android判断是不是有网络

1

public static boolean checkNet(Activity act) {                 ConnectivityManager manager = (ConnectivityManager) act                .getApplicationContext().getSystemService(                       Context.CONNECTIVITY_SERVICE);                 if (manager == null) {             return false;         }                 NetworkInfo networkinfo = manager.getActiveNetworkInfo();                 if (networkinfo == null || !networkinfo.isAvailable()) {             return false;         }            return true;      }  

?2 大同小异

public static boolean checkNet_(Context context) {		ConnectivityManager mConnectivity = (ConnectivityManager) context				.getSystemService(Context.CONNECTIVITY_SERVICE);		NetworkInfo info = mConnectivity.getActiveNetworkInfo();		if (info == null) {			return false;		}		if (!info.isAvailable() || !mConnectivity.getBackgroundDataSetting()) {			return false;		} else {			return true;		}	}

?3

private int checkNet__(Context context) {				ConnectivityManager connectionManager = (ConnectivityManager) context				.getSystemService("connectivity");		NetworkInfo networkInfo = connectionManager.getActiveNetworkInfo();		if(networkInfo != null){		if (networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {									return 1;    //返回1是 WIFI网络		} else if (networkInfo.getType() == ConnectivityManager.TYPE_MOBILE) {									return 2;    //返回 2是移动互联网（）		} else {						return 3;    //返回3是 未知网络		}		}		else{			return 0;		}	}