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本文我们现在主要分析一下android系统对HOME按键的响应过程#xff0c;HOME按键事件是属于系统级别的按键事件监听#xff0c;而在Android系统中#xff0c;系统级别的按键处理逻辑都在PhoneWindowManager这个类中。
一、interceptKeyBeforeDispatching方法分发按键事…前言
本文我们现在主要分析一下android系统对HOME按键的响应过程HOME按键事件是属于系统级别的按键事件监听而在Android系统中系统级别的按键处理逻辑都在PhoneWindowManager这个类中。
一、interceptKeyBeforeDispatching方法分发按键事件
1、PhoneWindowManager的dispatchUnhandledKey方法是最早收到系统级别的按键事件的。 frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java public class PhoneWindowManager implements WindowManagerPolicy {Overridepublic KeyEvent dispatchUnhandledKey(IBinder focusedToken, KeyEvent event, int policyFlags) {KeyEvent fallbackEvent null;if ((event.getFlags() KeyEvent.FLAG_FALLBACK) 0) {final KeyCharacterMap kcm event.getKeyCharacterMap();final int keyCode event.getKeyCode();final int metaState event.getMetaState();final boolean initialDown event.getAction() KeyEvent.ACTION_DOWN event.getRepeatCount() 0;// Check for fallback actions specified by the key character map.final FallbackAction fallbackAction;if (initialDown) {fallbackAction kcm.getFallbackAction(keyCode, metaState);} else {fallbackAction mFallbackActions.get(keyCode);}if (fallbackAction ! null) {if (DEBUG_INPUT) {Slog.d(TAG, Fallback: keyCode fallbackAction.keyCode metaState Integer.toHexString(fallbackAction.metaState));}final int flags event.getFlags() | KeyEvent.FLAG_FALLBACK;fallbackEvent KeyEvent.obtain(event.getDownTime(), event.getEventTime(),event.getAction(), fallbackAction.keyCode,event.getRepeatCount(), fallbackAction.metaState,event.getDeviceId(), event.getScanCode(),flags, event.getSource(), event.getDisplayId(), null);//在这里进一步触发interceptFallback方法if (!interceptFallback(focusedToken, fallbackEvent, policyFlags)) {fallbackEvent.recycle();fallbackEvent null;}if (initialDown) {mFallbackActions.put(keyCode, fallbackAction);} else if (event.getAction() KeyEvent.ACTION_UP) {mFallbackActions.remove(keyCode);fallbackAction.recycle();}}}return fallbackEvent;}private boolean interceptFallback(IBinder focusedToken, KeyEvent fallbackEvent,int policyFlags) {int actions interceptKeyBeforeQueueing(fallbackEvent, policyFlags);if ((actions ACTION_PASS_TO_USER) ! 0) {//进一步调用interceptKeyBeforeDispatchinglong delayMillis interceptKeyBeforeDispatching(focusedToken, fallbackEvent, policyFlags);if (delayMillis 0) {return true;}}return false;}
}PhoneWindowManager的dispatchUnhandledKey方法会继续触发另一个关键方法interceptFallback而interceptFallback方法又会进一步调用interceptKeyBeforeDispatching方法。
2、PhoneWindowManager的interceptKeyBeforeDispatching方法如下所示。
public class PhoneWindowManager implements WindowManagerPolicy {private final SparseArrayDisplayHomeButtonHandler mDisplayHomeButtonHandlers new SparseArray();Overridepublic long interceptKeyBeforeDispatching(IBinder focusedToken, KeyEvent event,int policyFlags) {final boolean keyguardOn keyguardOn();final int keyCode event.getKeyCode();//按键编码final int repeatCount event.getRepeatCount();final int metaState event.getMetaState();final int flags event.getFlags();final boolean down event.getAction() KeyEvent.ACTION_DOWN;final boolean canceled event.isCanceled();final int displayId event.getDisplayId();//屏幕设备idfinal long key_consumed -1;...