安卓广播机制

标准广播

有序广播

接收系统广播

1.动态注册监听网络变化

public class MainActivity extends Activity
{  private IntentFilter intentFilter;
    private NetworkChangeReceiver networkChangeReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
//实例化意图过滤器
intentFilter=new IntentFilter("android.net.conn.CONNECTIVITY_CHANGE");
//实例化广播接收器
networkChangeReceiver=new NetworkChangeReceiver();
//注册绑定
registerReceiver(networkChangeReceiver,intentFilter);
    }
@Override
protected void onDestroy()
{
// TODO: Implement this method
super.onDestroy();
//解绑
unregisterReceiver(networkChangeReceiver);
}
class NetworkChangeReceiver extends BroadcastReceiver
{
@Override
public void onReceive(Context context, Intent intent)
{
// TODO: Implement this method
Toast.makeText(context,"网络变化",Toast.LENGTH_SHORT).show();
}
}
}

进一步优化

@Override
  public void onReceive(Context context, Intent intent)
  {
  // 找到系统管理网络服务类
  ConnectivityManager connectivityManager=(ConnectivityManager)getSystemService(context.CONNECTIVITY_SERVICE);
  //得到网络信息实例
  NetworkInfo networkInfo=connectivityManager.getActiveNetworkInfo();
  if(networkInfo!=null&&networkInfo.isAvailable()){
    Toast.makeText(context,"网络可联通",Toast.LENGTH_SHORT).show();
  }else{
    Toast.makeText(context,"无网络",Toast.LENGTH_SHORT).show();
  }
  }

记得添加权限哦