Paint 事件处理程序在几次迭代后停止执行
我有一个 Windows 窗体，可以循环显示以幻灯片形式显示在窗体上的图像。我这样做的方法是让一个面板控制它所在窗体的大小，并添加一个事件处理程序来绘制内存中存在的图像对象。
void panel_Paint(object sender, PaintEventArgs e)
{
if (_bShowImage)
{
Point leftCorner = new Point((this.Bounds.Width / 2) - (_image.Width / 2), (this.Bounds.Height / 2) - (_image.Height / 2));
e.Graphics.DrawImage(_image, leftCorner);
_bShowImage = false;
}
}
当加载新图像并由 _image 引用时，我强制面板重绘：
_bShowImage = true;
_panel.Refresh();
紧接着，图像被处理并从全局变量中取消引用：
_image.Dispose();
_image = null;
我已经看到它工作了一段时间，比如说 5 次迭代，那么 panel_Paint() 处理程序不会被调用。我使用 2-3 个 JPG 进行显示，我知道它们没有损坏，因为它们在前 x 次显示得很好。我在面板的 Refresh() 方法周围放置了调试线，该方法执行良好。就好像对处理程序的调用已被删除。以前有人遇到过这个问题吗？
I've got a Windows Form that circulates through images which are displayed on the form as a slideshow. The way I'm doing this is to have a Panel control the size of the form it resides in, and add an event handler that draws an Image object that exists in memory.
void panel_Paint(object sender, PaintEventArgs e)
{
if (_bShowImage)
{
Point leftCorner = new Point((this.Bounds.Width / 2) - (_image.Width / 2), (this.Bounds.Height / 2) - (_image.Height / 2));
e.Graphics.DrawImage(_image, leftCorner);
_bShowImage = false;
}
}
When a new Image is loaded and referenced by _image, I'm forcing the Panel to redraw:
_bShowImage = true;
_panel.Refresh();
Immediately afterwards, the image is disposed and the dereferenced from the global variable:
_image.Dispose();
_image = null;
I've seen that it works for a while, say 5 iterations, then the panel_Paint() handler is not being called. I'm using 2-3 JPG's for the display and I know they're not corrupted as they are shown fine for the first x times. I've put debug lines around the Refresh() method of the panel which execute fine. It's as if the call to the handler has been dropped. Has anyone encountered this problem before?
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评论（2）
这实在是太倒退了。要么像现在一样使用绘制事件处理程序。这很好（我说它比图片框更好），但是你需要删除 _bShowImage 和 _image.Dispose 东西。相反，您应该在使用新图像启动之前处理 _image。但在那之前。
或者，如果您绝对必须在绘制后立即处理 _image，那么您应该使用 Panel.CreateGraphics 来获取可用于立即绘制 _image 并删除事件的 Graphichs 对象。
就目前情况而言——这真是令人困惑。另外：.Invalidate() 是您几乎总是想要的，而不是 .Refresh()。自 VB6 时代以来，这一直是许多人的观念中的一个问题。
This is so completely backwards. Either you use a paint event handler like now. It's just fine (I say it's better than a picturebox) but then you need to drop that _bShowImage and _image.Dispose stuff. You should instead dispose the _image before you power it up with a new one. But not until that.
Or, if you absolutley must dispose the _image right after it's painted, then you should instead use Panel.CreateGraphics to get a Graphichs object you can use to immediately draw the _image and drop the event.
As it stands - it is just darn confusing. Also: .Invalidate() is what you almost always want -not .Refresh(). That's just something that got stuck in many minds since the VB6 era.
将图片放入图片框中并以这种方式循环浏览它们，这样您就不必每次都强制重新绘制整个窗口，这不是更聪明吗？
只是一个想法……
托尼
Wouldn't it be smarter to put your pictures in a picture box and loop through them in that way, so that you don't force a repaint on the whole window each time?
just a thought...
Tony