代码省略...switch(keyCode) {case KeyEvent.KEYCODE_HOME://系统主要是在这里对HOME按键事件进行响应的//从缓存集合中获取HandlerDisplayHomeButtonHandler handler mDisplayHomeButtonHandlers.get(displayId);if (handler null) {//如果没有缓存则创建Handler并添加到缓存集合中handler new DisplayHomeButtonHandler(displayId);mDisplayHomeButtonHandlers.put(displayId, handler);}return handler.handleHomeButton(focusedToken, event);case KeyEvent.KEYCODE_MENU://菜单按键事件...代码省略...break;case KeyEvent.KEYCODE_APP_SWITCH://应用切换按键事件...代码省略...return key_consumed;...代码省略...}if (isValidGlobalKey(keyCode) mGlobalKeyManager.handleGlobalKey(mContext, keyCode, event)) {return key_consumed;}if ((metaState KeyEvent.META_META_ON) ! 0) {return key_consumed;}return 0;}interceptKeyBeforeDispatching方法会通过switch的各个case分支分别来响应各种按键事件我们这里主要关注HOME按键事件的响应过程系统首先从mDisplayHomeButtonHandlers集合中获取DisplayHomeButtonHandler类型的缓存对象如果不存在缓存对象则创建DisplayHomeButtonHandler对象并添加到集合中反正最终会调用DisplayHomeButtonHandler的handleHomeButton方法。
3、DisplayHomeButtonHandler是PhoneWindowManager的内部类handleHomeButton方法如下所示。
public class PhoneWindowManager implements WindowManagerPolicy {private class DisplayHomeButtonHandler {private final int mDisplayId;private boolean mHomeDoubleTapPending;private boolean mHomePressed;private boolean mHomeConsumed;private final Runnable mHomeDoubleTapTimeoutRunnable new Runnable() {Overridepublic void run() {if (mHomeDoubleTapPending) {mHomeDoubleTapPending false;handleShortPressOnHome(mDisplayId);}}};DisplayHomeButtonHandler(int displayId) {mDisplayId displayId;}int handleHomeButton(IBinder focusedToken, KeyEvent event) {final boolean keyguardOn keyguardOn();final int repeatCount event.getRepeatCount();final boolean down event.getAction() KeyEvent.ACTION_DOWN;//是否是按下事件final boolean canceled event.isCanceled();//一个按键事件大多都有两种Action按下(ACTION_DOWN)和抬起(ACTION_UP)//!down意味着只有用户触发按键抬起的时候这里才会做响应回到首页if (!down) {if (mDisplayId DEFAULT_DISPLAY) {cancelPreloadRecentApps();}mHomePressed false;if (mHomeConsumed) {mHomeConsumed false;return -1;}if (canceled) {Log.i(TAG, Ignoring HOME; event canceled.);return -1;}if (mDoubleTapOnHomeBehavior ! DOUBLE_TAP_HOME_NOTHING) {mHandler.removeCallbacks(mHomeDoubleTapTimeoutRunnable); // just in casemHomeDoubleTapPending true;mHandler.postDelayed(mHomeDoubleTapTimeoutRunnable,ViewConfiguration.getDoubleTapTimeout());return -1;}//为了避免阻塞输入管道这里通过Handler的post方法切换到了主线程mHandler.post(() - handleShortPressOnHome(mDisplayId));return -1;}...代码省略...return -1;}}private void handleShortPressOnHome(int displayId) {// Turn on the connected TV and switch HDMI input if were a HDMI playback device.final HdmiControl hdmiControl getHdmiControl();if (hdmiControl ! null) {hdmiControl.turnOnTv();}// If theres a dream running then use home to escape the dream// but dont actually go home.if (mDreamManagerInternal ! null mDreamManagerInternal.isDreaming()) {mDreamManagerInternal.stopDream(false /*immediate*/);return;}// Go home!launchHomeFromHotKey(displayId);}
}handleHomeButton方法首先获取按键的Action类型是否为按下并且进行了条件判断只有当按键抬起的时候才会触发返回首页的相关操作为了避免阻塞输入管道这里通过Handler的post方法将当前线程切换到了主线程并进一步调用handleShortPressOnHome方法该方法又进一步调用launchHomeFromHotKey方法。
4、PhoneWindowManager的launchHomeFromHotKey方法如下所示。
