Android 動態注冊監聽網絡變化實例詳解

2019-10-22 18:31:49

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Android 動態注冊監聽網絡變化實例詳解

新建一個BroadcastTest項目，然后修改MainActivity中的代碼，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");  //廣播接收器想要監聽什么廣播，就在這里添加相應的action    networkChangeReceiver=new NetworkChangeReceiver();    registerReceiver(networkChangeReceiver,intentFilter);       //調用resigerReceiver()方法進行注冊  }  @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);  //得到系統服務類      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();      }    }  }}

動態注冊的廣播接收器一定要取消注冊才行，在onDestroy()方法中通過調用unregisterReceiver()方法來實現。

訪問系統的網絡狀態需要聲明權限，打開AndroidManifest.xml文件，在里面加入權限，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>

運行程序，打開數據連接、關閉數據連接，效果如下：

Android,動態注冊監聽網絡變化,監聽網路