一：Android处理Power按键长按操作
在Framework层中，Android4.x对Power键（KeyEvent.KEYCODE_POWER）的操作，我们从PhoneWindowManager开始分析，在分析前我这里打印了该方法的堆栈调用信息。大家可以参考一下。
public long interceptKeyBeforeDispatching(WindowState win, KeyEvent event, int policyFlags) {
......
android.util.Log.d("BILL",android.util.Log.getStackTraceString(new Throwable()));
......
}
1-13 19:35:32.458 D/BILL ( 718): Java.lang.Throwable
01-13 19:35:32.458 D/BILL ( 718): at com.android.internal.policy.impl.PhoneWindowManager.interceptKeyBeforeDispatching(PhoneWindowManager.java:2224)
01-13 19:35:32.458 D/BILL ( 718): at com.android.server.wm.InputMonitor.interceptKeyBeforeDispatching(InputMonitor.java:501)
01-13 19:35:32.458 D/BILL ( 718): at com.android.server.input.InputManagerService.interceptKeyBeforeDispatching(InputManagerService.java:1383)
01-13 19:35:32.458 D/BILL ( 718): at dalvik.system.NativeStart.run(Native Method)
调用流程如下(只贴出关键代码）：
interceptKeyBeforeDispatching()-->interceptPowerKeyDown()-->mPowerLongPress.run()
1>
public long interceptKeyBeforeDispatching(WindowState win, KeyEvent event, int policyFlags) {
......
case KeyEvent.KEYCODE_POWER: { result &= ~ACTION_PASS_TO_USER; if (down) { mImmersiveModeConfirmation.onPowerKeyDown(isScreenOn, event.getDownTime(), isImmersiveMode(mLastSystemUiFlags)); if (isScreenOn && !mPowerKeyTriggered && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) { mPowerKeyTriggered = true; mPowerKeyTime = event.getDownTime(); interceptScreenshotChord(); } ITelephony telephonyService = getTelephonyService(); boolean hungUp = false; if (telephonyService != null) { try { if (telephonyService.isRinging()) { // Pressing Power while there's a ringing incoming // call should silence the ringer. telephonyService.silenceRinger(); /// M: [ALPS00093981] @{ } else if ((isScreenOn || mScreenOffReason == OFF_BECAUSE_OF_PROX_SENSOR) /// @} && (mIncallPowerBehavior & Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP) != 0 && telephonyService.isOffhook()) { // Otherwise, if "Power button ends call" is enabled, // the Power button will hang up any current active call. hungUp = telephonyService.endCall(); } } catch (RemoteException ex) { Log.w(TAG, "ITelephony threw RemoteException", ex); } } interceptPowerKeyDown(!isScreenOn || hungUp || mVolumeDownKeyTriggered || mVolumeUpKeyTriggered); } else { mPowerKeyTriggered = false; cancelPendingScreenshotChordAction(); if (interceptPowerKeyUp(canceled || mPendingPowerKeyUpCanceled)) { result = (result & ~ACTION_WAKE_UP) | ACTION_GO_TO_SLEEP; } mPendingPowerKeyUpCanceled = false; } break; }
......
}
注！红色为判断长按(down)，蓝色为判断短按(up)。
2>
private void interceptPowerKeyDown(boolean handled) { mPowerKeyHandled = handled; if (!handled) { mHandler.postDelayed(mPowerLongPress, ViewConfiguration.getGlobalActionKeyTimeout()); } }
3>
private final Runnable mPowerLongPress = new Runnable() { ...... case LONG_PRESS_POWER_GLOBAL_ACTIONS: mPowerKeyHandled = true; if (!performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false)) { performAuditoryFeedbackForAccessibilityIfNeed(); } sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS); showGlobalActionsDialog(); break; case LONG_PRESS_POWER_SHUT_OFF: case LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM: mPowerKeyHandled = true; performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false); sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS); mWindowManagerFuncs.shutdown(resolvedBehavior == LONG_PRESS_POWER_SHUT_OFF); break; ...... };
注：上述代码中下划线即弹出（关机、重启、飞行模式等选项）的对话框。
从前一篇博文我们知道，当用户长按Power键时会弹出（关机、重启，飞行模式等选项）对话框，我们点击关机，则会弹出关机确认对话框。那么从选项对话框到关机确认对话框又是一个什么流程呢。下面我们在简单分析一下：
showGlobalActionsDialog()-->showDialog()-->handleShow()-->createDialog()-->onPress()-->shutdown()
