《第一行代碼》5章 動態註冊監聽網絡變化

注意：

1. 需要在配置文件中 增加訪問網絡的權限
   

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

2. 主要就是重寫onReceiver();首先需要註冊

3. 增加幾個新類：BroadcastReceiver，
   

   package com.example.broadcasttest;
   
   import android.app.Activity;
   import android.content.BroadcastReceiver;
   import android.content.Context;
   import android.content.Intent;
   import android.content.IntentFilter;
   import android.net.ConnectivityManager;
   import android.net.NetworkInfo;
   import android.os.Bundle;
   import android.widget.TextView;
   import android.widget.Toast;
   
   public class MainActivity extends Activity {
       private IntentFilter intentFilter;
       private NetworkChangeReceiver networkChangeReceiver;
       private TextView textView;
       @Override
       protected void onCreate(Bundle savedInstanceState){
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           
           intentFilter = new IntentFilter();
           intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
           networkChangeReceiver = new NetworkChangeReceiver();
           registerReceiver(networkChangeReceiver,intentFilter);//註冊廣播接收器，接收CONNECTIVITY_CHANGE這個廣播
           textView=(TextView) findViewById(R.id.tv);
       }
       @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_LONG).show();
               //Log.d("demo","networkchanges");
           //    textView.setText("netWorkChanges");
               ConnectivityManager connectionManager=(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);//
               NetworkInfo networkInfo=connectionManager.getActiveNetworkInfo();
               if (networkInfo != null && networkInfo.isAvailable()){
                   Toast.makeText(context, "network is available", Toast.LENGTH_LONG).show();
               }else {
                   Toast.makeText(context, "network is unavailable", Toast.LENGTH_SHORT).show();
               }
               
           }
       }
   
   }