Kotlin语言使用BroadcastReceiver示例介绍

以下是关于“Kotlin语言使用BroadcastReceiver示例介绍”的完整攻略。

什么是BroadcastReceiver？

BroadcastReceiver是一种Android组件，可以用来接收系统或应用程序发出的广播消息。广播消息是一种机制，可让应用程序在不知道其他应用程序的存在情况下相互通信。

BroadcastReceiver的注册

我们需要在AndroidManifest.xml文件中注册BroadcastReceiver，以便在系统发出广播消息时，Android系统可以找到并启动我们的BroadcastReceiver。

<receiver android:name=".MyReceiver">
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED"/>
        <action android:name="android.intent.action.PACKAGE_ADDED" />
        <action android:name="android.intent.action.PACKAGE_REMOVED" />
        <data android:scheme="package" />
    </intent-filter>
</receiver>

实现BroadcastReceiver

BroadcastReceiver是一个抽象类。我们需要创建一个继承BroadcastReceiver的子类，来实现我们自己的BroadcastReceiver。

class MyReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        when (intent.action) {
            Intent.ACTION_BOOT_COMPLETED -> {
                Log.d(TAG, "Boot completed")
            }
            Intent.ACTION_PACKAGE_ADDED -> {
                Log.d(TAG, "Package added: ${intent.data?.schemeSpecificPart}")
            }
            Intent.ACTION_PACKAGE_REMOVED -> {
                Log.d(TAG, "Package removed: ${intent.data?.schemeSpecificPart}")
            }
        }
    }

    companion object {
        const val TAG = "MyReceiver"
    }
}

上面的代码演示了如何处理三个广播消息：

• Intent.ACTION_BOOT_COMPLETED：系统启动完成
• Intent.ACTION_PACKAGE_ADDED：新的应用程序已安装
• Intent.ACTION_PACKAGE_REMOVED：应用程序已被卸载

注册Receiver并监听广播

class MainActivity : AppCompatActivity() {

    private lateinit var myReceiver: MyReceiver

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

        myReceiver = MyReceiver()

        val filter = IntentFilter().apply {
            addAction(Intent.ACTION_BOOT_COMPLETED)
            addAction(Intent.ACTION_PACKAGE_ADDED)
            addAction(Intent.ACTION_PACKAGE_REMOVED)
            addDataScheme("package")
        }

        registerReceiver(myReceiver, filter)
    }

    override fun onDestroy() {
        super.onDestroy()
        unregisterReceiver(myReceiver)
    }
}

上面的代码演示了如何在Activity中注册BroadcastReceiver，并监听特定的广播消息。

示例1：监听连接和断开网络

class NetworkReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        val connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
        val networkInfo = connectivityManager.activeNetworkInfo
        if (networkInfo?.isConnected == true) {
            Log.i(TAG, "Network connected")
            // TODO: Do something when network is connected
        } else {
            Log.i(TAG, "Network disconnected")
            // TODO: Do something when network is disconnected
        }
    }

    companion object {
        const val TAG = "NetworkReceiver"
    }
}

我们可以根据onReceive()方法的参数intent来检查广播消息的类型和内容。上面的示例演示了如何检查网络连接是否已更新。

class MainActivity : AppCompatActivity() {

    private lateinit var networkReceiver: NetworkReceiver

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

        networkReceiver = NetworkReceiver()

        val filter = IntentFilter().apply {
            addAction(ConnectivityManager.CONNECTIVITY_ACTION)
        }

        registerReceiver(networkReceiver, filter)
    }

    override fun onDestroy() {
        super.onDestroy()
        unregisterReceiver(networkReceiver)
    }
}

在Activity中注册NetworkReceiver，并监听android.net.conn.CONNECTIVITY_CHANGE广播消息。这将告诉我们Android系统是否连接了或断开了网络。

示例2：监听电池状态

class BatteryReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        when (intent.action) {
            Intent.ACTION_BATTERY_CHANGED -> {
                val level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1)
                val scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1)
                val percentage = level * 100 / scale.toFloat()
                Log.i(TAG, "Battery percentage: $percentage%")
                // TODO: Do something when battery percentage changes
            }
            Intent.ACTION_BATTERY_LOW -> {
                Log.i(TAG, "Battery is low")
                // TODO: Do something when battery is low
            }
            Intent.ACTION_BATTERY_OKAY -> {
                Log.i(TAG, "Battery is okay")
                // TODO: Do something when battery is okay
            }
        }
    }

    companion object {
        const val TAG = "BatteryReceiver"
    }
}

上面的示例演示了如何检查电池状态的变化。

class MainActivity : AppCompatActivity() {

    private lateinit var batteryReceiver: BatteryReceiver

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

        batteryReceiver = BatteryReceiver()

        val filter = IntentFilter().apply {
            addAction(Intent.ACTION_BATTERY_CHANGED)
            addAction(Intent.ACTION_BATTERY_LOW)
            addAction(Intent.ACTION_BATTERY_OKAY)
        }

        registerReceiver(batteryReceiver, filter)
    }

    override fun onDestroy() {
        super.onDestroy()
        unregisterReceiver(batteryReceiver)
    }
}

在Activity中注册BatteryReceiver，并监听Intent.ACTION_BATTERY_CHANGED、Intent.ACTION_BATTERY_LOW和Intent.ACTION_BATTERY_OKAY广播消息。这将告诉我们Android系统是否已连接电源或电池电量是否已降低。