将Base64图像发送到服务器，然后从服务器拉出以显示以后的Xamarin

I am new to Xamarin Andriod Development. I am trying to send a Base64 encoded image to mySQL server database and then retrieving the Base64 encoded image in the database when starting the app and displaying it. I have been able to get all the other information in the database to display, the only thing missing is the images when I open the app.

我是Xamarin Andriod Development的新手。我正在尝试将Base64编码的图像发送到mySQL服务器数据库，然后在启动应用程序并显示它时检索数据库中的Base64编码图像。我已经能够显示数据库中的所有其他信息，唯一缺少的是打开应用程序时的图像。

My code looks like this:

我的代码如下所示：

Sending the Image to the server

将图像发送到服务器

    protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
    {
        base.OnActivityResult(requestCode, resultCode, data);

        if (resultCode == Result.Ok)
        {
            int contactID = mContacts[(int)mSelectedPic.Tag].ID;

            Stream stream = ContentResolver.OpenInputStream(data.Data);
            mSelectedPic.SetImageBitmap(DecodeBitmapFromStream(data.Data, 150, 150));

            Bitmap bitmap = BitmapFactory.DecodeStream (stream);
            MemoryStream memStream = new MemoryStream ();
            bitmap.Compress (Bitmap.CompressFormat.Webp, 100, memStream);
            byte[] picData = memStream.ToArray ();

            WebClient client = new WebClient ();
            Uri uri = new Uri ("MYWESBITE/UpdateContact.php");
            NameValueCollection parameters = new NameValueCollection ();
            parameters.Add ("Image", Convert.ToBase64String(picData));
            parameters.Add ("ContactID", contactID.ToString());

            client.UploadValuesAsync (uri, parameters);
            client.UploadValuesCompleted += Client_UploadValuesCompleted;
        }

    }

PHP code to handle the image and store it into the database as a VARBINARY

用于处理映像并将其作为VARBINARY存储到数据库中的PHP代码

    $imgData = base64_encode($mImage);

    $sql = "UPDATE Contact SET ImageBase64 = '$imgData' WHERE ID = '$mContactID'";

    $result = mysql_query($sql, $link);

    if (!$result) {
        echo "DB Error, could not query the database\n";
        echo 'MySQL Error: ' . mysql_error();
        exit;
    }

Then when the app opens it calls this PHP function

然后当应用程序打开时，它会调用此PHP函数

$sql = "SELECT * FROM Contact";

$result = mysql_query($sql, $link);

if (!$result) {
    echo "DB Error, could not query the database\n";
    echo 'MySQL Error: ' . mysql_error();
    exit;
}

//create an array
$contact_array = array();
while($row =mysql_fetch_assoc($result))
{
$contact_array[] = array("ID" => $row["ID"],
                "Name" => $row["Name"],
                "Number" => $row["Number"],
                "ImageBase64" => base64_encode($row["ImageBase64"])
                );
}

echo json_encode($contact_array);

This shows how I turn the base64_encoded string to a byte array

这显示了我如何将base64_encoded字符串转换为字节数组

class Contact
{
    public int ID { get; set; }
    public string Name { get; set; }
    public string Number { get; set; }
    public string ImageBase64 { private get; set; }
    public byte [] Image
    {
        get
        {
            if (ImageBase64 != "" && ImageBase64 != null)
            {
                byte[] image = Convert.FromBase64String (ImageBase64);

                return image;

            }

            return null;

        }
    }
}

MainActivity.cs

    protected override void OnCreate(Bundle bundle)
    {

        base.OnCreate(bundle);
        SetContentView(Resource.Layout.Main);

        mListView = FindViewById<ListView>(Resource.Id.listView);
        mProgressBar = FindViewById<ProgressBar> (Resource.Id.progressBar);

        mClient = new WebClient ();
        mUrl = new Uri ("MYWEBSITE/GetContacts.php");

        //Call the Client
        mClient.DownloadDataAsync (mUrl);
        mClient.DownloadDataCompleted += MClient_DownloadDataCompleted;



    }

Then finally gets converted to image like this

然后最终转换为这样的图像

    ImageView pic = row.FindViewById<ImageView>(Resource.Id.imgPic);

    if (mContacts[position].Image != null)
    {

        pic.SetImageBitmap(BitmapFactory.DecodeByteArray(mContacts[position].Image, 0, mContacts[position].Image.Length));
    }

Thank you for your time everyone, I hope you can help me figure this out!

感谢大家的时间，我希望你能帮我解决这个问题！

2 个解决方案

#1

A few questions might help to answer this: At what point does it not work? Are you getting an error? or does the image not display?

一些问题可能有助于回答这个问题：它在什么时候不起作用？你收到错误了吗？或图像不显示？

Right off the bat, however, it looks like you are trying to interact from the UI from a background thread. Can you try wrapping the code in your MCClient_Downloaded method in RunOnUIThread?

然而，刚刚开始，看起来你正试图从后台线程的UI进行交互。您可以尝试在RunOnUIThread中的MCClient_Downloaded方法中包装代码吗？

#2

I got it to work now. I changed my database type to be a Medium BLOB instead of a VARBINARY, and then got rid of the base64_encode() on the way into the database and then got rid of the base64_encode() on the way out of the database in the JSON creation.

我现在就开始工作了。我将我的数据库类型更改为中等BLOB而不是VARBINARY，然后在进入数据库的路上删除了base64_encode（），然后在JSON创建中从数据库出来的路上删除了base64_encode（）。

#1