<未完成，待续>
分析 Activity 启动和显示过程不是单纯为走一遍函数调用流程，而是更好的应用到工作中，理解系统中一些关键方法、对象的初始化时间，先后顺序，以及每个类，方法背后的作用和目的，对工作中分析应用性能问题、优化启动时间有重要的意义。
比如：
- 应用进程何时创建？
- 应用的 Application 对象什么创建，它的 onCreate() 方法什么时候调用？
- ActivityThread 和 Activity 中 attach() 方法调用时序、作用和区别？
- Activity 对象什么时候创建，它的 onCreate() 方法如何执行？
-
onResume() 方法和 Activity 在屏幕上显示的时序关系？
//在 ApplicationThread 的scheduleLaunchActivity() 方法中创建了 ActivityClientRecord 对象
public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident, ActivityInfo info, ......) {
ActivityClientRecord r = new ActivityClientRecord();
r.token = token;
r.ident = ident;
r.intent = intent;
......
sendMessage(H.LAUNCH_ACTIVITY, r);
}
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
ActivityInfo aInfo = r.activityInfo;
if (r.packageInfo == null) {
r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
Context.CONTEXT_INCLUDE_CODE);
}
ComponentName component = r.intent.getComponent();
if (component == null) {
component = r.intent.resolveActivity(
mInitialApplication.getPackageManager());
r.intent.setComponent(component);
}
if (r.activityInfo.targetActivity != null) {
component = new ComponentName(r.activityInfo.packageName,
r.activityInfo.targetActivity);
}
Activity activity = null;
try {
java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
// 创建 activity 实例
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
} catch (Exception e) {
......
}
try {
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if (activity != null) {
Context appContext = createBaseContextForActivity(r, activity);
......
//执行 Activity 的 attach() 方法，此方法中会把AmS 的 token 传递过去
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);
......
int theme = r.activityInfo.getThemeResource();
if (theme != 0) {
activity.setTheme(theme);
}
......
// 把创建的 activity 赋值到 ActivityClientRecord 对象中，之后就能通过 token 来找到对应的 Activity
r.activity = activity;
......
}
......
mActivities.put(r.token, r);
}
return activity;
}
Activity 和 AmS 之间如何对应识别的?
ActivityThread.java 中有一个ArrayMap 类型的成员变量：
final ArrayMap<IBinder, ActivityClientRecord> mActivities = new ArrayMap<>();
它是在 performLaunchActivity() 中添加应用进程中所有的 Activity 对象 ：
mActivities.put(r.token, r);
之后 AmS 调用 Activity 生命周期方法时都会传入 token 参数来告诉应用进程当前应该操作哪一个 Activity，例如回调 onResume() 方法：
public final void scheduleResumeActivity(IBinder token, int processState,
boolean isForward, Bundle resumeArgs) {
updateProcessState(processState, false);
sendMessage(H.RESUME_ACTIVITY, token, isForward ? 1 : 0);
}
public final ActivityClientRecord performResumeActivity(IBinder token,
boolean clearHide) {
ActivityClientRecord r = mActivities.get(token);
......
}
ActivityThread attach()作用：
ActivityThread 的 attach() 方法在 ActivityThread 的 main() 方法中调用，会将 ActivityThread 中的 ApplicationThread(Binder 对象)通过 attachApplication() 附着给AmS，这样 AmS 就可以控制Activity的生命周期，其中 attachApplication() 方法做了三件事：
准备数据, 创建一个ProcessRecord app的对象记录一个进程的所有信息, 对各个字段进行赋值.