PhoneWindowManager.Java void showGlobalActionsDialog() { ...... mGlobalActions.showDialog(keyguardShowing, isDeviceProvisioned()); ...... } GlobalActions.java public void showDialog(boolean keyguardShowing, boolean isDeviceProvisioned) { ...... handleShow(); ...... } private void handleShow() { ...... mDialog = createDialog(); ...... } private GlobalActionsDialog createDialog(){ ...... mItems = new ArrayList<Action>(); // first: power off mItems.add( new SinglePressAction( com.Android.internal.R.drawable.uirom_ic_lock_power_off, R.string.global_action_power_off) { public void onPress() { // shutdown by making sure radio and power are handled accordingly. mWindowManagerFuncs.shutdown(true); } public boolean onLongPress() { mWindowManagerFuncs.rebootSafeMode(true); return true; } public boolean showDuringKeyguard() { return true; } public boolean showBeforeProvisioning() { return true; } }); ...... } 上述代码中的mWindowManagerFuncs实际上是WindowManagerService的对象，该对象有PhoneWindowManager的init的方法传入GlobalActions的构造函数中，并在上述代码中进行调用。下面这一行代码是调用的关键代码。 mPolicy.init(mContext, WindowManagerService.this, WindowManagerService.this);
下面是弹出“关机确认对话框”的堆栈： 01-16 18:08:21.497 D/bill ( 720): java.lang.Throwable
01-16 18:08:21.497 D/bill ( 720): at com.android.server.power.ShutdownThread.shutdown(ShutdownThread.java:175)
01-16 18:08:21.497 D/bill ( 720): at com.android.server.wm.WindowManagerService.shutdown(WindowManagerService.java:5783)01-16 18:08:21.497 D/bill ( 720):at com.android.internal.policy.impl.GlobalActions$2.onPress(GlobalActions.java:352)//WindowManagerService实现了接口WindowsManagerFuncs
01-16 18:08:21.497 D/bill ( 720): at com.android.internal.policy.impl.GlobalActions.onClick(GlobalActions.java:581)
01-16 18:08:21.497 D/bill ( 720): at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:952)
01-16 18:08:21.497 D/bill ( 720): at android.widget.AdapterView.performItemClick(AdapterView.java:299)
01-16 18:08:21.497 D/bill ( 720): at android.widget.AbsListView.performItemClick(AbsListView.java:1152)
01-16 18:08:21.497 D/bill ( 720): at android.widget.AbsListView$PerformClick.run(AbsListView.java:3014)
01-16 18:08:21.497 D/bill ( 720): at android.widget.AbsListView$3.run(AbsListView.java:3865)
01-16 18:08:21.497 D/bill ( 720): at android.os.Handler.handleCallback(Handler.java:808)
01-16 18:08:21.497 D/bill ( 720): at android.os.Handler.dispatchMessage(Handler.java:103)
01-16 18:08:21.497 D/bill ( 720): at android.os.Looper.loop(Looper.java:193)
01-16 18:08:21.497 D/bill ( 720): at android.os.HandlerThread.run(HandlerThread.java:61)
从这里（shutdown()）我们正式进入关机流程的关键。
shutdown()<ShutdownThread.java> --->shutdownInner() --->beginShutdownSequence（）--->run()--->rebootOrShutdown()--->lowLevelShutdown()<PowerManagerService.java>---> 源码来自：https://github.com/android/platform_frameworks_base/blob/master/services/java/com/android/server/power/ShutdownThread.java
[java] view plain copy print ? public static void shutdown(final Context context, boolean confirm) { mReboot = false; mRebootSafeMode = false; shutdownInner(context, confirm); } 注！
参数2：confir;关机操作前是否需要用户进行确认 static void shutdownInner(final Context context, boolean confirm) { // ensure that only one thread is trying to power down. // any additional calls are just returned synchronized (sIsStartedGuard) { if (sIsStarted) { Log.d(TAG, "Request to shutdown already running, returning."); return; } } final int longPressBehavior = context.getResources().getInteger( com.android.internal.R.integer.config_longPressOnPowerBehavior);
