应用程序关闭时，带有广播接收器的工作管理器不起作用

Question

我只想保持蓝牙打开，为此我会监听蓝牙状态，如果它关闭，广播接收器可以启用它。我希望它在应用程序关闭时运行。因此，即使在应用程序关闭后（当它不工作时），我也试图运行蓝牙 广播接收r。为此，我了解到我需要使用 Work Manager 来支持所有设备。我试图结合广播接收器和工作管理器。但是当应用程序关闭时我无法让它运行。

这是我的 MainActivity.java 在这里我将工作​​请求排入队列。

package com.example.workmanagersample;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import androidx.work.OneTimeWorkRequest;
import androidx.work.WorkManager;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final OneTimeWorkRequest workRequest = new OneTimeWorkRequest.Builder(MyWorker.class).build();
        WorkManager.getInstance().enqueue(workRequest);

    }
}

下面的类是我的MyWorker.java在这里我注册了receiver。

package com.example.workmanagersample;

import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.bluetooth.BluetoothAdapter;
import android.content.Context;
import android.content.IntentFilter;
import android.support.annotation.NonNull;
import android.support.v4.app.NotificationCompat;
import androidx.work.Worker;
import androidx.work.WorkerParameters;


public class MyWorker extends Worker {
    private BlueToothBroadcastReceiver myReceiver;

    public MyWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
        super(context, workerParams);
    }

    /*
     * This method is responsible for doing the work
     * so whatever work that is needed to be performed
     * we will put it here
     *
     * For example, here I am calling the method displayNotification()
     * It will display a notification
     * So that we will understand the work is executed
     * */

    @NonNull
    @Override
    public Result doWork() {
        displayNotification("My Worker", "Hey I finished my work");


        setReceiver();

        return Worker.Result.success();
    }

    /*
     * The method is doing nothing but only generating
     * a simple notification
     * If you are confused about it
     * you should check the Android Notification Tutorial
     * */
    private void displayNotification(String title, String task) {
        NotificationManager notificationManager = (NotificationManager) getApplicationContext().getSystemService(Context.NOTIFICATION_SERVICE);

        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel("simplifiedcoding", "simplifiedcoding", NotificationManager.IMPORTANCE_DEFAULT);
            notificationManager.createNotificationChannel(channel);
        }

        NotificationCompat.Builder notification = new NotificationCompat.Builder(getApplicationContext(), "simplifiedcoding")
                .setContentTitle(title)
                .setContentText(task)
                .setSmallIcon(R.mipmap.ic_launcher);

        notificationManager.notify(1, notification.build());
    }


    private void setReceiver() {
        myReceiver = new BlueToothBroadcastReceiver();
        IntentFilter filter = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);
        getApplicationContext().registerReceiver(myReceiver, filter);

    }
}

下面的类是我的 BlueToothBroadcastReceiver.java 在这里我听蓝牙状态是否改变，如果它关闭，我尝试打开它。应用程序运行时它正在工作。但是如果应用程序关闭但我无法实现它，我希望它也能工作。

package com.example.workmanagersample;

import android.bluetooth.BluetoothAdapter;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class BlueToothBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();

        if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {
            final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,
                    BluetoothAdapter.ERROR);
            switch (state) {
                case BluetoothAdapter.STATE_OFF:
                    setBluetooth(true);
                    // Bluetooth has been turned off;
                    break;
                case BluetoothAdapter.STATE_TURNING_OFF:
                    setBluetooth(true);
                    // Bluetooth is turning off;
                    break;
                case BluetoothAdapter.STATE_ON:
                    // Bluetooth has been on
                    break;
                case BluetoothAdapter.STATE_DISCONNECTING:
                    setBluetooth(true);
                    // Bluetooth is turning on
                    break;

                case BluetoothAdapter.STATE_DISCONNECTED:
                    setBluetooth(true);
                    // Bluetooth is turning on
                    break;
            }
        }
    }

    public static boolean setBluetooth(boolean enable) {
        BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        boolean isEnabled = bluetoothAdapter.isEnabled();
        if (enable && !isEnabled) {
            return bluetoothAdapter.enable();
        }
        else if(!enable && isEnabled) {
            return bluetoothAdapter.disable();
        }
        // No need to change bluetooth state
        return true;
    }
}

最后是我的 Manifest 文件；

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

    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />

    <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">
        <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:name=".BlueToothBroadcastReceiver"
            android:enabled="true">
            <intent-filter>
                <action android:name="android.bluetooth.adapter.action.STATE_CHANGED"/>
                <action android:name="android.bluetooth.adapter.action.STATE_OFF"/>
                <action android:name="android.bluetooth.adapter.action.STATE_TURNING_OFF"/>
                <action android:name="android.bluetooth.adapter.action.STATE_ON"/>
                <action android:name="android.bluetooth.adapter.action.STATE_DISCONNECTING"/>
                <action android:name="android.bluetooth.adapter.action.STATE_DISCONNECTED"/>
            </intent-filter>
        </receiver>
    </application>

</manifest>

我在周末研究后选择使用工作管理器，但当我关闭应用程序时它不起作用。我有什么遗漏或有任何限制吗？如果是这样，我该如何解决？任何帮助将非常感激！谢谢！

Answer 1

WorkManager 旨在执行任务，即使您的应用程序在后台。您可以为您的 Worker 类分配一些约束，以便它们仅在满足这些约束时执行（即，如果您需要将一些数据上传到服务器，则 WiFi 连接上的约束可用）。

这是 WorkManager 使用广播接收器（最高 API 级别 22）或 JobScheduler 的原因：了解这些约束何时发生变化。

正如其他人回答的那样，您需要使用服务（如果您需要长时间运行，前台服务可能是一个好主意）。 您应该评估的几件事：

1. 首先检查前台服务的场景。 Consider this blog post
2. 然后是documentation on foreground services。
3. 最后是Bluetooth overview。

Answer 2

您需要在应用程序关闭后保持广播接收器运行，您将 通过服务类实现这一点，您可能希望查看this 答案

Answer 3

背景

现在开始实施，您似乎有一些提示，因为我看到您有待处理的通知。因为这部分非常接近解决方案。所以实际上你必须使用前台Service（不仅仅是这里提到的Service，因为它可能会被系统终止）。

最后，我相信你有运行这个应用程序的用例。因为它对用户来说可能非常耗电，而且您知道自己在做什么。

解决方案

实现前台Service 并从应用程序启动它。确保您有内部通知。以及您对 Receiver 订阅的实现。

class LiveBroadcast : Service() {

    private var myReceiver: BlueToothBroadcastReceiver? = null

    override fun onCreate() {

        // Init Forgeround Notification
        val pendingIntent: PendingIntent =
            Intent(this, ExampleActivity::class.java).let { notificationIntent ->
                PendingIntent.getActivity(this, 0, notificationIntent, 0)
            }

        val notification: Notification = Notification.Builder(this, CHANNEL_DEFAULT_IMPORTANCE)
                .setContentTitle(getText(R.string.notification_title))
                .setContentText(getText(R.string.notification_message))
                .setSmallIcon(R.drawable.icon)
                .setContentIntent(pendingIntent)
                .setTicker(getText(R.string.ticker_text))
                .build()

        // Notification ID cannot be 0.
        startForeground(ONGOING_NOTIFICATION_ID, notification)

        // Start your BluetoothReceiver
        myReceiver = new BlueToothBroadcastReceiver()
        getApplicationContext().registerReceiver(
            myReceiver, IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));
    }

    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
        return START_STICKY
    }

    override fun onBind(intent: Intent): IBinder? {
        // Pass
    }

    override fun onDestroy() {
        // Pass
    }
}