我之前分析了Activity的启动流程,若不熟悉的可以看上篇文章App启动——Activity的启动流程
由之前文章我们可以知道最终Activity进入ActivityThread并发送名为LAUNCH_ACTIVITY的消息,最终会走到handleMessage方法
case LAUNCH_ACTIVITY: {
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);
} break;
handleLaunchActivity源码:这里后期还会回来分析
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) {
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
Bundle oldState = r.state;
//2
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;
}
//代码省略
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
//代码省略
}
r.paused = true;
}
//代码省略
}
}
performLaunchActivity源码上篇已经说过不再阐述,实际调用的是Activity的onCreate方法
handleResumeActivity源码分析
final void handleResumeActivity(...) {
ActivityClientRecord r = performResumeActivity(token, clearHide);
}
public final ActivityClientRecord performResumeActivity(..){
//代码省略
r.activity.performResume();
if (!r.activity.mFinished && r.startsNotResumed) {
try {
r.activity.mCalled = false;
mInstrumentation.callActivityOnPause(r.activity);
if (r.isPreHoneycomb()) {
r.state = oldState;
}
//代码省略
}
if (r.window == null && !a.mFinished && willBeVisible) {
//代码省略
if (a.mVisibleFromClient) {
a.mWindowAdded = true;
wm.addView(decor, l);
}
}
}
r.activity.performResume实际调用的是Activity的Resume
final void performResume() {
performRestart();
//代码省略
// Now really resume, and install the current status bar and menu.
mCalled = false;
//代码省略
mFragments.dispatchResume();
mFragments.execPendingActions();
//代码省略
mInstrumentation.callActivityOnResume(this);
}
performRestart源码
final void performRestart() {
//代码省略
if (mStopped) {//停止的状态
mStopped = false;
//代码省略
mCalled = false;
mInstrumentation.callActivityOnRestart(this);
performStart();
}
}
mInstrumentation.callActivityOnRestart(this)实际调用的是activity的onRestart方法
performStart()源码分析;
final void performStart() {
//代码省略
mInstrumentation.callActivityOnStart(this);
}
实际调用的是Instrumentation中的callActivityOnStrart方法
public void callActivityOnStart(Activity activity) {
activity.onStart();
}
我们可以看到performStart实际调用的是onStart方法
现在我们回到r.activity.performResume方法中,看 mInstrumentation.callActivityOnResume(this);
public void callActivityOnResume(Activity activity) {
activity.mResumed = true;
activity.onResume();
//代码省略
}
实际调用的是Activity的onResume方法
我们这时候再回到handleResumeActivity中看 wm.addView(decor, l);的源码
public interface ViewManager
{
public void addView(View view, ViewGroup.LayoutParams params);
public void updateViewLayout(View view, ViewGroup.LayoutParams params);
public void removeView(View view);
}
可以看到实际是个抽象类,我们看wm是怎么被实例化的
//我们会发现这个方法会创建一个WindowManager
ViewManager wm = a.getWindowManager();
public WindowManager getWindowManager() {
return mWindowManager;
}
我们都知道WindowManager的实现类是PhoneWindow,查看其getWindowManager源码,我们会发现,实际这个走的是Window中的getWindowManager()方法
//实际最终创建的是WindowManagerImpl这个实例,查看这个源码中的addView方法
mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this);
@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
}
WindowMangerImp中的addView源码分析
ViewRootImpl root;
root = new ViewRootImpl(view.getContext(), display);
try {
//设置view进去
root.setView(view, wparams, panelParentView);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
if (index >= 0) {
removeViewLocked(index, true);
}
throw e;
}
调用的ViewRootImpl中的setView方法,调用其中的 requestLayout()-> scheduleTraversals();->mTraversalRunnable->doTraversal->performMeasure->view的measure-.onMeasure方法这时候我们就看到了onMeasure实际是在onResume方法之后调用的
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