app_watchdogd

app_watchdogd.sh is used to automatically relaunch an Android APP which is killed or crashed.

app_watchdogd.sh can be run in /data/data/com.domain.appname/files/ or /system/xbin/ .

If run app_watchdogd.sh without su -c , even your device is rooted, adb shell cat /proc/APP_WATCHDOG_SH_PID/oom_adj will not be -17 but 0, Android system will kill app_watchdogd.sh process if not smaller than 0 when memory is low, so you need

su -c /data/data/com.domain.appname/files/app_watchdogd.sh &

and this one line command above is obviously better than

/data/data/com.domain.appname/files/app_watchdogd.sh &
manually find APP_WATCHDOG_SH_PID with `ps | grep /system/bin/sh | grep -c poll_sched)`
su -c echo -12 > /proc/APP_WATCHDOG_SH_PID/oom_adj
su -c chmod -r /proc/APP_WATCHDOG_SH_PID/oom_adj

Usage

For sure your device

• rooted
• install-supersu

shell test

• $1 pkg_or_kill: pkg e.g. com.domain.appname means enable watchdogd; or just kill means disable watchdogd
• $2 activity: e.g. MainActivity if pkg; null if kill
• $3 timeout_sec: e.g. 5 if pkg; null if kill

adb remount
adb push app_watchdogd.sh system/xbin/
adb shell su -c system/xbin/app_watchdogd.sh com.domain.appname MainActivity 5 &
adb shell su -c system/xbin/app_watchdogd.sh kill

react-native APP

Copy as android/app/src/main/assets/app_watchdogd.sh .

utils.js :

import AndroidShell from '@flyskywhy/react-native-android-shell';

export function enableAppWatchdogd({
  shPath = '/system/xbin/app_watchdogd.sh',
  pkg,
  activity = 'MainActivity',
  timeoutSec = 5,
}) {
  AndroidShell.executeCommand(
    'su -c ' + shPath + ' ' + pkg + ' ' + activity + ' ' + timeoutSec + ' &',
    () => {},
  );
}

export function disableAppWatchdogd({
  shPath = '/system/xbin/app_watchdogd.sh',
  callback = () => {},
}) {
  AndroidShell.executeCommand('su -c ' + shPath + ' kill', callback);
}

Navigation.js :

if (Platform.OS !== 'web') {
  var RNFS = require('react-native-fs');
}
import AndroidShell from '@flyskywhy/react-native-android-shell';
import RNExitApp from 'react-native-exit-app';
import * as utils from '../utils';

const shPath = `${RNFS.DocumentDirectoryPath}/app_watchdogd.sh`;

class Navigation extends Component {

...

  componentDidMount() {
    this.enableAppWatchdogd();
  }

  enableAppWatchdogd = async () => {
    if (Platform.OS === 'android') {
      if (!(await RNFS.exists(shPath))) {
        await RNFS.copyFileAssets('app_watchdogd.sh', shPath); // /data/data/com.domain.appname/files/app_watchdogd.sh
      }

      AndroidShell.executeCommand(
        'su -c dumpsys window | grep mCurrentFocus',
        (activity) => {
          let a = activity
            .replace(/\n/, '')
            .replace(/^.* .* /, '')
            .replace('}', ''); // com.domain.appname/com.domain.appname.MainActivity
          let pkg = a.replace(/\/.*/, ''); // com.domain.appname
          utils.enableAppWatchdogd({ // if APP exit abnormally (killed or crashed), will be relaunched
            shPath,
            pkg,
          });
        },
      );

      // above have a small bug: after adb install then first launch, pkg could be `com.android.systemui` (from mCurrentFocus)
      // below works well if you can `import {applicationId} from 'expo-application'`
      // utils.enableAppWatchdogd({ // if APP exit abnormally (killed or crashed), will be relaunched
      //   shPath,
      //   pkg: applicationId,
      // });
    }
  };

  onBackPress = async () => {
    if (USER_PRESS_ANDROID_BACK_KEY_TWICE) {
      if (Platform.OS === 'android') {
        utils.disableAppWatchdogd({ // if APP exit normally (by user), will disable watchdogd
          shPath,
          callback: RNExitApp.exitApp,
        });
      } else {
        RNExitApp.exitApp();
      }
    }
  };

...

}

pure Android APP

Copy as android/app/src/main/assets/app_watchdogd.sh when building, save as /data/data/com.domain.appname/files/app_watchdogd.sh when running, then su -c /data/data/com.domain.appname/files/app_watchdogd.sh & from Java.