Android 7.0 隐式广播-监听网络变化

Android7.0前，Android系统前网络切换时，会发广播，业务只要监听广播即可。

public class NetChangeReceiver extends BroadcastReceiver {

    private static final String ANDROID_NET_CHANGE_ACTION = "android.net.conn.CONNECTIVITY_CHANGE";

    @Override
    public void onReceive(Context context, Intent intent) {
        if(intent.getAction().equalsIgnoreCase(ANDROID_NET_CHANGE_ACTION)){
            Toast.makeText(context, "Net Changed", Toast.LENGTH_SHORT).show();
        }
    }
}

清单文件中

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.outman.example.androidtest">

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>

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

        <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=".NetChangeReceiver">
            <intent-filter >
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
            intent-filter>
        receiver>
    application>

manifest>

上面代码，在Android7.0设备前，当网络切换时，能收到消息。而在Android7.0及以上设备，则无法收到。

Android7.0 行为变更上明确说明

• Android 7.0 移除了三项隐式广播，因为隐式广播会在后台频繁启动已注册侦听这些广播的应用。删除这些广播可以显著提升设备性能和用户体验。
  为缓解这些问题，
• Android 7.0 应用了以下优化措施：
  
  • 面向 Android 7.0 开发的应用不会收到 CONNECTIVITY_ACTION 广播，即使它们已有清单条目来请求接受这些事件的通知。在前台运行的应用如果使用 BroadcastReceiver 请求接收通知，则仍可以在主线程中侦听 CONNECTIVITY_CHANGE。应用无法发送或接收 ACTION_NEW_PICTURE 或 ACTION_NEW_VIDEO 广播。此项优化会影响所有应用，而不仅仅是面向 Android 7.0 的应用。

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解决办法

在android 中注册广播有两种方式，一种是在AndroidManifest.xml中，另一种通过register方法。

Android文档中描述，通过在AndroidManifest.xml中注册方式，App在前后台都无法接收到广播。而通过register的方式，当App在运行时，是可以接收到广播

public class MainActivity extends Activity {

    private NetChangeReceiver netChangeReceiver;

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

        netChangeReceiver = new NetChangeReceiver();
        registerReceiver(netChangeReceiver, new IntentFilter("android.net.conn.CONNECTIVITY_CHANGE"));
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(netChangeReceiver);
    }
}

优化稳定建议

public class MainActivity extends Activity {

    private ConnectivityManager.NetworkCallback networkCallback;
    private ConnectivityManager connectivityManager;

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

        networkCallback = new NetworkCallbackImpl();
        NetworkRequest.Builder builder = new NetworkRequest.Builder();
        NetworkRequest request = builder.build();
        connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        connectivityManager.registerNetworkCallback(request, networkCallback);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        connectivityManager.unregisterNetworkCallback(networkCallback);
    }

    private class NetworkCallbackImpl extends ConnectivityManager.NetworkCallback {
        @Override
        public void onAvailable(Network network) {
            super.onAvailable(network);
            Toast.makeText(getBaseContext(), "onAvailable", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onLosing(Network network, int maxMsToLive) {
            super.onLosing(network, maxMsToLive);
            Toast.makeText(getBaseContext(), "onLosing", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onLost(Network network) {
            super.onLost(network);
            Toast.makeText(getBaseContext(), "onLost", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onCapabilitiesChanged(Network network, NetworkCapabilities networkCapabilities) {
            super.onCapabilitiesChanged(network, networkCapabilities);
            Toast.makeText(getBaseContext(), "onCapabilitiesChanged", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onLinkPropertiesChanged(Network network, LinkProperties linkProperties) {
            super.onLinkPropertiesChanged(network, linkProperties);
            Toast.makeText(getBaseContext(), "onLinkPropertiesChanged", Toast.LENGTH_SHORT).show();
        }
    }
}

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说明

ConnectivityManager提供了很多接口用于获取系统当前的网络连接信息：

    getAllNetworkInfo(): 返回所有网络信息
    getActiveNetworkInfo():获取当前激活的网络连接信息
    getNetworkForType: 获取指定类型的网络
    requestNetwork(...) : 请求建立某种类型的网络
    setAirplaneMode(): 开启飞行模式
    addDefaultNetworkActiveListener() : 监听默认网络连接是否激活
    registerNetworkCallback() : 监听某个网络请求的状态，可用时进行回调