) msg.obj;
mTransactionExecutor.execute(transaction);
....
break;
这儿简单的说明启动handlerActivity的流程
TransactionExecutor.execute()-> executeLifecycleState(transaction)-> lifecycleItem.execute(mTransactionHandler, token, mPendingActions)->LaunchActivityItem.execute()->ActivityThread.handleLaunchActivity()
2、 handleLaunchActivity()
public Activity handleLaunchActivity(ActivityClientRecord r,
PendingTransactionActions pendingActions, Intent customIntent) {
final Activity a = performLaunchActivity(r, customIntent); #1
}
1
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
ContextImpl appContext = createBaseContextForActivity(r);
activity = mInstrumentation.newActivity(cl, component.getClassName(), r.intent);
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);
mInstrumentation.callActivityOnCreate(activity, r.state);
#调用Activity onCreate
}
通handleLaunchActivity 一样接下来 ApplicationThread 会收到handleStartActivity()、handleResumeActivity()、handlePauseActivity()、handleStopActivity()、handleDestroyActivity()...
应用启动大致流程分析到这儿。
下面分析Activity的界面 PhoneWindow,DecorView,ViewRootImpl 的关系（现在也说不清）
还是在上文的基础上继续分析下去
PhoneWindow的创建
handleLaunchActivity()这个方法里比较重要的两点一个是我们一直都在使用的onCreate()的调用，在这个之前attach这个方法更为重要
final void attach(Context context, ActivityThread aThread,...){
attachBaseContext(context);#Activity context
mWindow = new PhoneWindow(this, window, activityConfigCallback);
mWindow.setWindowControllerCallback(this);
...# window实例
#Activity 参数配置
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
mToken, mComponent.flattenToString(),
(info.flagActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
# window 设置WindowManager
}
通常我们在onCreate里做的一个比较重要动作就是setContentView(int id)通过源码会发现最终调用的是Phonewindow的setContentView()现在我们分析下这个方法做了哪些工作
DecorView的创建
public void setContentView(int layoutResID) {
if (mContentParent == null) {
installDecor();#1 初始化DecorView
} else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
mContentParent.removeAllViews();
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
getContext());
transitionTo(newScene);
} else {
mLayoutInflater.inflate(layoutResID, mContentParent);
#2解析布局文件通过反射实例化相对应的view
}
mContentParent.requestApplyInsets();
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
mContentParentExplicitlySet = true;
}
注释1
private void installDecor() {
if (mDecor == null) {
mDecor = generateDecor(-1);#实例化
mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
mDecor.setIsRootNamespace(true);
if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
}
} else {
mDecor.setWindow(this);
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor);
#除导航栏状态栏，内容都显示在这
}
}
ViewRootImpl创建
handleStartActivity()这个方法对我们分析比较不重要跳过 handleResumeActivity() 我们知道这个方法过后内容才会显示出来，分析下都做了哪些工作
public void handleResumeActivity(IBinder token, boolean finalStateRequest, boolean isForward, String reason) {
// TODO Push resumeArgs into the activity for consideration
final ActivityClientRecord r = performResumeActivity(tokenfinalStateRequest, reason);
#调用 Activity的onResume()
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();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
....
if (a.mVisibleFromClient) {
if (!a.mWindowAdded) {
a.mWindowAdded = true;
wm.addView(decor, l);
#1
} else {
// The activity will get a callback for this {@link LayoutParams} change
// earlier. However, at that time the decor will not be set (this is set
// in this method), so no action will be taken. This call ensures the
// callback occurs with the decor set.
a.onWindowAttributesChanged(l);
}
}
}
}
跟踪 addView()-> mGlobal.addView()
WindowManagerGlobal
public void addView(View view, ViewGroup.LayoutParams params, Display display, Window parentWindow) {
...
root = new ViewRootImpl(view.getContext(), display);
# ViewRootImpl创建
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);
try {
root.setView(view, wparams, panelParentView);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
if (index >= 0) {
removeViewLocked(index, true);
}
throw e;
}
}
ViewRootImpl 的 setView()
ViewRootImpl
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
...
requestLayout();//此处会先进行一次测量
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,getHostVisibility(), mDisplay.getDisplayId(),
mWinFrame,mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,mAttachInfo.mOutsets, mAttachInfo.mDisplayCutout, mInputChannel);
#1 mWindow 接收来自WMS的相关指令
#与WMS建立Session通信
mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
Looper.myLooper());
#创建接收事件的Receiver 后续的点击事件都由此收到并进行分发
}
ViewRootImpl::W{
...
public void windowFocusChanged(boolean hasFocus, boolean inTouchMode)
# 进行页面的显示
...
}
requestLayout()->scheduleTraversals() 看到这个scheduleTraversals()是不是一切都明朗起来了
趁热打铁继续分析scheduleTraversals()做的工作
void scheduleTraversals() {
if (!mTraversalScheduled) {
mTraversalScheduled = true;
mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
#往loope里发送屏障信息，looper会遍历整个列表直到有相应关于异步的信息（屏障信息没有target，loop循环时发现没有target的信息，会继续搜索队列中的异步信息，直到查找到优先处理）
mChoreographer.postCallback(
Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
#发送更新视图的异步信息，该信息会优先被处理
#1、通过handler发送traversal信息
#2、Choreographer.scheduleFrameLocked()->scheduleVsyncLocked();-> mDisplayEventReceiver.scheduleVsync();注册时间片段
#3、FrameDisplayEventReceiver.onVsync()收到刷新信息， scheduleVsync();继续注册
#4、发送刷新信息-> doFrame(mTimestampNanos, mFrame);
#5、doCallbacks(Choreographer.CALLBACK_TRAVERSAL,frameTimeNanos);->c.run()->doTraversal()
if (!mUnbufferedInputDispatch) {
scheduleConsumeBatchedInput();
}
notifyRendererOfFramePending();
pokeDrawLockIfNeeded();
}
}
