Question

我正在构建一个简单的应用程序，它会持续监控媒体级别，并将其调整为最高级别的20％，如果用户增加，则应该再次回到20％。

我遵循的概念是通过服务进行监控过程，一旦该服务被破坏，它就会调用广播接收器，广播接收器又会再次调用接收器，依此类推，作为无限循环，但看起来有些不对劲下面的代码，soit没有按预期工作，服务/广播不会一直呼叫对方！

我开始mainActivity作为：

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val audio = this.getSystemService(Context.AUDIO_SERVICE) as AudioManager
        val level = audio.getStreamVolume(AudioManager.STREAM_MUSIC)

        val maxVolume = audio.getStreamMaxVolume(AudioManager.STREAM_MUSIC)
        val percent = 0.2f
        val twintyVolume = (maxVolume * percent).toInt()

        if ( level > twintyVolume) {
            Toast.makeText(this,"audio level is $level", Toast.LENGTH_LONG).show()
            audio.setStreamVolume(AudioManager.STREAM_MUSIC,twintyVolume,0)
        }

        this.startService(Intent(this, VolumeCheck::class.java))
    }
}

以上进行初步检查并将媒体音量减小到最大音量的20％，然后启动服务，这与下面的代码相同：

class VolumeCheck : Service() {

    private lateinit var context: Context

    override fun onCreate() {
        super.onCreate()
        context = this
        Toast.makeText(this, "service created", Toast.LENGTH_SHORT).show();
    }

    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
        super.onStartCommand(intent, flags, startId)
        Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();

        val audio = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
        val mediaPlayer = MediaPlayer()


     //   Thread().run {
            val maxVolume = audio.getStreamMaxVolume(AudioManager.STREAM_MUSIC)
            val percent = 0.2f
            val twintyVolume = (maxVolume * percent).toInt()
            if (mediaPlayer.isPlaying) {
                val level = audio.getStreamVolume(AudioManager.STREAM_MUSIC)
                if ( level > twintyVolume) {
                    Toast.makeText(context,"audio level is $level", Toast.LENGTH_LONG).show()
                    audio.setStreamVolume(AudioManager.STREAM_MUSIC,twintyVolume,0)
                }
            }
      //      Thread.sleep(3000)
     //   }
        stopSelf()
        return Service.START_STICKY
    }

    override fun onBind(intent: Intent): IBinder? {
        //TODO for communication return IBinder implementation
        return null
    }

    override fun onDestroy() {
        super.onDestroy()
        Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show()
        val intent = Intent("com.kortex.mediafix.BootUpReceiver")
        sendBroadcast(intent)
    }
}

一旦服务被销毁，它就会调用引导广播接收器，然后再接收服务：

class BootUpReceiver: BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        context.startService(Intent(context, VolumeCheck::class.java))
    }
}

Manifest是：

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

    <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">
        <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=".BootUpReceiver"
            android:permission="android.permission.RECEIVE_BOOT_COMPLETED">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
                <action android:name="android.intent.action.QUICKBOOT_POWERON" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </receiver>
        <service android:name=".VolumeCheck" />
    </application>

</manifest>

Answer 1

val intent = Intent("com.kortex.mediafix.BootUpReceiver")

此行不会调用您的广播接收器，而是使用意图操作制作意图＆＃34; com.kortex.mediafix.BootUpReceiver＆＃34;

更改清单中的BootUpReceiver条目以接收此操作

<receiver android:name=".BootUpReceiver"
        android:permission="android.permission.RECEIVE_BOOT_COMPLETED">
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED" />
            <action android:name="android.intent.action.QUICKBOOT_POWERON" />
            <action android:name="com.kortex.mediafix.BootUpReceiver" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </receiver>

Answer 2

我使用从ContentObserver调用的service解决了这个问题，所以我的代码现在是：

MainActivity启动应用，并进行首次调整，然后启动服务：

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    val audio = this.getSystemService(Context.AUDIO_SERVICE) as AudioManager
    val level = audio.getStreamVolume(AudioManager.STREAM_MUSIC)

    val maxVolume = audio.getStreamMaxVolume(AudioManager.STREAM_MUSIC)
    val percent = 0.2f
    val twintyVolume = (maxVolume * percent).toInt()

    if ( level > twintyVolume) audio.setStreamVolume(AudioManager.STREAM_MUSIC,twintyVolume,0)

