android framework 低电量关机处理流程浅析

一，主要涉及的类

./base/services/java/com/android/server/BatteryService.java
./base/services/java/com/android/server/ShutdownActivity.java
./base/services/java/com/android/server/power/PowerManagerService.java
./base/services/java/com/android/server/power/ShutdownThread.java
./base/core/java/android/os/PowerManager.java

二.BatteryService 监控电池电量等信息

android系统app上层更新显示电池电量信息，主要是靠BatterySerivice不断为其更新数据信息。至于如何更新的，另外的博文有分析。

这里主要分析低电量关机相关流程。

BatteryService中的update方法会间隔时间的不断更新。

                                  // 低电量的时候会弹出对话框并且接着关机。                             private void shutdownIfNoPowerLocked() {                               // shut down gracefully if our battery is critically low and we are not powered.                               // wait until the system has booted before attempting to display the shutdown dialog.                               //从这里的if判断条件可以看出低电量关机条件电量接近0并且没有连接充电。                               if (mBatteryProps.batteryLevel == 0 && !isPoweredLocked(BatteryManager.BATTERY_PLUGGED_ANY)) {                                 mHandler.post(new Runnable() { // the battery is low and battery plugged .                                   @Override                                   public void run() {                                     //跳转到ShutdownActivity.java                                     if (ActivityManagerNative.isSystemReady()) {                                       Intent intent = new Intent(Intent.ACTION_REQUEST_SHUTDOWN);                                       intent.putExtra(Intent.EXTRA_KEY_CONFIRM, false);                                       intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);                                       mContext.startActivityAsUser(intent, UserHandle.CURRENT);                                     }                                   }                                 });                               }                             }

接下来，跳转到ShutdownActivity.java，这个acitivity比较简单，他吧另外的逻辑放在了子线程，直接获得PowerManagerService并调用其中的方法，因此重点是PowerManagerService.java

                                    @Override                             protected void onCreate(Bundle savedInstanceState) {                               super.onCreate(savedInstanceState);                                                          Intent intent = getIntent();                               if(intent==null){return ;} // google do not add this . but i add .                               mReboot = Intent.ACTION_REBOOT.equals(intent.getAction()); //false from the batteryService.java                               mConfirm = intent.getBooleanExtra(Intent.EXTRA_KEY_CONFIRM, false); // false from the BatteryService.java                               Slog.i(TAG, "onCreate(): confirm=" + mConfirm);                                                          Thread thr = new Thread("ShutdownActivity") {                                 @Override                                 public void run() {                                   IPowerManager pm = IPowerManager.Stub.asInterface(                                       ServiceManager.getService(Context.POWER_SERVICE));                                   try {                                     if (mReboot) {                                       pm.reboot(mConfirm, null, false);                                     } else {                                       pm.shutdown(mConfirm, false); //mConfirm ==false                                     }                                   } catch (RemoteException e) {                                   }                                 }                               };                               thr.start();                               finish();                               // Wait for us to tell the power manager to shutdown.                               try {                                 thr.join(); // wait for worker thread to do has job.                               } catch (InterruptedException e) {                               }                             }

接下来，逻辑转移到PowerManagerService中、

                                    /**                              * Shuts down the device.                              *                              * @param confirm If true, shows a shutdown confirmation dialog.                              * @param wait If true, this call waits for the shutdown to complete and does not return.                              */                             @Override // Binder call                             public void shutdown(boolean confirm, boolean wait) {                               mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);                           // u must get get the permission of reboot .                               final long ident = Binder.clearCallingIdentity();                               try {                                 shutdownOrRebootInternal(true, confirm, null, wait);// true ,false ,null,false                               } finally {                                 Binder.restoreCallingIdentity(ident);                               }                             }                                                        private void shutdownOrRebootInternal(final boolean shutdown, final boolean confirm,                                 final String reason, boolean wait) {                               if (mHandler == null || !mSystemReady) {                                 throw new IllegalStateException("Too early to call shutdown() or reboot()");                               }                                                       //看到这里你是否和我一样有点不解？ why: 在ShutdownActivity中，是放在了子线程的，而到了这里继续被放到新的子线程。这样？                               Runnable runnable = new Runnable() {                                 @Override                                 public void run() {                                   synchronized (this) {                                     if (shutdown) {                                       ShutdownThread.shutdown(mContext, confirm);//confirm == false                                     } else {                                       ShutdownThread.reboot(mContext, reason, confirm);                                     }                                   }                                 }                               };                               // ShutdownThread must run on a looper capable of displaying the UI.                               Message msg = Message.obtain(mHandler, runnable) ;                               msg.setAsynchronous(true); //异步消息                               mHandler.sendMessage(msg);                                                          // PowerManager.reboot() is documented not to return so just wait for the inevitable.                           下面这段代码......
                               if (wait) {
                                 synchronized (runnable) {                                   while (true) {                                     try {                                       runnable.wait();                                     } catch (InterruptedException e) {                                     }                                   }                                 }                               }                             }

