OnDraw：畫布未繪制位圖

Question

我正在使用Xamarin.Android進行自定義視圖，我想在畫布上繪制一個圓圈，然后在其上繪制一個位圖。 圓已正確繪制，但位圖未繪制。位圖對應於png圖像資源。 這是我的OnDraw

    protected async override void OnDraw(Canvas canvas)
    {
        base.OnDraw(canvas);
        Paint buttonBackgroundPaint = new Paint(PaintFlags.AntiAlias);
        Color? c = null;
        bool colorOk = Resources.TryGetColor(_backgroundColor, out c);

        buttonBackgroundPaint.Color = (Color)(colorOk ? c : _context?.Resources.GetColor(AndroidRes.Resource.Color.Black));
        canvas.DrawCircle(Width / 2, Height / 2, _radius, buttonBackgroundPaint);

        Paint bitmapPaint = new Paint(PaintFlags.AntiAlias);
        Bitmap bitmapContent = await BitmapFactory.DecodeResourceAsync(_context?.Resources, _drawableContent);
        canvas.DrawBitmap(bitmapContent, 0, 0, bitmapPaint);

    }

編輯：Resources.TryGetColor是我創建的擴展方法。

Answer 1

我注意到旋轉屏幕時會顯示位圖的一部分。 問題出在位圖范圍之內，所以我按以下方式解決了它：

protected async override void OnDraw(Canvas canvas)
{
    base.OnDraw(canvas);
    Paint buttonBackgroundPaint = new Paint(PaintFlags.AntiAlias);
    Color? c = null;
    bool colorOk = Resources.TryGetColor(_backgroundColor, out c);

    buttonBackgroundPaint.Color = (Color)(colorOk ? c : _context?.Resources.GetColor(AndroidRes.Resource.Color.Black));
    canvas.DrawCircle(Width / 2, Height / 2, _radius, buttonBackgroundPaint);

    Drawable dr = _context.Resources.GetDrawable(Resource.Drawable.image);
    dr.SetBounds(0, 0, right, bottom); // appropiate values for my case
    dr.Draw(canvas);
}