    Toast.makeText(this,"Audio level adjusted to 20% instead of $level", Toast.LENGTH_LONG).show()

    this.startService(Intent(this, VolumeCheck::class.java))

    finish()
   }
}

Broadcast每次重启设备时启动应用和服务：

class BootUpReceiver: BroadcastReceiver() {

override fun onReceive(context: Context, intent: Intent) {
    context.startService(Intent(context, VolumeCheck::class.java))
   }
}

Service注册并致电观察员：

class VolumeCheck : Service() {

private lateinit var context: Context
private lateinit var myObserver: VolumeOnserver


override fun onCreate() {
    super.onCreate()
    context = this
    // Define the VolumeOnserver
    myObserver = VolumeOnserver(context, Handler())
    Toast.makeText(this, "service created", Toast.LENGTH_SHORT).show();
}

override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
    super.onStartCommand(intent, flags, startId)
    Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();

    // Register the VolumeOnserver for setting changes
    contentResolver.registerContentObserver(android.provider.Settings.System.CONTENT_URI ,true, myObserver);

    return Service.START_STICKY
}

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

override fun onDestroy() {
    super.onDestroy()

    // Unregister the VolumeOnserver
    contentResolver.unregisterContentObserver(myObserver);
   }
}

Observer观察settings中的任何更改并检查媒体音量并根据需要进行调整：

class VolumeOnserver (context: Context, h: Handler?): ContentObserver(h) {

private val context = context

override fun onChange(selfChange: Boolean) {
    onChange(selfChange, uri = null)
}

// Implement the onChange(boolean, Uri) method to take advantage of the new Uri argument.
override fun onChange(selfChange: Boolean, uri: Uri?) {
    // Handle change.
    val audio = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
    val level = audio.getStreamVolume(AudioManager.STREAM_MUSIC)

    val maxVolume = audio.getStreamMaxVolume(AudioManager.STREAM_MUSIC)
    val percent = 0.2f
    val twintyVolume = (maxVolume * percent).toInt()

    if ( level > twintyVolume) audio.setStreamVolume(AudioManager.STREAM_MUSIC,twintyVolume,0)

    // Toast.makeText(context,"audio level is $level", Toast.LENGTH_LONG).show()
   }
}

Manifest文件是：

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

    <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">
        <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=".BootUpReceiver"
            android:permission="android.permission.RECEIVE_BOOT_COMPLETED">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
                <action android:name="android.intent.action.QUICKBOOT_POWERON" />
               <action android:name="com.kortex.mediafix.BootUpReceiver" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </receiver>
        <service android:name=".VolumeCheck" />
    </application>

</manifest>

我正在运行的应用是here。

但有一个问题是它不稳定，我用户坚持要改变音量，经过多次试验后，服务和/或观察者不再工作，直到应用程序重新启动。

Answer 3

另一种方法（不Service}是从ContentObserver

致电BroadcastReceiver

BroadcastReceiver：

class BootUpReceiver：BroadcastReceiver（）{

override fun onReceive(context: Context, intent: Intent) {
    val myObserver = VolumeOnserver(context, Handler())

    // Register the VolumeOnserver for setting changes
    context.contentResolver.registerContentObserver(
            android.provider.Settings.System.CONTENT_URI ,true,
            myObserver)
   }
}

ContentObserver：

类VolumeOnserver（context：Context，h：Handler？）：ContentObserver（h）{

private val context = context

override fun onChange(selfChange: Boolean) {
    onChange(selfChange, uri = null)
}

// Implement the onChange(boolean, Uri) method to take advantage of the new Uri argument.
override fun onChange(selfChange: Boolean, uri: Uri?) {
    // Handle change.
    val audio = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
    val level = audio.getStreamVolume(AudioManager.STREAM_MUSIC)

    val maxVolume = audio.getStreamMaxVolume(AudioManager.STREAM_MUSIC)
    val percent = 0.2f
    val twintyVolume = (maxVolume * percent).toInt()

    if ( level > twintyVolume) audio.setStreamVolume(AudioManager.STREAM_MUSIC,twintyVolume,0)
    }
}

MainActivity：

类MainActivity：AppCompatActivity（）{

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    val audio = this.getSystemService(Context.AUDIO_SERVICE) as AudioManager
    val level = audio.getStreamVolume(AudioManager.STREAM_MUSIC)

    val maxVolume = audio.getStreamMaxVolume(AudioManager.STREAM_MUSIC)
    val percent = 0.2f
    val twintyVolume = (maxVolume * percent).toInt()

    if ( level > twintyVolume) audio.setStreamVolume(AudioManager.STREAM_MUSIC,twintyVolume,0)

    finish()
   }
}

继续互相呼叫服务/广播

3 个答案: