Android 动态注册监听网络变化实例详解

2019-12-12 02:25:34

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Android 动态注册监听网络变化实例详解

新建一个BroadcastTest项目，然后修改MainActivity中的代码，如下：

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();      }    }  }}

动态注册的广播接收器一定要取消注册才行，在onDestroy()方法中通过调用unregisterReceiver()方法来实现。

访问系统的网络状态需要声明权限，打开AndroidManifest.xml文件，在里面加入权限，如下：

<?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>

运行程序，打开数据连接、关闭数据连接，效果如下：