检查设备是否具有互联网连接

将所需的网络权限添加到应用程序清单文件：

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />

/**
 * If network connectivity is available, will return true
 *
 * @param context the current context
 * @return boolean true if a network connection is available
 */
public static boolean isNetworkAvailable(Context context) {
    ConnectivityManager connectivity = (ConnectivityManager) context
            .getSystemService(Context.CONNECTIVITY_SERVICE);
    if (connectivity == null) {
        Log.d("NetworkCheck", "isNetworkAvailable: No");
        return false;
    }

    // get network info for all of the data interfaces (e.g. WiFi, 3G, LTE, etc.)
    NetworkInfo[] info = connectivity.getAllNetworkInfo();

    // make sure that there is at least one interface to test against
    if (info != null) {
        // iterate through the interfaces
        for (int i = 0; i < info.length; i++) {
            // check this interface for a connected state
            if (info[i].getState() == NetworkInfo.State.CONNECTED) {
                Log.d("NetworkCheck", "isNetworkAvailable: Yes");
                return true;
            }
        }
    }
    return false;
}