构建永不中止运行的Android服务

时间 2019-11-07

原文原文链接

这些天我一直在努力寻找在Android中运行永不中止服务的方法。这只是追求同一目标的指南。但愿能帮助到你！php

问题

因为Android 8.0（API级别26）中引入了Android电池优化，后台服务如今有一些重要的限制。基本上，一旦应用程序处于后台运行一段时间，它们就会被杀死，这使得它们对于运行永不中止运行的服务毫无价值。根据Android的建议，咱们应该使用JobScheduler唤醒锁，在做业运行时让手机保持清醒状态它彷佛运行得很好，而且会为咱们处理唤醒锁。不幸的是，这是行不通的。最重要的是，JobScheduler打盹模式(你须要将数据发送到你的服务器)的限制列表将根据Android自行决定运行工做，一旦手机进入打盹模式，这些工做的运行频率将不断增长。甚至最糟糕的是，若是你想要访问网络 (你须要将数据发送到你的服务器)你将没法作到。查看打盹模式所施加的限制列表。若是您不介意没法访问网络而且您不关心不控制周期性，JobScheduler也能够正常工做。在咱们的例子中，咱们但愿咱们的服务以很是特定的频率运行，永远不会中止，因此咱们须要其余东西。html

关于前台服务

若是你一直在寻找解决这个问题的互联网，你极可能最终从Android的文档到达了这个页面。在那里，咱们介绍了Android提供的不一样类型的服务。看一下Foreground Service描述：java

前台服务执行一些用户能够注意到的操做。例如，音频应用程序将使用前台服务播放音频轨。前台服务必须显示通知。即便用户不与应用程序交互，前台服务也会继续运行。android

这彷佛正是咱们正在寻找的……确实如此！git

个人代码

建立一个foreground service真正是一个简单的过程，因此我将访问并解释构建永不中止的前台服务所需的全部步骤。像往常同样，我已经建立了一个包含全部代码的存储库，以防您想要查看它并跳过帖子的其他部分。添加一些依赖项github

我在这个例子中使用Kotlin协同程序Fuel，所以咱们将利用协同程序和Fuel库来处理HTTP请求。为了添加这些依赖项，咱们必须将它们添加到咱们的build.gradle文件中：shell

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.jaredrummler:android-device-names:1.1.8'

    implementation 'com.github.kittinunf.fuel:fuel:2.1.0'
    implementation 'com.github.kittinunf.fuel:fuel-android:2.1.0'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.0-M1'

    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}
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咱们的service

Foreground Services须要显示通知，以便用户知道应用程序仍在运行。若是你考虑一下，这是有道理的。请注意，咱们必须覆盖一些处理服务生命周期关键方面的Service回调方法(callback methods)。咱们使用部分唤醒锁打盹模式的也很是重要，所以咱们的服务永远不会受到打盹模式的影响。请记住，这会对咱们手机的电池寿命产生影响，所以咱们必须评估咱们的用例是否能够经过Android提供的任何其余替代方案来处理，以便在后台运行流程。代码中有一些实用函数调用（log，setServiceState）和一些自定义枚举（ServiceState.STARTED），但不要太担忧。若是您想了解它们的来源，请查看示例存储库。编程

class EndlessService : Service() {

    private var wakeLock: PowerManager.WakeLock? = null
    private var isServiceStarted = false

    override fun onBind(intent: Intent): IBinder? {
        log("Some component want to bind with the service")
        // We don't provide binding, so return null return null } override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int { log("onStartCommand executed with startId: $startId") if (intent != null) { val action = intent.action log("using an intent with action $action") when (action) { Actions.START.name -> startService() Actions.STOP.name -> stopService() else -> log("This should never happen. No action in the received intent") } } else { log( "with a null intent. It has been probably restarted by the system." ) } // by returning this we make sure the service is restarted if the system kills the service return START_STICKY } override fun onCreate() { super.onCreate() log("The service has been created".toUpperCase()) var notification = createNotification() startForeground(1, notification) } override fun onDestroy() { super.onDestroy() log("The service has been destroyed".toUpperCase()) Toast.makeText(this, "Service destroyed", Toast.LENGTH_SHORT).show() } private fun startService() { if (isServiceStarted) return log("Starting the foreground service task") Toast.makeText(this, "Service starting its task", Toast.LENGTH_SHORT).show() isServiceStarted = true setServiceState(this, ServiceState.STARTED) // we need this lock so our service gets not affected by Doze Mode wakeLock = (getSystemService(Context.POWER_SERVICE) as PowerManager).run { newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "EndlessService::lock").apply { acquire() } } // we're starting a loop in a coroutine
        GlobalScope.launch(Dispatchers.IO) {
            while (isServiceStarted) {
                launch(Dispatchers.IO) {
                    pingFakeServer()
                }
                delay(1 * 60 * 1000)
            }
            log("End of the loop for the service")
        }
    }

    private fun stopService() {
        log("Stopping the foreground service")
        Toast.makeText(this, "Service stopping", Toast.LENGTH_SHORT).show()
        try {
            wakeLock?.let {
                if (it.isHeld) {
                    it.release()
                }
            }
            stopForeground(true)
            stopSelf()
        } catch (e: Exception) {
            log("Service stopped without being started: ${e.message}")
        }
        isServiceStarted = false
        setServiceState(this, ServiceState.STOPPED)
    }

    private fun pingFakeServer() {
        val df = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.mmmZ")
        val gmtTime = df.format(Date())

        val deviceId = Settings.Secure.getString(applicationContext.contentResolver, Settings.Secure.ANDROID_ID)

        val json =
            """ { "deviceId": "$deviceId", "createdAt": "$gmtTime" } """
        try {
            Fuel.post("https://jsonplaceholder.typicode.com/posts")
                .jsonBody(json)
                .response { _, _, result ->
                    val (bytes, error) = result
                    if (bytes != null) {
                        log("[response bytes] ${String(bytes)}")
                    } else {
                        log("[response error] ${error?.message}")
                    }
                }
        } catch (e: Exception) {
            log("Error making the request: ${e.message}")
        }
    }

    private fun createNotification(): Notification {
        val notificationChannelId = "ENDLESS SERVICE CHANNEL"

        // depending on the Android API that we're dealing with we will have // to use a specific method to create the notification if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) { val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager; val channel = NotificationChannel( notificationChannelId, "Endless Service notifications channel", NotificationManager.IMPORTANCE_HIGH ).let { it.description = "Endless Service channel" it.enableLights(true) it.lightColor = Color.RED it.enableVibration(true) it.vibrationPattern = longArrayOf(100, 200, 300, 400, 500, 400, 300, 200, 400) it } notificationManager.createNotificationChannel(channel) } val pendingIntent: PendingIntent = Intent(this, MainActivity::class.java).let { notificationIntent -> PendingIntent.getActivity(this, 0, notificationIntent, 0) } val builder: Notification.Builder = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) Notification.Builder( this, notificationChannelId ) else Notification.Builder(this) return builder .setContentTitle("Endless Service") .setContentText("This is your favorite endless service working") .setContentIntent(pendingIntent) .setSmallIcon(R.mipmap.ic_launcher) .setTicker("Ticker text") .setPriority(Notification.PRIORITY_HIGH) // for under android 26 compatibility .build() } } 复制代码

是时候处理Android Manifest了json

咱们须要一些额外的权限FOREGROUND_SERVICE，INTERNET和WAKE_LOCK。请确保您不要忘记包含它们，由于它不会起做用。一旦咱们将它们放到位，咱们将须要声明服务。bash

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.robertohuertas.endless">

    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"></uses-permission>
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <uses-permission android:name="android.permission.WAKE_LOCK" />

    <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme">

        <service android:name=".EndlessService" android:enabled="true" android:exported="false">
        </service>

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>
</manifest>
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启动这项服务

根据Android版本，咱们必须使用特定方法启动服务。若是Android版本低于API 26，咱们必须使用startServicestartForegroundService。在任何其余状况下，是咱们使用startForegroundService。在这里你能够看到咱们的MainActivity，只有一个屏幕，有两个按钮来启动和中止服务。这就是您开始咱们永不中止的服务所需的一切。请记住，您能够查看此GitHub存储库中的完整代码。

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        title = "Endless Service"

        findViewById<Button>(R.id.btnStartService).let {
            it.setOnClickListener {
                log("START THE FOREGROUND SERVICE ON DEMAND")
                actionOnService(Actions.START)
            }
        }

        findViewById<Button>(R.id.btnStopService).let {
            it.setOnClickListener {
                log("STOP THE FOREGROUND SERVICE ON DEMAND")
                actionOnService(Actions.STOP)
            }
        }
    }

    private fun actionOnService(action: Actions) {
        if (getServiceState(this) == ServiceState.STOPPED &amp;&amp; action == Actions.STOP) return
        Intent(this, EndlessService::class.java).also {
            it.action = action.name
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                log("Starting the service in >=26 Mode")
                startForegroundService(it)
                return
            }
            log("Starting the service in < 26 Mode")
            startService(it)
        }
    }
}
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效果：在Android启动时启动服务

好的，咱们如今有永不中止的服务，每分钟都按照咱们的意愿发起网络请求，而后用户从新启动手机……咱们的服务不会从新开始……：(失望) 别担忧，咱们也能够为此找到解决方案。咱们将建立一个名为BroadCastReceiverStartReceiver。

class StartReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        if (intent.action == Intent.ACTION_BOOT_COMPLETED &amp;&amp; getServiceState(context) == ServiceState.STARTED) {
            Intent(context, EndlessService::class.java).also {
                it.action = Actions.START.name
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    log("Starting the service in >=26 Mode from a BroadcastReceiver")
                    context.startForegroundService(it)
                    return
                }
                log("Starting the service in < 26 Mode from a BroadcastReceiver")
                context.startService(it)
            }
        }
    }
}
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而后，咱们将再次修改咱们Android Manifest并添加一个新的权限（RECEIVE_BOOT_COMPLETED）和咱们新的BroadCastReceiver。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.robertohuertas.endless">
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"></uses-permission>
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

    <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme">

        <service android:name=".EndlessService" android:enabled="true" android:exported="false">
        </service>

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>

        <receiver android:enabled="true" android:name=".StartReceiver">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>

    </application>
</manifest>
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请注意，除非服务已在运行，不然不会从新启动该服务。这就是咱们编程的方式，并非说它必须是这样的。若是您想测试这个，只要启动一个包含谷歌服务的模拟器，并确保在root模式下运行adb。

adb root 
# If you get an error then you're not running the proper emulator.
# Be sure to stop the service
# and force a system restart:
adb shell stop 
adb shell start 
# wait for the service to be restarted!
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构建永不中止运行的Android服务

问题

关于前台服务

个人代码

咱们的service

启动这项服务

Enjoy！