//longPressBehavior的值标示当前长按Power操作意向（关机、重启。。。） final int resourceId = mRebootSafeMode ? com.android.internal.R.string.reboot_safemode_confirm : (longPressBehavior == 2 ? com.android.internal.R.string.shutdown_confirm_question : com.android.internal.R.string.shutdown_confirm); Log.d(TAG, "Notifying thread to start shutdown longPressBehavior=" + longPressBehavior); if (confirm) { final CloseDialogReceiver closer = new CloseDialogReceiver(context); if (sConfirmDialog != null) { sConfirmDialog.dismiss(); } sConfirmDialog = new AlertDialog.Builder(context) .setTitle(mRebootSafeMode ? com.android.internal.R.string.reboot_safemode_title : com.android.internal.R.string.power_off) .setMessage(resourceId) .setPositiveButton(com.android.internal.R.string.yes, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { beginShutdownSequence(context); } }) .setNegativeButton(com.android.internal.R.string.no, null) .create(); closer.dialog = sConfirmDialog; sConfirmDialog.setOnDismissListener(closer); sConfirmDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG); sConfirmDialog.show(); } else { beginShutdownSequence(context); } } 注：上述代码中，如果需要用户确认关机操作，则会弹出对话框，在对话框的确认按钮被触发时，调用beginShutdownSequence（）方法继续关机流程。如果无需用户确认，则直接调用beginShutdownSequence（）进入下一个关机流程节点。
在beginShutdownSequence（）有些手机厂商常常会在这里添加一些定制功能，例如在对话框中添加“下次快速开机”，定制关机动画等等。随后会根据不同平台进行讲解。下面这张图是Android原生系统的关机画面（对应下面加粗显示的代码）：
private static void beginShutdownSequence (Context context) { synchronized (sIsStartedGuard) { if (sIsStarted) { Log.d(TAG, "Shutdown sequence already running, returning."); return; } sIsStarted = true; } // throw up an indeterminate system dialog to indicate radio is // shutting down. ProgressDialog pd = new ProgressDialog(context); pd.setTitle(context.getText(com.android.internal.R.string.power_off)); pd.setMessage(context.getText(com.android.internal.R.string.shutdown_progress)); pd.setIndeterminate(true); pd.setCancelable(false); pd.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG); pd.show(); sInstance.mContext = context; sInstance.mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE); // make sure we never fall asleep again sInstance.mCpuWakeLock = null; try { sInstance.mCpuWakeLock = sInstance.mPowerManager.newWakeLock( PowerManager.PARTIAL_WAKE_LOCK, TAG + "-cpu");① sInstance.mCpuWakeLock.setReferenceCounted(false);② sInstance.mCpuWakeLock.acquire(); ③ } catch (SecurityException e) { Log.w(TAG, "No permission to acquire wake lock", e); sInstance.mCpuWakeLock = null; } // also make sure the screen stays on for better user experience sInstance.mScreenWakeLock = null;④ if (sInstance.mPowerManager.isScreenOn()) { try { sInstance.mScreenWakeLock = sInstance.mPowerManager.newWakeLock( PowerManager.FULL_WAKE_LOCK, TAG + "-screen"); sInstance.mScreenWakeLock.setReferenceCounted(false); sInstance.mScreenWakeLock.acquire(); } catch (SecurityException e) { Log.w(TAG, "No permission to acquire wake lock", e); sInstance.mScreenWakeLock = null; } } // start the thread that initiates shutdown sInstance.mHandler = new Handler() { }; sInstance.start();⑤ } 注解！
①上述红色代码中的作用主要是为了防止手机进入休眠状态，从代码中我们看到，此时通过PowerManager的newWakeLock方法生成了PowerManager.WakeLock对象。newWakeLock（）是PowerManager中最为常用的方法，该对象是一种锁机制，通过该对象可以控制设备的电源状态。在生成WakeLock实例时通过第一个参数的传入只开控制获取不同的WakeLock，主要是不同的lock对CPU，屏幕，键盘灯有不同的影响。如下：
PARTIAL_WAKE_LOCK:保持CPU 运转，屏幕和键盘灯有可能是关闭的。SCREEN_DIM_WAKE_LOCK：保持CPU 运转，允许保持屏幕显示但有可能是灰的，允许关闭键盘灯SCREEN_BRIGHT_WAKE_LOCK：保持CPU 运转，允许保持屏幕高亮显示，允许关闭键盘灯FULL_WAKE_LOCK：保持CPU 运转，保持屏幕高亮显示，键盘灯也保持亮度
②Wake Lock 是一种锁的机制，只要有人拿着这个锁，系统九五案发进入休眠，可以被用户动态程序和内核获得，这个锁可以使有超时的或者是没有超时的，超时的锁会在时间过去以后自动解锁。如果没有锁了，或者超时了，内核就会启动休眠的那套机制来进入休眠。PowerManager.WakeLock有加锁和解锁的两种状态，加锁的方式有两种，一种是永久的锁住，这样的锁除非是显示的放开，否则是不会解锁的，所以这种锁用起来要非常小心，第二种锁是超时锁，这种锁会在锁住一段时间后自动解锁。
sInstance.mCpuWakeLock.setReferenceCounted(false);是设置锁的方式为永久的锁住。