上面的代码

                                      // ShutdownThread must run on a looper capable of displaying the UI.                               Message msg = Message.obtain(mHandler, runnable) ;                               msg.setAsynchronous(true);                               mHandler.sendMessage(msg);

接下来转到ShutdownThread.java中，

                                    /**                              * Request a clean shutdown, waiting for subsystems to clean up their                              * state etc. Must be called from a Looper thread in which its UI                              * is shown.                              *                              * @param context Context used to display the shutdown progress dialog.                              * @param confirm true if user confirmation is needed before shutting down.                              */                             public static void shutdown(final Context context, boolean confirm) {                               mReboot = false;                               mRebootSafeMode = false;                               shutdownInner(context, confirm);                             }

                                           // shutdown system ... confirm==false                                   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);
                                     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); //shutdown_confirm 您的手机将会关机                                                                      Log.d(TAG, "Notifying thread to start shutdown longPressBehavior=" + longPressBehavior);                                                                      if (confirm) { //低电量关机流程时，confirm==false，因此走else分支                                       final CloseDialogReceiver closer = new CloseDialogReceiver(context);                                       if (sConfirmDialog != null) {                                         sConfirmDialog.dismiss();                                       }                                                                              //Knight 2015.06.15 ####                                       sConfirmDialog = new AlertDialog.Builder(context)                                           .setTitle(mRebootSafeMode                                             ? com.android.internal.R.string.reboot_safemode_title                                             : (mReboot                                               ? com.android.internal.R.string.reboot_title                                               : com.android.internal.R.string.power_off))                                           .setMessage(mReboot                                             ? com.android.internal.R.string.reboot_confirm                                             : 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 { //低电量关机走的流程                                       beginShutdownSequence(context);                                     }                                   }

                                                    private static void beginShutdownSequence(Context context) {                                          // 这部分显得有些多余，因为在进入该方法之前已经调用过下面这段代码了。 xiangxm add comments                                         /*  synchronized (sIsStartedGuard) {                                             if (sIsStarted) {                                               Log.d(TAG, "Shutdown sequence already running, returning.");                                               return;                                             }                                             sIsStarted = true;                                           }*/                                          // check the shutdown animation exists or not.                                           boolean showShutdownAnim = new File("/system/media/shutdownanimation.zip").exists();                                                                               下面的代码，主要是处理当关机的时候显示Dialog，并且显示进度条，以及使用PowerManager.WakeLock 保持cpu和屏幕 
                                       不休眠。 
                                       // throw up an indeterminate system dialog to indicate radio is
                                           // shutting down.                                           ProgressDialog pd = new ProgressDialog(context);                                           Log.d("frank_08_19", "mReboot = " + String.valueOf(mReboot));                                           //frank 08-19                                           if(mReboot){   // reboot progress                                              pd.setTitle(context.getText(com.android.internal.R.string.reboot_wh));                                             pd.setMessage(context.getText(com.android.internal.R.string.reboot_progress));                                           }else{                                              pd.setTitle(context.getText(com.android.internal.R.string.power_off));                                             pd.setMessage(context.getText(com.android.internal.R.string.shutdown_progress));                                           }                                           if (showShutdownAnim && SystemProperties.getBoolean("rw.use.shutdown.movie.wh", false)) {                                             Log.d("frank_09_20", "shutdown animation");                                             SystemProperties.set("debug.shutdown_movie", "2"); //what                                             android.os.SystemProperties.set("service.bootanim.exit", "0");                                             Intent intent=new Intent();                                              intent.setAction("wh_test_func_key"); //do home key                                              context.sendBroadcast(intent);                                                                                     intent.setAction("frank.shutdown.rotation.screen"); //disable gsensor in database                                             context.sendBroadcast(intent);                                                                                     //frank 09-20                                             int shutdown_movie = SystemProperties.getInt("rw.shutdownanim_frank.wh", 0);                                             if(shutdown_movie != 0 )                                             {                                               try{                                                 Thread.sleep(shutdown_movie);                                               }catch(InterruptedException ex){                                               }                                              }                                             android.os.SystemProperties.set("ctl.start", "shutdownanim"); //start shutdown movie                                                                                  } else //if(SystemProperties.getBoolean("rw.show.shutdown.dialog.wh", false))                                           {                                           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");                                             sInstance.mCpuWakeLock.setReferenceCounted(false);//many acqure() only onece release()                                             sInstance.mCpuWakeLock.acquire();                                           } 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;                                           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();                                         }

接下来转到shutdownThread的run方法中，

run方法中，陆续关闭各个service等。后面的部分暂时不做分析。

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