Question

这是我的代码：

public partial class Form1 : Form
{
    Graphics g;
    bool mouseUP = false;
    double dimensions = 4.0;
    SolidBrush brush;

    public Form1()
    {
        InitializeComponent();
        g = this.CreateGraphics();
        brush = new SolidBrush(Color.Black);
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        mouseUP = false;
        backgroundWorker1.RunWorkerAsync(e);
    }

    private bool mouseIsUP()
    {
        return mouseUP;
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        mouseUP = true;
        MessageBox.Show("UP");
    }

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        backgroundWorker1.ReportProgress(0,e.Argument);  
    }

    private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        while (!mouseIsUP())
        {
            g.FillEllipse(brush, ((MouseEventArgs)e.UserState).X - (int)dimensions / 2, ((MouseEventArgs)e.UserState).Y - (int)dimensions / 2, (int)dimensions, (int)dimensions);
            dimensions += 0.2;
            Thread.Sleep(10);
        }
    }
}

为什么事件mouseUP永远不会发生？如果我删除了，我可以看到MessageBox“UP”...

我正在尝试在按下鼠标时制作更大的椭圆。当我释放鼠标按钮时，椭圆不应该长得更多。

提前致谢！

Answer 1

因为您没有将事件处理程序绑定到事件（假设您没有错过该代码）。

例如，在Form1的构造函数中，您可以添加

MouseUp += Form1_MouseUp;
MouseDown += Form1_MouseDown;

Answer 2

看起来后台工作者以某种方式阻止了代码中的事件循环。 DoWork在哪里召唤工人？

我认为更好的解决办法可能是覆盖OnPaint方法，检查鼠标是否在那里，然后绘制圆圈。

bool isMouseDown = false;
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
    isMouseDown = true;
}
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
    isMouseDown = false;
}
protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);
    if (isMouseDown)
    {
        g.FillEllipse(brush, ((MouseEventArgs)e.UserState).X - (int)dimensions / 2, ((MouseEventArgs)e.UserState).Y - (int)dimensions / 2, (int)dimensions, (int)dimensions);
        dimensions += 0.2;
        Thread.Sleep(10);

    }
}

在一段时间内捕获mouseUP事件

2 个答案: