详解Android 8.0以上系统应用如何保活

最近在做一个埋点的sdk，由于埋点是分批上传的，不是每次都上传，所以会有个进程保活的机制，这也是自研推送的实现技术之一：如何保证Android进程的存活。

对于Android来说，保活主要有以下一些方法：

• 开启前台Service（效果好，推荐）
• Service中循环播放一段无声音频（效果较好，但耗电量高，谨慎使用）
• 双进程守护（Android 5.0前有效）
• JobScheduler（Android 5.0后引入，8.0后失效）
• 1 像素activity保活方案（不推荐）
• 广播锁屏、自定义锁屏（不推荐）
• 第三方推送SDK唤醒（效果好，缺点是第三方接入）

下面是具体的实现方案：

1.监听锁屏广播，开启1个像素的Activity

最早见到这种方案的时候是2015年，有个FM的app为了向投资人展示月活，在Android应用中开启一个1像素的Activity。

由于Activity的级别是比较高的，所以开启1个像素的Activity的方式就可以保证进程是不容易被杀掉的。

具体来说，定义一个1像素的Activity，在该Activity中动态注册自定义的广播。

class OnePixelActivity : AppCompatActivity() {

  private lateinit var br: BroadcastReceiver

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    //设定一像素的activity
    val window = window
    window.setGravity(Gravity.LEFT or Gravity.TOP)
    val params = window.attributes
    params.x = 0
    params.y = 0
    params.height = 1
    params.width = 1
    window.attributes = params
    //在一像素activity里注册广播接受者  接受到广播结束掉一像素
    br = object : BroadcastReceiver() {
      override fun onReceive(context: Context, intent: Intent) {
        finish()
      }
    }
    registerReceiver(br, IntentFilter("finish activity"))
    checkScreenOn()
  }

  override fun onResume() {
    super.onResume()
    checkScreenOn()
  }

  override fun onDestroy() {
    try {
      //销毁的时候解锁广播
      unregisterReceiver(br)
    } catch (e: IllegalArgumentException) {
    }
    super.onDestroy()
  }

  /**
   * 检查屏幕是否点亮
   */
  private fun checkScreenOn() {
    val pm = this@OnePixelActivity.getSystemService(Context.POWER_SERVICE) as PowerManager
    val isScreenOn = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
      pm.isInteractive
    } else {
      pm.isScreenOn
    }
    if (isScreenOn) {
      finish()
    }
  }
}

2， 双进程守护

双进程守护，在Android 5.0前是有效的，5.0之后就不行了。首先，我们定义定义一个本地服务，在该服务中播放无声音乐，并绑定远程服务

class LocalService : Service() {
  private var mediaPlayer: MediaPlayer? = null
  private var mBilder: MyBilder? = null

  override fun onCreate() {
    super.onCreate()
    if (mBilder == null) {
      mBilder = MyBilder()
    }
  }

  override fun onBind(intent: Intent): IBinder? {
    return mBilder
  }

  override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
    //播放无声音乐
    if (mediaPlayer == null) {
      mediaPlayer = MediaPlayer.create(this, R.raw.novioce)
      //声音设置为0
      mediaPlayer?.setVolume(0f, 0f)
      mediaPlayer?.isLooping = true//循环播放
      play()
    }
    //启用前台服务，提升优先级
    if (KeepLive.foregroundNotification != null) {
      val intent2 = Intent(applicationContext, NotificationClickReceiver::class.java)
      intent2.action = NotificationClickReceiver.CLICK_NOTIFICATION
      val notification = NotificationUtils.createNotification(this, KeepLive.foregroundNotification!!.getTitle(), KeepLive.foregroundNotification!!.getDescription(), KeepLive.foregroundNotification!!.getIconRes(), intent2)
      startForeground(13691, notification)
    }
    //绑定守护进程
    try {
      val intent3 = Intent(this, RemoteService::class.java)
      this.bindService(intent3, connection, Context.BIND_ABOVE_CLIENT)
    } catch (e: Exception) {
    }

    //隐藏服务通知
    try {
      if (Build.VERSION.SDK_INT < 25) {
        startService(Intent(this, HideForegroundService::class.java))
      }
    } catch (e: Exception) {
    }

    if (KeepLive.keepLiveService != null) {
      KeepLive.keepLiveService!!.onWorking()
    }
    return Service.START_STICKY
  }

  private fun play() {
    if (mediaPlayer != null && !mediaPlayer!!.isPlaying) {
      mediaPlayer?.start()
    }
  }

  private inner class MyBilder : GuardAidl.Stub() {

    @Throws(RemoteException::class)
    override fun wakeUp(title: String, discription: String, iconRes: Int) {

    }
  }

  private val connection = object : ServiceConnection {

    override fun onServiceDisconnected(name: ComponentName) {
      val remoteService = Intent(this@LocalService,
          RemoteService::class.java)
      this@LocalService.startService(remoteService)
      val intent = Intent(this@LocalService, RemoteService::class.java)
      this@LocalService.bindService(intent, this,
          Context.BIND_ABOVE_CLIENT)
    }

    override fun onServiceConnected(name: ComponentName, service: IBinder) {
      try {
        if (mBilder != null && KeepLive.foregroundNotification != null) {
          val guardAidl = GuardAidl.Stub.asInterface(service)
          guardAidl.wakeUp(KeepLive.foregroundNotification?.getTitle(), KeepLive.foregroundNotification?.getDescription(), KeepLive.foregroundNotification!!.getIconRes())
        }
      } catch (e: RemoteException) {
        e.printStackTrace()
      }

    }
  }

  override fun onDestroy() {
    super.onDestroy()
    unbindService(connection)
    if (KeepLive.keepLiveService != null) {
      KeepLive.keepLiveService?.onStop()
    }
  }
}

然后再定义一个远程服务，绑定本地服务。

class RemoteService : Service() {

  private var mBilder: MyBilder? = null

  override fun onCreate() {
    super.onCreate()
    if (mBilder == null) {
      mBilder = MyBilder()
    }
  }

  override fun onBind(intent: Intent): IBinder? {
    return mBilder
  }

  override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
    try {
      this.bindService(Intent(this@RemoteService, LocalService::class.java),
          connection, Context.BIND_ABOVE_CLIENT)
    } catch (e: Exception) {
    }
    return Service.START_STICKY
  }

  override fun onDestroy() {
    super.onDestroy()
    unbindService(connection)
  }

  private inner class MyBilder : GuardAidl.Stub() {
    @Throws(RemoteException::class)
    override fun wakeUp(title: String, discription: String, iconRes: Int) {
      if (Build.VERSION.SDK_INT < 25) {
        val intent = Intent(applicationContext, NotificationClickReceiver::class.java)
        intent.action = NotificationClickReceiver.CLICK_NOTIFICATION
        val notification = NotificationUtils.createNotification(this@RemoteService, title, discription, iconRes, intent)
        this@RemoteService.startForeground(13691, notification)
      }
    }
  }

  private val connection = object : ServiceConnection {
    override fun onServiceDisconnected(name: ComponentName) {
      val remoteService = Intent(this@RemoteService,
          LocalService::class.java)
      this@RemoteService.startService(remoteService)
      this@RemoteService.bindService(Intent(this@RemoteService,
          LocalService::class.java), this, Context.BIND_ABOVE_CLIENT)
    }

    override fun onServiceConnected(name: ComponentName, service: IBinder) {}
  }

}

/**
 * 通知栏点击广播接受者
 */
class NotificationClickReceiver : BroadcastReceiver() {

  companion object {
    const val CLICK_NOTIFICATION = "CLICK_NOTIFICATION"
  }

  override fun onReceive(context: Context, intent: Intent) {
    if (intent.action == NotificationClickReceiver.CLICK_NOTIFICATION) {
      if (KeepLive.foregroundNotification != null) {
        if (KeepLive.foregroundNotification!!.getForegroundNotificationClickListener() != null) {
          KeepLive.foregroundNotification!!.getForegroundNotificationClickListener()?.foregroundNotificationClick(context, intent)
        }
      }
    }
  }
}

