Android 动态注册监听网络变化实例详解

public class MainActivity extends AppCompatActivity {
  private IntentFilter intentFilter;
  private NetworkChangeReceiver networkChangeReceiver;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    intentFilter=new IntentFilter();
    intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");  //广播接收器想要监听什么广播，就在这里添加相应的action
    networkChangeReceiver=new NetworkChangeReceiver();
    registerReceiver(networkChangeReceiver,intentFilter);       //调用resigerReceiver()方法进行注册
  }

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

  class NetworkChangeReceiver extends BroadcastReceiver{
    @Override
    public void onReceive(Context context, Intent intent){
//     Toast.makeText(context,"network changes",Toast.LENGTH_SHORT).show();
      ConnectivityManager connectionManager=(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);  //得到系统服务类
      NetworkInfo networkInfo=connectionManager.getActiveNetworkInfo();
      if(networkInfo!=null&&networkInfo.isAvailable()){
        Toast.makeText(context,"network is available",Toast.LENGTH_SHORT).show();
      }else{
        Toast.makeText(context,"network is unavailable",Toast.LENGTH_SHORT).show();
      }
    }
  }
}

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

  <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/ 
  <application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    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 
  </application 

</manifest