调用mAppThread这个Binder对象的bindApplication(ProcessRecord app)方法, 把记录着进程信息的对象ProcessRecord传给ApplicationThread处理,
在bindApplication()内通过Handler mH发送一个"BIND_APPLICATION"消息让mH处理.mH处理"BIND_APPLICATION"时调用handleBindApplication(),
在里面创建Applicaiton app对象， 调用Application的onCreate(), 到这里ActivityThread的handleBindApplication()方法执行完毕.在ActivityManagerService的attachApplication()处理完第二步之后, 调用mStackSupervisor.attachApplicationLocked(app), 在里面再调用realStartActivityLocked(),
里面再调用app.thread.scheduleLaunchActivity()， 也就是mAppThread的scheduleLaunchActivity(), 在ApplicationThread的scheduleLaunchActivity()内，
发送一个"LAUNCH_ACTIVITY"消息, mH处理"LAUNCH_ACTIVITY"时调用handleLaunchActivity(), handleLaunchActivity()分两步, 第一步调performLaunchActivity(),
创建Activity的对象， 依次调用它的onCreate(), onStart(). 第二步调handleResumeActivity(), 调用Activity对象的onResume()。
Activity attach() 作用：
Activity 的 attach() 方法在 performLaunchActivity() 中创建好 Activity 对象后调用， 会在 onCreate() 之前会将创建出来的 ContextImpl 对象 attach 到 Activity 上，并创建 PhoneWindow 对象等。
final void attach(Context context, ActivityThread aThread,
Instrumentation instr, IBinder token, int ident,
Application application, Intent intent, ActivityInfo info,
CharSequence title, Activity parent, String id,
NonConfigurationInstances lastNonConfigurationInstances,
Configuration config, String referrer, IVoiceInteractor voiceInteractor,
Window window, ActivityConfigCallback activityConfigCallback) {
attachBaseContext(context);
mFragments.attachHost(null /*parent*/);
mWindow = new PhoneWindow(this, window, activityConfigCallback);
mWindow.setWindowControllerCallback(this);
mWindow.setCallback(this);//用来分发触摸事件
mWindow.setOnWindowDismissedCallback(this);
mWindow.getLayoutInflater().setPrivateFactory(this);
if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
mWindow.setSoftInputMode(info.softInputMode);
}
if (info.uiOptions != 0) {
mWindow.setUiOptions(info.uiOptions);
}
mUiThread = Thread.currentThread();
mMainThread = aThread;
mInstrumentation = instr;
mToken = token;
mIdent = ident;
mApplication = application;
mIntent = intent;
mReferrer = referrer;
mComponent = intent.getComponent();
mActivityInfo = info;
mTitle = title;
mParent = parent;
mEmbeddedID = id;
mLastNonConfigurationInstances = lastNonConfigurationInstances;
if (voiceInteractor != null) {
if (lastNonConfigurationInstances != null) {
mVoiceInteractor = lastNonConfigurationInstances.voiceInteractor;
} else {
mVoiceInteractor = new VoiceInteractor(voiceInteractor, this, this,
Looper.myLooper());
}
}
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
mToken, mComponent.flattenToString(),
(info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
if (mParent != null) {
mWindow.setContainer(mParent.getWindow());
}
mWindowManager = mWindow.getWindowManager();
mCurrentConfig = config;
mWindow.setColorMode(info.colorMode);
}
AppWindowContainerController.java
NOTIFY_WINDOWS_DRAWN
AppWindowContainerController.java
-- updateReportedVisibilityLocked()
-- reportWindowsDrawn() {
mHandler.sendMessage(mHandler.obtainMessage(H.NOTIFY_WINDOWS_DRAWN));
}
public void handleMessage(Message msg) {
switch (msg.what) {
case NOTIFY_WINDOWS_DRAWN:
if (mListener == null) {
return;
}
if (DEBUG_VISIBILITY) Slog.v(TAG_WM, "Reporting drawn in "
+ AppWindowContainerController.this.mToken);
mListener.onWindowsDrawn(msg.getWhen());
ActivityRecord.java
--onWindowsDrawn()
reportLaunchTimeLocked() 打印ActivityManager: Displayed com.example.sprd.myapplication999/.MainActivity: +231ms
触摸事件分发
DecorView.java
public boolean dispatchTouchEvent(MotionEvent ev) {
final Window.Callback cb = mWindow.getCallback();
return cb != null && !mWindow.isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev);
}
这里的Window.Callback其实就是Activity:
public class Activity extends ContextThemeWrapper implements Window.Callback,...{
即回调到Activity.dispatchTouchEvent()