public class PhoneWindowManager implements WindowManagerPolicy {void launchHomeFromHotKey(int displayId) {launchHomeFromHotKey(displayId, true /* awakenFromDreams */, true /*respectKeyguard*/);}/*** A home key - launch home action was detected. Take the appropriate action* given the situation with the keyguard.*/void launchHomeFromHotKey(int displayId, final boolean awakenFromDreams,final boolean respectKeyguard) {if (respectKeyguard) {if (isKeyguardShowingAndNotOccluded()) {return;}if (!isKeyguardOccluded() mKeyguardDelegate.isInputRestricted()) {//当处于锁屏模式的时候首先应该解锁然后才能打开首页mKeyguardDelegate.verifyUnlock(new OnKeyguardExitResult() {Overridepublic void onKeyguardExitResult(boolean success) {if (success) {startDockOrHome(displayId, true /*fromHomeKey*/, awakenFromDreams);}}});return;}}//判断最近任务是否可见if (mRecentsVisible) {try {//如果最近任务视图可见则会先停止应用切换功能ActivityManager.getService().stopAppSwitches();} catch (RemoteException e) {}if (awakenFromDreams) {awakenDreams();}//隐藏最近任务hideRecentApps(false, true);} else {//否则打开首页startDockOrHome(displayId, true /*fromHomeKey*/, awakenFromDreams);}}}launchHomeFromHotKey方法先是判断当前是否处于锁屏状态如果处于锁屏状体则必须先解锁然后才能打开首页。然后会判断最近任务是否可见
如果可见则会调用AMS的stopAppSwitches方法停止应用切换功能该方法的目的主要是为了暂停后台打开Activity的操作避免打扰用户的操作.比如这时候我们在后台打开一个新的App那么由于要回到home页面所以需要先延时打开。在停止应用切换功能之后还会调用hideRecentApps隐藏最近任务。如果最近任务不可见则会直接调用startDockOrHome方法打开首页。
二、startDockOrHome方法打开首页
1、PhoneWindowManager的startDockOrHome方法如下所示。
public class PhoneWindowManager implements WindowManagerPolicy {void startDockOrHome(int displayId, boolean fromHomeKey, boolean awakenFromDreams,String startReason) {try {//先停止应用切换功能ActivityManager.getService().stopAppSwitches();} catch (RemoteException e) {}//关闭系统当前存在的各种弹窗sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);if (awakenFromDreams) {awakenDreams();}if (!mHasFeatureAuto !isUserSetupComplete()) {Slog.i(TAG, Not going home because user setup is in progress.);return;}//创建桌面意图对象Intent dock createHomeDockIntent();if (dock ! null) {//如果桌面意图对象不为空则打开该意图对象try {if (fromHomeKey) {dock.putExtra(WindowManagerPolicy.EXTRA_FROM_HOME_KEY, fromHomeKey);}startActivityAsUser(dock, UserHandle.CURRENT);return;} catch (ActivityNotFoundException e) {}}if (DEBUG_WAKEUP) {Log.d(TAG, startDockOrHome: startReason startReason);}//调用ATMS的startHomeOnDisplay方法打开首页mActivityTaskManagerInternal.startHomeOnDisplay(mCurrentUserId, startReason,displayId, true /* allowInstrumenting */, fromHomeKey);}
}startDockOrHome方法先是调用ActivityManager.getService().stopAppSwitches()暂停掉应用切换然后调用sendCloseSystemWindows方法关闭系统当前存在的各种弹窗然后调用createHomeDockIntent方法创建桌面意图对象如果创建成功则直接打开该意图对象否则会调用ATMS的startHomeOnDisplay方法打开首页。
2.1、先来看下ActivityManagerService的stopAppSwitches方法。
public class ActivityManagerService extends IActivityManager.Stubimplements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback, ActivityManagerGlobalLock {public ActivityTaskManagerService mActivityTaskManager;Overridepublic void stopAppSwitches() {mActivityTaskManager.stopAppSwitches();}
}ActivityManagerService的stopAppSwitches方法什么都没做只是进一步调用ActivityTaskManagerService的stopAppSwitches方法。 2.2、ActivityTaskManagerService 的stopAppSwitches方法。
public class ActivityTaskManagerService extends IActivityTaskManager.Stub {//停止后台打开应用的操作Overridepublic void stopAppSwitches() {mAmInternal.enforceCallingPermission(STOP_APP_SWITCHES, stopAppSwitches);synchronized (mGlobalLock) {mAppSwitchesState APP_SWITCH_DISALLOW;//纪录当前时间mLastStopAppSwitchesTime SystemClock.uptimeMillis();mH.removeMessages(H.RESUME_FG_APP_SWITCH_MSG);mH.sendEmptyMessageDelayed(H.RESUME_FG_APP_SWITCH_MSG, RESUME_FG_APP_SWITCH_MS);}}
}
