简单分析一下Android恢复出厂设置的流程

代码是Android KK平台的。

1，在设置中，点击恢复出厂设置，一直到最后一个button的时候代码如下：

packages/apps/Settings中MasterClearConfirm.java

    /**
     * The user has gone through the multiple confirmation, so now we go ahead
     * and invoke the Checkin Service to reset the device to its factory-default
     * state (rebooting in the process).
     */
    private Button.OnClickListener mFinalClickListener = new Button.OnClickListener() {


        public void onClick(View v) {
            if (Utils.isMonkeyRunning()) {
                return;
            }


            if (mEraseSdCard) {
                Intent intent = new Intent(ExternalStorageFormatter.FORMAT_AND_FACTORY_RESET);
                intent.setComponent(ExternalStorageFormatter.COMPONENT_NAME);
                getActivity().startService(intent);
            } else {
                getActivity().sendBroadcast(new Intent("android.intent.action.MASTER_CLEAR"));
                // Intent handling is asynchronous -- assume it will happen soon.
            }
        }
    }

不擦除SD卡的时候，可以看到，点击恢复出厂设置按钮后，发送一个广播android.intent.action.MASTER_CLEAR

2，既然广播发送了，那必然有一个接收的地方，接收此广播的地方在

framework/base/services/下 MasterClearReceiver.java

public class MasterClearReceiver extends BroadcastReceiver {
    private static final String TAG = "MasterClear";

    @Override
    public void onReceive(final Context context, final Intent intent) {
        if (intent.getAction().equals(Intent.ACTION_REMOTE_INTENT)) {
            if (!"google.com".equals(intent.getStringExtra("from"))) {
                Slog.w(TAG, "Ignoring master clear request -- not from trusted server.");
                return;
            }
        }

        Slog.w(TAG, "!!! FACTORY RESET !!!");
        // The reboot call is blocking, so we need to do it on another thread.
        Thread thr = new Thread("Reboot") {
            @Override
            public void run() {
                try {
                    RecoverySystem.rebootWipeUserData(context);
                    Log.wtf(TAG, "Still running after master clear?!");
                } catch (IOException e) {
                    Slog.e(TAG, "Can't perform master clear/factory reset", e);
                }
            }
        };
        thr.start();
    }
}

代码很少，可以看到是执行了RecoverySystem.rebootWipeUserData(context)方法，接下来进入这个类中查看

3，

frameworks/base/core/java/android/os/RecoverySystem.java

    /**
     * Reboots the device and wipes the user data partition.  This is
     * sometimes called a "factory reset", which is something of a
     * misnomer because the system partition is not restored to its
     * factory state.
     * Requires the {@link android.Manifest.permission#REBOOT} permission.
     *
     * @param context  the Context to use
     *
     * @throws IOException  if writing the recovery command file
     * fails, or if the reboot itself fails.
     */
    public static void rebootWipeUserData(Context context) throws IOException {
        final ConditionVariable condition = new ConditionVariable();

        Intent intent = new Intent("android.intent.action.MASTER_CLEAR_NOTIFICATION");
        context.sendOrderedBroadcastAsUser(intent, UserHandle.OWNER,
                android.Manifest.permission.MASTER_CLEAR,
                new BroadcastReceiver() {
                    @Override
                    public void onReceive(Context context, Intent intent) {
                        condition.open();
                    }
                }, null, 0, null, null);

        // Block until the ordered broadcast has completed.
        condition.block();

        bootCommand(context, "--wipe_data\n--locale=" + Locale.getDefault().toString());
    }

这里进行重启和擦除，condition.open(), conditon.block(). 由于这个广播是ordered，一次只能进行一个，所以当系统还未准备好的时候，反应会比较慢。

简单分析一下Android恢复出厂设置的流程

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