判断是否有网

public static boolean isNetworkAvailable(Context context) {
        ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        if (connectivity != null) {
            NetworkInfo info = connectivity.getActiveNetworkInfo();
            if (info != null && info.isConnected())
            {
                // 当前网络是连接的
                if (info.getState() == NetworkInfo.State.CONNECTED) {
                    // 当前所连接的网络可用
                    return true;
                }
            }
        }
        return false;
    }
    ```