3，JobScheduler

JobScheduler是Android从5.0增加的支持一种特殊的任务调度机制，可以用它来实现进程保活，不过在Android8.0系统中，此种方法也失效。

首先，我们定义一个JobService，开启本地服务和远程服务。

@SuppressWarnings(value = ["unchecked", "deprecation"])
@RequiresApi(Build.VERSION_CODES.LOLLIPOP)
class JobHandlerService : JobService() {

  private var mJobScheduler: JobScheduler? = null

  override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
    var startId = startId
    startService(this)
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
      mJobScheduler = getSystemService(Context.JOB_SCHEDULER_SERVICE) as JobScheduler
      val builder = JobInfo.Builder(startId++,
          ComponentName(packageName, JobHandlerService::class.java.name))
      if (Build.VERSION.SDK_INT >= 24) {
        builder.setMinimumLatency(JobInfo.DEFAULT_INITIAL_BACKOFF_MILLIS) //执行的最小延迟时间
        builder.setOverrideDeadline(JobInfo.DEFAULT_INITIAL_BACKOFF_MILLIS) //执行的最长延时时间
        builder.setMinimumLatency(JobInfo.DEFAULT_INITIAL_BACKOFF_MILLIS)
        builder.setBackoffCriteria(JobInfo.DEFAULT_INITIAL_BACKOFF_MILLIS, JobInfo.BACKOFF_POLICY_LINEAR)//线性重试方案
      } else {
        builder.setPeriodic(JobInfo.DEFAULT_INITIAL_BACKOFF_MILLIS)
      }
      builder.setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
      builder.setRequiresCharging(true) // 当插入充电器，执行该任务
      mJobScheduler?.schedule(builder.build())
    }
    return Service.START_STICKY
  }

  private fun startService(context: Context) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
      if (KeepLive.foregroundNotification != null) {
        val intent = Intent(applicationContext, NotificationClickReceiver::class.java)
        intent.action = NotificationClickReceiver.CLICK_NOTIFICATION
        val notification = NotificationUtils.createNotification(this, KeepLive.foregroundNotification!!.getTitle(), KeepLive.foregroundNotification!!.getDescription(), KeepLive.foregroundNotification!!.getIconRes(), intent)
        startForeground(13691, notification)
      }
    }
    //启动本地服务
    val localIntent = Intent(context, LocalService::class.java)
    //启动守护进程
    val guardIntent = Intent(context, RemoteService::class.java)
    startService(localIntent)
    startService(guardIntent)
  }

  override fun onStartJob(jobParameters: JobParameters): Boolean {
    if (!isServiceRunning(applicationContext, "com.xiyang51.keeplive.service.LocalService") || !isServiceRunning(applicationContext, "$packageName:remote")) {
      startService(this)
    }
    return false
  }

  override fun onStopJob(jobParameters: JobParameters): Boolean {
    if (!isServiceRunning(applicationContext, "com.xiyang51.keeplive.service.LocalService") || !isServiceRunning(applicationContext, "$packageName:remote")) {
      startService(this)
    }
    return false
  }

  private fun isServiceRunning(ctx: Context, className: String): Boolean {
    var isRunning = false
    val activityManager = ctx
        .getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager
    val servicesList = activityManager
        .getRunningServices(Integer.MAX_VALUE)
    val l = servicesList.iterator()
    while (l.hasNext()) {
      val si = l.next()
      if (className == si.service.className) {
        isRunning = true
      }
    }
    return isRunning
  }
}

4，提高Service优先级

在onStartCommand()方法中开启一个通知，提高进程的优先级。注意：从Android 8.0（API级别26）开始，所有通知必须要分配一个渠道，对于每个渠道，可以单独设置视觉和听觉行为。然后用户可以在设置中修改这些设置，根据应用程序来决定哪些通知可以显示或者隐藏。

