按home键之后,所有activity的启动请求都延迟了5秒,下面我们分析一个系统是怎么做的
void launchHomeFromHotKey(final boolean awakenFromDreams, final boolean respectKeyguard) {
if (respectKeyguard) {
if (isKeyguardShowingAndNotOccluded()) {
// don't launch home if keyguard showing
return;
}
if (!mHideLockScreen && mKeyguardDelegate.isInputRestricted()) {
// when in keyguard restricted mode, must first verify unlock
// before launching home
mKeyguardDelegate.verifyUnlock(new OnKeyguardExitResult() {
@Override
public void onKeyguardExitResult(boolean success) {
if (success) {
try {
ActivityManagerNative.getDefault().stopAppSwitches();
} catch (RemoteException e) {
}
sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);
startDockOrHome(true /*fromHomeKey*/, awakenFromDreams);
}
}
});
return;
}
}
// no keyguard stuff to worry about, just launch home!
try {
ActivityManagerNative.getDefault().stopAppSwitches();
} catch (RemoteException e) {
}
......
}
PhoneWindowManager处理Home键之后调用stopAppSwitches()
@Override
public void stopAppSwitches() {
if (checkCallingPermission(android.Manifest.permission.STOP_APP_SWITCHES)
!= PackageManager.PERMISSION_GRANTED) {
throw new SecurityException("viewquires permission "
+ android.Manifest.permission.STOP_APP_SWITCHES);
}
synchronized(this) {
mAppSwitchesAllowedTime = SystemClock.uptimeMillis()
+ APP_SWITCH_DELAY_TIME;
mDidAppSwitch = false;
mHandler.removeMessages(DO_PENDING_ACTIVITY_LAUNCHES_MSG);
Message msg = mHandler.obtainMessage(DO_PENDING_ACTIVITY_LAUNCHES_MSG);
mHandler.sendMessageDelayed(msg, APP_SWITCH_DELAY_TIME);
}
}
ActivityManagerService收到stopAppSwitches请求后,取消DO_PENDING_ACTIVITY_LAUNCHES_MSG,发送APP_SWITCH_DELAY_TIME,在Stub端将所有的activity启动请求延迟了5秒,这个是Google为了提升用户体验有意为之。