《第一行代码》5章 动态注册监听网络变化

注意：

1. 需要在配置文件中 增加访问网络的权限
   

   
   

2. 主要就是重写onReceiver();首先需要注册

3. 增加几个新类：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);//注册广播接收器，接收CONNECTIVITY_CHANGE这个广播
   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();
   }
   
   }
   }
   
   }