如何处理 WinForms 中的 ErrorProvider 图标上的鼠标单击或鼠标按下

Question

我想在某些时候在按钮上显示错误提供程序图标，如下所示：

但是，如果用户在打算单击按钮时碰巧单击该图标，我也不希望该图标遮盖/阻止按钮单击，也许是因为悬停时的错误消息显示“单击此处修复”之类的内容.

ErrorProvider 没有事件（好吧，它有一个不相关的事件）。 我尝试使用本文中描述的方法，但问题是当我单击错误图标时，甚至没有出现预过滤消息。 这是我的示例代码：

public partial class Form1 : Form, IMessageFilter
{
    public Form1()
    {
        InitializeComponent();
        errorProvider1.SetIconPadding(button1, -27);
        errorProvider1.SetError(button1, "error");
        Application.AddMessageFilter(this);
    }

    public bool PreFilterMessage(ref Message m)
    {
        var ctrl = Control.FromHandle(m.HWnd);
        var msg = m.Msg;

        // the values in the "ignore" list below are all movement/paint events
        if (ctrl is Button b && (!(new[] { 15, 512, 675, 280, 673 }.Any((v) => msg == v))))
        {
            // only gets here when un-obscured button surface is clicked.
        }

        // this only ever prints form and button
        if (ctrl != null) System.Diagnostics.Debug.Print($"{ctrl.GetType().Name}"); 

        return false;
    }
}

有什么办法可以做到这一点吗？

Answer 1

当您想在按钮内显示错误图标时，您可以通过手动绘制图标并显式使用

ErrorProvider

 来轻松伪造 

ToolTip

：

public partial class FakeErrorProvider : Form
{
    private static Icon _errorIcon = new ErrorProvider().Icon;
    private static int _errorIconPadding = 4;

    private ToolTip _toolTip;
    private bool _hasError;

    public FakeErrorProvider()
    {
        InitializeComponent();

        _toolTip = new ToolTip();
        button1.Click += Button1_Click;
        button1.Paint += Button1_Paint;
        button1.MouseMove += Button1_MouseMove;
    }

    private void Button1_Click(object? sender, EventArgs e)
    {
        // fixing the error only when the error icon is clicked
        if (!_hasError || GetErrorRectangle(button1).Contains(button1.PointToClient(Cursor.Position)))
            _hasError = !_hasError;
        button1.Invalidate();
        if (!_hasError)
            _toolTip.SetToolTip(button1, String.Empty);
    }

    private void Button1_Paint(object? sender, PaintEventArgs e)
    {
        // showing the error icon
        if (_hasError)
            e.Graphics.DrawIcon(_errorIcon, GetErrorRectangle(button1));
    }

    private void Button1_MouseMove(object? sender, MouseEventArgs e)
    {
        // displaying the error tooltip only when the cursor is above the error icon
        bool isVisible = _toolTip.GetToolTip(button1).Length > 0;
        if (_hasError && !isVisible && GetErrorRectangle(button1).Contains(e.Location))
            _toolTip.SetToolTip(button1, "click here to fix");
        else if (isVisible && (!_hasError || !GetErrorRectangle(button1).Contains(e.Location)))
            _toolTip.SetToolTip(button1, String.Empty);
    }

    private Rectangle GetErrorRectangle(Button button)
    {
        var rect = new Rectangle(Point.Empty, _errorIcon.Size);
        rect.Offset(button.Width - rect.Width - _errorIconPadding, button.Height / 2 - rect.Height / 2);
        return rect;
    }
}

结果：