判断当前网络是否可用

public static boolean isNetworkAvailable(Context context) {
		ConnectivityManager connm
		= (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
		if (connm == null) {
			return false;
		} else {
			NetworkInfo[] nis = connm.getAllNetworkInfo();
			if (nis != null) {
				for (int i = 0; i < nis.length; i++) {
					if (nis[i].getState() == NetworkInfo.State.CONNECTED) {
						return true;
					}
				}
			}
		}
		return false;
	}