ios - 使用 MonoTouch 以编程方式绘制矩形

Question

我想了解更多有关 MonoTouch 的信息，因此我尝试使用 Quartz2D 进行绘图。我想创建一个示例，在其中以编程方式绘制 n 个矩形。问题是只绘制了第一个。我认为第二个被第一个删除/清除/覆盖。

这是我的代码:

SingleViewMTViewController.cs

public override void ViewDidLoad ()
    {
        base.ViewDidLoad ();

        PointF locationOne = new PointF (5, 5);
        PointF locationTwo = new PointF (5, 100);
        SizeF size = new SizeF (120, 40);

        DraggableRectangle tView = new DraggableRectangle (locationOne, size, UIColor.Yellow);
        DraggableRectangle tView2 = new DraggableRectangle (locationTwo, size, UIColor.Brown);

        DraggableRectangle[] views = new DraggableRectangle[2];
        views [0] = tView;
        views [1] = tView2;

        View.AddSubviews (views);
    }

DraggableRectangle.cs

public class DraggableRectangle : UIView
{
    private CGPath path;
    private PointF _targetLocation;
    private SizeF _size;
    private UIColor _fillColor = UIColor.Brown;

    public DraggableRectangle (PointF targetLocation, SizeF size)
    {
        _targetLocation = targetLocation;
        _size = size;

        RectangleF frameRect = new RectangleF (_targetLocation.X, _targetLocation.Y, _size.Width, _size.Height);
        this.Frame = frameRect;
        this.BackgroundColor = UIColor.Clear; //without this, nothing is drawn
    }

    public DraggableRectangle (PointF targetLocation, SizeF size, UIColor fillColor):this(targetLocation,size)
    {
        _fillColor = fillColor;
    }

    public override void Draw (RectangleF rect)
    {
        //base.Draw (rect);
        //works without base-call?

        //get graphics context
        using (CGContext gctx = UIGraphics.GetCurrentContext ()) {

            //set up drawing attributes
            _fillColor.SetFill ();

            //create geometry
            path = new CGPath ();

            path.AddRect (new RectangleF (_targetLocation.X, _targetLocation.Y, _size.Width, _size.Height));

            path.CloseSubpath ();

            //add geometry to graphics context and draw it
            gctx.AddPath (path);        
            gctx.DrawPath (CGPathDrawingMode.FillStroke);   
        }       
    }

有没有更好的方法来使用 MonoTouch 绘制独立的矩形？或者有人可以解释一下我做错了什么吗？

更新:顺便说一句。我能达到的最佳输出，但这对“黄色”和“棕色”来说是不正确的 http://www.bilder-upload.eu/show.php?file=81bfea-1329755225.png http://www.bilder-upload.eu/show.php?file=81bfea-1329755225.png

Answer 1

实际上，您的两个矩形都已绘制。问题是您的 _targetLocation.Y 值。您正在为 View 的 Frame 及其要在其 Draw 方法中绘制的矩形设置相同的 Y 值。

基本上，您的矩形绘制在 View 边界之外。您的“棕色” View 的高度为 40pt，而其矩形绘制在 Y=100(低于其可见部分)处。

您必须区分这些值，因为 View 的位置始终相对于其父级的坐标。

编辑:伪代码示例。

下面一行:

path.AddRect (new RectangleF (_targetLocation.X, _targetLocation.Y, _size.Width, _size.Height));

应该是这样的:

    path.AddRect (new RectangleF ({Frame.Width >= something >= 0}, 
{Frame.Height >= something >= 0}, width, height);

编辑#2:

如果我更改路径的矩形，则使用以下命令:

path.AddRect (new RectangleF (0f, 0f, _size.Width, _size.Height));

这是我得到的...