③sInstance.mCpuWakeLock.acquire(); 加锁 ④上述蓝色代码的作用是为了保证用户体验，保持屏幕、键盘的亮度 ⑤接着启动关机线程，进入关机流程的下一个节点。 /** * Makes sure we handle the shutdown gracefully. * Shuts off power regardless of radio and bluetooth state if the alloted time has passed. */ public void run() { BroadcastReceiver br = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { actionDone();//这里用于接受关机广播，actionDone（）方法主要是防止应用程序取消关机操作。 } }; /* * Write a system property in case the system_server reboots before we * get to the actual hardware restart. If that happens, we'll retry at * the beginning of the SystemServer startup. */ { String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : ""); SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason); } /* * If we are rebooting into safe mode, write a system property * indicating so. */ if (mRebootSafeMode) { SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1"); } Log.i(TAG, "Sending shutdown broadcast..."); // First send the high-level shut down broadcast. mActionDone = false; Intent intent = new Intent(Intent.ACTION_SHUTDOWN); intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND); mContext.sendOrderedBroadcastAsUser(intent, UserHandle.ALL, null, br, mHandler, 0, null, null);//发送关机广播 final long endTime = SystemClock.elapsedRealtime() + MAX_BROADCAST_TIME; synchronized (mActionDoneSync) { while (!mActionDone) { long delay = endTime - SystemClock.elapsedRealtime(); if (delay <= 0) { Log.w(TAG, "Shutdown broadcast timed out"); break; } try { mActionDoneSync.wait(delay); } catch (InterruptedException e) { } } } Log.i(TAG, "Shutting down activity manager..."); final IActivityManager am = ActivityManagerNative.asInterface(ServiceManager.checkService("activity")); if (am != null) { try { am.shutdown(MAX_BROADCAST_TIME);//关闭ActivityManagerService } catch (RemoteException e) { } } Log.i(TAG, "Shutting down package manager..."); final PackageManagerService pm = (PackageManagerService) ServiceManager.getService("package"); if (pm != null) { pm.shutdown();//关闭PackageManagerService服务 } // 关闭Radios shutdownRadios(MAX_RADIO_WAIT_TIME); // Shutdown MountService to ensure media is in a safe state IMountShutdownObserver observer = new IMountShutdownObserver.Stub() { public void onShutDownComplete(int statusCode) throws RemoteException { Log.w(TAG, "Result code " + statusCode + " from MountService.shutdown"); actionDone(); } }; Log.i(TAG, "Shutting down MountService"); // Set initial variables and time out time. mActionDone = false; final long endShutTime = SystemClock.elapsedRealtime() + MAX_SHUTDOWN_WAIT_TIME; synchronized (mActionDoneSync) { try { final IMountService mount = IMountService.Stub.asInterface( ServiceManager.checkService("mount")); if (mount != null) { mount.shutdown(observer);//关闭MountService } else { Log.w(TAG, "MountService unavailable for shutdown"); } } catch (Exception e) { Log.e(TAG, "Exception during MountService shutdown", e); } while (!mActionDone) { long delay = endShutTime - SystemClock.elapsedRealtime(); if (delay <= 0) { Log.w(TAG, "Shutdown wait timed out"); break; } try { mActionDoneSync.wait(delay); } catch (InterruptedException e) { } } } rebootOrShutdown(mReboot, mRebootReason); } 最后调用rebootOrShutdown（） public static void rebootOrShutdown(boolean reboot, String reason) { if (reboot) { Log.i(TAG, "Rebooting, reason: " + reason); PowerManagerService.lowLevelReboot(reason); Log.e(TAG, "Reboot failed, will attempt shutdown instead"); } else if (SHUTDOWN_VIBRATE_MS > 0) { // vibrate before shutting down Vibrator vibrator = new SystemVibrator(); try { vibrator.vibrate(SHUTDOWN_VIBRATE_MS);//关机震动 } catch (Exception e) { // Failure to vibrate shouldn't interrupt shutdown. Just log it. Log.w(TAG, "Failed to vibrate during shutdown.", e); } // vibrator is asynchronous so we need to wait to avoid shutting down too soon. try { Thread.sleep(SHUTDOWN_VIBRATE_MS); } catch (InterruptedException unused) { } } // Shutdown power Log.i(TAG, "Performing low-level shutdown..."); PowerManagerService.lowLevelShutdown();//关闭电源 } } /** * Low-level function turn the device off immediately, without trying * to be clean. Most people should use {@link ShutdownThread} for a clean shutdown. */ public static void lowLevelShutdown() { SystemProperties.set("sys.powerctl", "shutdown");//这里通过修改Android属性进行关机 } 注：上述代码中，红色加粗部分为关机关键代码，我也可以通过adb 命令进行修改Android系统的属性进行关机，具体命令如下
adb shell setprop sys.powerctl shutdown
