case LAUNCH_ACTIVITY: {    final ActivityClientRecord r = (ActivityClientRecord) msg.obj;    r.packageInfo = getPackageInfoNoCheck(            r.activityInfo.applicationInfo, r.compatInfo);    handleLaunchActivity(r, null, "LAUNCH_ACTIVITY");

private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {    Activity a = performLaunchActivity(r, customIntent);    if (a != null) {        r.createdConfig = new Configuration(mConfiguration);        reportSizeConfigurations(r);        Bundle oldState = r.state;        handleResumeActivity(r.token, false, r.isForward,                !r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);    }}

比较重要的两个方法 一个 performLaunchActivity()，另一个是handleResumeActivity()。

performLaunchActivity()中：

attach( )   // 创建window 其与Activity的显示相关

onCreate();   // setContentView( ) 解析xml中view 并与decorview产生关联

handleResumeActivity()中：

执行activity中的onResume方法，将WindowManager将DecorView添加到Window中

将decorview添加到ViewRootImpl中，并有decorview执行测量、布局、绘制等操作。