Android应用中怎么对网络连接状态进行监听

/** 
 * 
 * @author cj 判断网络工具类 
 * 
 */ 
public class NetUtil { 
  /** 
   * 没有连接网络 
   */ 
  private static final int NETWORK_NONE = -1; 
  /** 
   * 移动网络 
   */ 
  private static final int NETWORK_MOBILE = 0; 
  /** 
   * 无线网络 
   */ 
  private static final int NETWORK_WIFI = 1; 
  public static int getNetWorkState(Context context) { 
    // 得到连接管理器对象 
    ConnectivityManager connectivityManager = (ConnectivityManager) context 
        .getSystemService(Context.CONNECTIVITY_SERVICE); 
    NetworkInfo activeNetworkInfo = connectivityManager 
        .getActiveNetworkInfo(); 
    if (activeNetworkInfo != null && activeNetworkInfo.isConnected()) { 
      if (activeNetworkInfo.getType() == (ConnectivityManager.TYPE_WIFI)) { 
        return NETWORK_WIFI; 
      } else if (activeNetworkInfo.getType() == (ConnectivityManager.TYPE_MOBILE)) { 
        return NETWORK_MOBILE; 
      } 
    } else { 
      return NETWORK_NONE; 
    } 
    return NETWORK_NONE; 
  } 
} 
/** 
 * 自定义检查手机网络状态是否切换的广播接受器 
 * 
 * @author cj 
 * 
 */ 
public class NetBroadcastReceiver extends BroadcastReceiver { 
  public NetEvevt evevt = BaseActivity.evevt; 
  @Override 
  public void onReceive(Context context, Intent intent) { 
    // TODO Auto-generated method stub 
    // 如果相等的话就说明网络状态发生了变化 
    if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) { 
      int netWorkState = NetUtil.getNetWorkState(context); 
      // 接口回调传过去状态的类型 
      evevt.onNetChange(netWorkState); 
    } 
  } 
  // 自定义接口 
  public interface NetEvevt { 
    public void onNetChange(int netMobile); 
  } 
} 

<receiver android:name="cn.broadcastreceiver.NetBroadcastReceiver" > 
      <intent-filter> 
        <action android:name="android.net.conn.CONNECTIVITY_CHANGE" /> 
      </intent-filter> 
    </receiver> 
abstract public class BaseActivity extends FragmentActivity implements NetEvevt { 
  public static NetEvevt evevt; 
  /** 
   * 网络类型 
   */ 
  private int netMobile; 
  @Override 
  protected void onCreate(Bundle arg0) { 
    // TODO Auto-generated method stub 
    super.onCreate(arg0); 
    evevt = this; 
    inspectNet(); 
  } 
  /** 
   * 初始化时判断有没有网络 
   */ 
  public boolean inspectNet() { 
    this.netMobile = NetUtil.getNetWorkState(BaseActivity.this); 
    return isNetConnect(); 
    // if (netMobile == 1) { 
    // System.out.println("inspectNet：连接wifi"); 
    // } else if (netMobile == 0) { 
    // System.out.println("inspectNet:连接移动数据"); 
    // } else if (netMobile == -1) { 
    // System.out.println("inspectNet:当前没有网络"); 
    // 
    // } 
  } 
  /** 
   * 网络变化之后的类型 
   */ 
  @Override 
  public void onNetChange(int netMobile) { 
    // TODO Auto-generated method stub 
    this.netMobile = netMobile; 
    isNetConnect(); 
  } 
  /** 
   * 判断有无网络 。 
   * 
   * @return true 有网, false 没有网络. 
   */ 
  public boolean isNetConnect() { 
    if (netMobile == 1) { 
      return true; 
    } else if (netMobile == 0) { 
      return true; 
    } else if (netMobile == -1) { 
      return false; 
    } 
    return false; 
  } 
} 
public class MainActivity extends BaseActivity { 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    } 
@Override 
  public void onNetChange(int netMobile) { 
    // TODO Auto-generated method stub 
    //在这个判断，根据需要做处理 
  } 
}