Question

我正在尝试使图像的宽度缩小，更改图像源，然后再缩小。它缩小了，但它不会再增长。任何想法有什么不对？

while (pictureBox2.Size.Width > 0)
{
    int width = pictureBox2.Size.Width;
    width -= 2;
    pictureBox2.Size = new Size(width, pictureBox2.Size.Height);
    pictureBox2.Location = new Point(pictureBox2.Location.X + 1, pictureBox2.Location.Y);
    System.Threading.Thread.Sleep(1);
}
pictureBox1.Image = currentImage;
while (pictureBox2.Size.Width < 191)
{
    int width = pictureBox2.Size.Width;
    width += 2;
    pictureBox2.Size = new Size(width, pictureBox2.Size.Height);
    pictureBox2.Location = new Point(pictureBox2.Location.X - 1, pictureBox2.Location.Y);
    System.Threading.Thread.Sleep(1);
}

Answer 1

我怀疑您的绘图问题是由于不允许Windows正确绘制控件。通常，Windows控件在处理消息泵时会收到WM_PAINT或等效项。如果应用程序不处理此泵（因为他们忙于while循环休眠），则通常不会发生更新。

如果您想在while循环中执行此操作，那么您可以使用pictureBox2.Refresh()而不是调用Thread.Sleep()。前者将阻止当前线程（UI线程）并允许图片框重新绘制自己。后者仅用于阻止当前线程，这可能是您没有看到更新的原因。

MSDN

强制控件使其客户区无效并立即重绘自身和任何子控件。 Tell me more...

在实践中，您可能需要调查使用计时器而不是紧密循环和睡眠。

Answer 2

使用async标记您的方法，然后使用await Task.Delay(1);代替Sleep()。这将使应用程序保持响应，并允许UI在PictureBox的大小发生变化时实际重绘自己：

private async void button1_Click(object sender, EventArgs e)
{
    while (pictureBox2.Size.Width > 0)
    {
        int width = pictureBox2.Size.Width;
        width -= 2;
        pictureBox2.Size = new Size(width, pictureBox2.Size.Height);
        pictureBox2.Location = new Point(pictureBox2.Location.X + 1, pictureBox2.Location.Y);
        await Task.Delay(1);
    }
    pictureBox1.Image = currentImage;
    while (pictureBox2.Size.Width < 191)
    {
        int width = pictureBox2.Size.Width;
        width += 2;
        pictureBox2.Size = new Size(width, pictureBox2.Size.Height);
        pictureBox2.Location = new Point(pictureBox2.Location.X - 1, pictureBox2.Location.Y);
        await Task.Delay(1);
    }
}

图片尺寸缩小，但不会长回来？

2 个答案: