在ImageSpan中可以使用Xamarin.Forms吗？

Question

我试图在Xamarin.Forms.Labs中调整Xamarin.Forms.Labs中的ImageButtons，以图像和文本为中心(作为块)在图像按钮上呈现ImageButtons，而不是像渲染器的默认行为那样使图像对齐到按钮的左/右边缘。

我遇到了一个StackOverflow文章，它说这种布局可以在安卓中使用ImageSpan实现--但是，当我将代码翻译到Xamarin.Forms C#时，就会显示文本，而不是图像。有人能看出这个代码有什么明显的问题吗？

源是ImageButton控件的ImageSource值。

var handler = new FileImageSourceHandler();

var bitmap = await handler.LoadImageAsync(source, this.Context);

if (bitmap != null)
{
    var bitmapWidth = this.ImageButton.ImageWidthRequest.Equals(0) ? bitmap.Width : (int)(this.ImageButton.ImageWidthRequest);
    var bitmapHeight = this.ImageButton.ImageHeightRequest.Equals(0) ? bitmap.Height : (int)(this.ImageButton.ImageHeightRequest);

    Drawable drawable = new BitmapDrawable(Resources, bitmap);
    var scaledDrawable = new ScaleDrawable(drawable, 0, bitmapWidth, bitmapHeight).Drawable;
    scaledDrawable.SetBounds(0, 0, bitmapWidth, bitmapHeight);

    var scaledBitmap = Bitmap.CreateScaledBitmap(bitmap, bitmapWidth, bitmapHeight, true);

    var leftPadding = (int)this.ImageButton.ButtonPadding.Left;
    var rightPadding = (int)this.ImageButton.ButtonPadding.Right;
    var topPadding = (int)this.ImageButton.ButtonPadding.Top;
    var bottomPadding = (int)this.ImageButton.ButtonPadding.Bottom;

    Control.SetPadding(leftPadding, topPadding, rightPadding, bottomPadding);
    Control.Gravity = GravityFlags.CenterHorizontal | GravityFlags.CenterVertical;

    switch (this.ImageButton.Orientation)
    {
        case ImageOrientation.ImageToRight:
            var rightButtonLabel = new SpannableString(string.Format("{0} ", this.Control.Text));
            //rightButtonLabel.SetSpan(new ImageSpan(scaledBitmap), rightButtonLabel.Length() - 1, rightButtonLabel.Length(), SpanTypes.InclusiveInclusive);
            //rightButtonLabel.SetSpan(new ImageSpan(scaledDrawable, SpanAlign.Bottom), rightButtonLabel.Length() - 1, rightButtonLabel.Length(), SpanTypes.InclusiveInclusive);
            //rightButtonLabel.SetSpan(new ImageSpan(scaledDrawable), rightButtonLabel.Length() - 1, rightButtonLabel.Length(), SpanTypes.InclusiveInclusive);
            rightButtonLabel.SetSpan(new ImageSpan(Forms.Context, scaledBitmap, SpanAlign.Bottom), rightButtonLabel.Length() - 1, rightButtonLabel.Length(), SpanTypes.InclusiveInclusive);
            Control.SetText(rightButtonLabel, Android.Widget.TextView.BufferType.Spannable);
            break;

        case ImageOrientation.ImageToLeft:
        default:
            var leftButtonLabel = new SpannableString(string.Format(" {0}", this.Control.Text));
            //leftButtonLabel.SetSpan(new ImageSpan(scaledBitmap), 0, 1, SpanTypes.InclusiveInclusive);
            //leftButtonLabel.SetSpan(new ImageSpan(scaledDrawable, SpanAlign.Bottom), 0, 1, SpanTypes.InclusiveInclusive);
            //leftButtonLabel.SetSpan(new ImageSpan(scaledDrawable), 0, 1, SpanTypes.ExclusiveExclusive);
            leftButtonLabel.SetSpan(new ImageSpan(Forms.Context, scaledBitmap, SpanAlign.Bottom), 0, 1, SpanTypes.InclusiveInclusive);
            Control.SetText(leftButtonLabel, Android.Widget.TextView.BufferType.Spannable);
            break;
    }
}

文字中心很好，但没有图像。我尝试了几个不同的ImageSpan重载，使用可绘制的位图，使用Forms.Context，但它们都没有工作。

在Xamarin.Forms?中使用ImageSpan是否存在一些限制？

Answer 1

是的，这是一个古老的问题。不管怎样，我想这帖子可以帮助解决这个问题。

只需将图像加载到某个(不可见的)视图中，ImageSpan图像就会显示出来。