Android 关机FrameWrok层代码调用流程

PowerManager的reboot函数：

/**
     * Reboot the device.  Will not return if the reboot is successful.
     * <p>
     * Requires the {@link android.Manifest.permission#REBOOT} permission.
     * </p>
     *
     * @param reason code to pass to the kernel (e.g., "recovery") to
     *               request special boot modes, or null.
     */
    public void reboot(String reason) {
        try {
            mService.reboot(false, reason, true);
        } catch (RemoteException e) {
        }
    }

而mService的定义如下：

final IPowerManager mService;

mService指向了PowerManagerService的类对象，PowerManagerService的reboot函数定义如下：

/**
     * Reboots the device.
     *
     * @param confirm If true, shows a reboot confirmation dialog.
     * @param reason The reason for the reboot, or null if none.
     * @param wait If true, this call waits for the reboot to complete and does not return.
     */
    @Override // Binder call
    public void reboot(boolean confirm, String reason, boolean wait) {
        mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);

        final long ident = Binder.clearCallingIdentity();
        try {
            shutdownOrRebootInternal(false, confirm, reason, wait);
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
    }

调用了PowerManagerService的shutdownOrRebootInternal函数，如下：

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()");
        }

        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                synchronized (this) {
                    if (shutdown) {
                        ShutdownThread.shutdown(mContext, confirm);
                    } 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);
        mHandler.sendMessage(msg);

        // PowerManager.reboot() is documented not to return so just wait for the inevitable.
        if (wait) {
            synchronized (runnable) {
                while (true) {
                    try {
                        runnable.wait();
                    } catch (InterruptedException e) {
                    }
                }
            }
        }
    }

ShutdownThread的shutdown实现如下：

/**
     * 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);
    }

ShutdownThread的reboot实现如下：

    /**
     * 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 reason code to pass to the kernel (e.g. "recovery"), or null.
     * @param confirm true if user confirmation is needed before shutting down.
     */
    public static void reboot(final Context context, String reason, boolean confirm) {
        mReboot = true;
        mRebootSafeMode = false;
        mRebootReason = reason;
        shutdownInner(context, confirm);
    }

通过这两段代码，可以知道，最后都调用了ShutdownThread类的shutdownInner函数：

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);

        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);
        }
    }

这里主要是处理了是否弹窗的分支，当用户选择“确认”关机后，调用beginShutdownSequence函数：

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");
            sInstance.mCpuWakeLock.setReferenceCounted(false);
            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();
    }