我正在尝试构建自己的“PictureBox like”控件来添加一些功能。例如,我希望能够通过简单地用鼠标单击和拖动来平移大图像。
问题似乎出在我的OnMouseMove方法上。如果我使用下面的代码,我会得到我想要的拖动速度和精度,但是当然,当我释放鼠标按钮并再次尝试拖动时,图像会恢复到原来的位置。
using System.Drawing;
using System.Windows.Forms;
namespace Testing
{
public partial class ScrollablePictureBox : UserControl
{
private Image image;
private bool centerImage;
public Image Image
{
get { return image; }
set { image = value; Invalidate(); }
}
public bool CenterImage
{
get { return centerImage; }
set { centerImage = value; Invalidate(); }
}
public ScrollablePictureBox()
{
InitializeComponent();
SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer, true);
Image = null;
AutoScroll = true;
AutoScrollMinSize = new Size(0, 0);
}
private Point clickPosition;
private Point scrollPosition;
protected override void OnMouseDown(MouseEventArgs e)
{
base.OnMouseDown(e);
clickPosition.X = e.X;
clickPosition.Y = e.Y;
}
protected override void OnMouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);
if (e.Button == MouseButtons.Left)
{
scrollPosition.X = clickPosition.X - e.X;
scrollPosition.Y = clickPosition.Y - e.Y;
AutoScrollPosition = scrollPosition;
}
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
e.Graphics.FillRectangle(new Pen(BackColor).Brush, 0, 0, e.ClipRectangle.Width, e.ClipRectangle.Height);
if (Image == null)
return;
int centeredX = AutoScrollPosition.X;
int centeredY = AutoScrollPosition.Y;
if (CenterImage)
{
//Something not relevant
}
AutoScrollMinSize = new Size(Image.Width, Image.Height);
e.Graphics.DrawImage(Image, new RectangleF(centeredX, centeredY, Image.Width, Image.Height));
}
}
}
但是,如果我将OnMouseMove方法修改为如下所示:
protected override void OnMouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);
if (e.Button == MouseButtons.Left)
{
scrollPosition.X += clickPosition.X - e.X;
scrollPosition.Y += clickPosition.Y - e.Y;
AutoScrollPosition = scrollPosition;
}
}
...你会看到拖动不像以前那样平滑,有时表现得很奇怪(比如滞后或其他东西)。
我究竟做错了什么?
我还尝试在绝望的运动中删除所有“基本”调用来解决这个问题,哈哈,但同样,它没有用。
谢谢你的时间。