首先，定义一个通知工具类，此工具栏兼容Android 8.0。

class NotificationUtils(context: Context) : ContextWrapper(context) {

  private var manager: NotificationManager? = null
  private var id: String = context.packageName + "51"
  private var name: String = context.packageName
  private var context: Context = context
  private var channel: NotificationChannel? = null

  companion object {
    @SuppressLint("StaticFieldLeak")
    private var notificationUtils: NotificationUtils? = null

    fun createNotification(context: Context, title: String, content: String, icon: Int, intent: Intent): Notification? {
      if (notificationUtils == null) {
        notificationUtils = NotificationUtils(context)
      }
      var notification: Notification? = null
      notification = if (Build.VERSION.SDK_INT >= 26) {
        notificationUtils?.createNotificationChannel()
        notificationUtils?.getChannelNotification(title, content, icon, intent)?.build()
      } else {
        notificationUtils?.getNotification_25(title, content, icon, intent)?.build()
      }
      return notification
    }
  }

  @RequiresApi(api = Build.VERSION_CODES.O)
  fun createNotificationChannel() {
    if (channel == null) {
      channel = NotificationChannel(id, name, NotificationManager.IMPORTANCE_MIN)
      channel?.enableLights(false)
      channel?.enableVibration(false)
      channel?.vibrationPattern = longArrayOf(0)
      channel?.setSound(null, null)
      getManager().createNotificationChannel(channel)
    }
  }

  private fun getManager(): NotificationManager {
    if (manager == null) {
      manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
    }
    return manager!!
  }

  @RequiresApi(api = Build.VERSION_CODES.O)
  fun getChannelNotification(title: String, content: String, icon: Int, intent: Intent): Notification.Builder {
    //PendingIntent.FLAG_UPDATE_CURRENT 这个类型才能传值
    val pendingIntent = PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT)
    return Notification.Builder(context, id)
        .setContentTitle(title)
        .setContentText(content)
        .setSmallIcon(icon)
        .setAutoCancel(true)
        .setContentIntent(pendingIntent)
  }

  fun getNotification_25(title: String, content: String, icon: Int, intent: Intent): NotificationCompat.Builder {
    val pendingIntent = PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT)
    return NotificationCompat.Builder(context, id)
        .setContentTitle(title)
        .setContentText(content)
        .setSmallIcon(icon)
        .setAutoCancel(true)
        .setVibrate(longArrayOf(0))
        .setSound(null)
        .setLights(0, 0, 0)
        .setContentIntent(pendingIntent)
  }
}

5，Workmanager方式

Workmanager是Android JetPac中的一个API，借助Workmanager，我们可以用它来实现应用饿保活。使用前，我们需要依赖Workmanager库，如下：

implementation "android.arch.work:work-runtime:1.0.0-alpha06"

Worker是一个抽象类，用来指定需要执行的具体任务。

public class KeepLiveWork extends Worker {
  private static final String TAG = "KeepLiveWork";

  @NonNull
  @Override
  public WorkerResult doWork() {
    Log.d(TAG, "keep-> doWork: startKeepService");
    //启动job服务
    startJobService();
    //启动相互绑定的服务
    startKeepService();
    return WorkerResult.SUCCESS;
  }
}

然后，启动keepWork方法，

  public void startKeepWork() {
    WorkManager.getInstance().cancelAllWorkByTag(TAG_KEEP_WORK);
    Log.d(TAG, "keep-> dowork startKeepWork");
    OneTimeWorkRequest oneTimeWorkRequest = new OneTimeWorkRequest.Builder(KeepLiveWork.class)
        .setBackoffCriteria(BackoffPolicy.LINEAR, 5, TimeUnit.SECONDS)
        .addTag(TAG_KEEP_WORK)
        .build();
    WorkManager.getInstance().enqueue(oneTimeWorkRequest);

  }

关于WorkManager，可以通过下面的文章来详细了解：WorkManager浅谈

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