Question

我正在显示一个小工具提示，但如果我更改了dropdown菜单中的selecteditem / text，工具提示会显示旧文本和新文本。我希望它只显示新文本。

private void optionsvalueComboBox_MouseHover(object sender, EventArgs e)
{
    ToolTip buttonToolTip = new ToolTip();
    buttonToolTip.ToolTipTitle = "Value";
    buttonToolTip.UseFading = true;
    buttonToolTip.UseAnimation = true;
    buttonToolTip.IsBalloon = true;
    buttonToolTip.ShowAlways = true;
    buttonToolTip.AutoPopDelay = 5000;
    buttonToolTip.InitialDelay = 1000;
    buttonToolTip.ReshowDelay = 0;

    buttonToolTip.SetToolTip(optionsvalueComboBox, optionsvalueComboBox.Text);
}

Answer 1

假设您不喜欢的是工具提示文本从旧文本更改为新文本...

之所以这样做，是因为您正在每个悬停事件上创建一个新的工具提示实例。每次触发悬停事件时，旧的工具提示实例都会替换为新的工具提示实例，这就是您同时看到这两个实例的原因。要解决此问题，请将声明置于事件之外，如下所示：

ToolTip buttonToolTip = new ToolTip();

private void optionsvalueComboBox_MouseHover(object sender, EventArgs e)
{
    buttonToolTip.ToolTipTitle = "Value";
    buttonToolTip.UseFading = true;
    buttonToolTip.UseAnimation = true;
    buttonToolTip.IsBalloon = true;
    buttonToolTip.ShowAlways = true;
    buttonToolTip.AutoPopDelay = 5000;
    buttonToolTip.InitialDelay = 1000;
    buttonToolTip.ReshowDelay = 0;

    buttonToolTip.SetToolTip(optionsvalueComboBox, optionsvalueComboBox.Text);
  }

现在使用相同的工具提示，只需更换措辞。如果这对您有用，请告诉我！

Answer 2

我尝试挖掘MouseHover的{{1}}事件，看起来像我们预期的那样无法正常工作。只有当ComboBox的{{1}}样式为MouseHover时，将鼠标移到drop down button上时，ComboBox实际上才会触发。对此最简单的解决方案是将组合框样式更改为dropdown，如下所示：

dropdownlist

然而，这种风格会使comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;只读。如果这不是您想要的，那么您可以使用事件ComboBox和MouseMove来模仿Timer，这里有适合您的代码：

MouseHover

Answer 3

一个完整的工作示例：

[Serializable, StructLayout(LayoutKind.Sequential)]
public struct RECT
{
    public RECT(Rectangle rect)
    {
        Left = rect.Left;
        Top = rect.Top;
        Right = rect.Right;
        Bottom = rect.Bottom;
    }

    public Rectangle Rect
    {
        get
        {
            return new Rectangle(Left, Top, Right - Left, Bottom - Top);
        }
    }

    public Point Location
    {
        get
        {
            return new Point(Left, Top);
        }
    }

    public int Left;
    public int Top;
    public int Right;
    public int Bottom;
}

public class ToolTipComboBox: ComboBox
{
    #region Fields

    private ToolTip toolTip;
    private bool _tooltipVisible;
    private bool _dropDownOpen;
    #endregion

    #region Types

    [StructLayout(LayoutKind.Sequential)]
    // ReSharper disable once InconsistentNaming
    public struct COMBOBOXINFO
    {
        public Int32 cbSize;
        public RECT rcItem;
        public RECT rcButton;
        public ComboBoxButtonState buttonState;
        public IntPtr hwndCombo;
        public IntPtr hwndEdit;
        public IntPtr hwndList;
    }

    public enum ComboBoxButtonState
    {
        // ReSharper disable once UnusedMember.Global
        StateSystemNone = 0,
        // ReSharper disable once UnusedMember.Global
        StateSystemInvisible = 0x00008000,
        // ReSharper disable once UnusedMember.Global
        StateSystemPressed = 0x00000008
    }

    [DllImport("user32.dll")]
    public static extern bool GetComboBoxInfo(IntPtr hWnd, ref COMBOBOXINFO pcbi);
    [DllImport("user32.dll", SetLastError = true)]
    public static extern bool GetWindowRect(IntPtr hwnd, out RECT lpRect);

    #endregion

    #region Properties

    private IntPtr HwndCombo
    {
        get
        {
            COMBOBOXINFO pcbi = new COMBOBOXINFO();
            pcbi.cbSize = Marshal.SizeOf(pcbi);
            GetComboBoxInfo(Handle, ref pcbi);
            return pcbi.hwndCombo;
        }
    }

    private IntPtr HwndDropDown
    {
        get
        {
            COMBOBOXINFO pcbi = new COMBOBOXINFO();
            pcbi.cbSize = Marshal.SizeOf(pcbi);
            GetComboBoxInfo(Handle, ref pcbi);
            return pcbi.hwndList;
        }
    }

    [Browsable(false)]
    public new DrawMode DrawMode
    {
        get { return base.DrawMode; }
        set { base.DrawMode = value; }
    }

    #endregion

    #region ctor

    public ToolTipComboBox()
    {
        toolTip = new ToolTip
        {
            UseAnimation = false,
            UseFading = false
        };

        base.DrawMode = DrawMode.OwnerDrawFixed;
        DrawItem += OnDrawItem;
        DropDownClosed += OnDropDownClosed;
        DropDown += OnDropDown;
        MouseLeave += OnMouseLeave;
    }

    #endregion

    #region Methods

    private void OnDropDown(object sender, EventArgs e)
    {
        _dropDownOpen = true;
    }

    private void OnMouseLeave(object sender, EventArgs e)
    {
        ResetToolTip();
    }

    private void ShowToolTip(string text, int x, int y)
    {
        toolTip.Show(text, this, x, y);
        _tooltipVisible = true;
    }

    private void OnDrawItem(object sender, DrawItemEventArgs e)
    {
        ComboBox cbo = sender as ComboBox;
        if (e.Index == -1) return;

        // ReSharper disable once PossibleNullReferenceException
        string text = cbo.GetItemText(cbo.Items[e.Index]);
        e.DrawBackground();

        if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
        {
            TextRenderer.DrawText(e.Graphics, text, e.Font, e.Bounds.Location, SystemColors.Window);

            if (_dropDownOpen)
            {
                Size szText = TextRenderer.MeasureText(text, cbo.Font);
                if (szText.Width > cbo.Width - SystemInformation.VerticalScrollBarWidth && !_tooltipVisible)
                {
                    RECT rcDropDown;
                    GetWindowRect(HwndDropDown, out rcDropDown);

                    RECT rcCombo;
                    GetWindowRect(HwndCombo, out rcCombo);

                    if (rcCombo.Top > rcDropDown.Top)
                    {
                        ShowToolTip(text, e.Bounds.X, e.Bounds.Y - rcDropDown.Rect.Height - cbo.ItemHeight - 5);
                    }
                    else
                    {
                        ShowToolTip(text, e.Bounds.X, e.Bounds.Y + cbo.ItemHeight - cbo.ItemHeight);
                    }
                }
            }
        }
        else
        {
            ResetToolTip();
            TextRenderer.DrawText(e.Graphics, text, e.Font, e.Bounds.Location, cbo.ForeColor);
        }

        e.DrawFocusRectangle();
    }

    private void OnDropDownClosed(object sender, EventArgs e)
    {
        _dropDownOpen = false;
        ResetToolTip();
    }

    private void ResetToolTip()
    {
        if (_tooltipVisible)
        {
            // ReSharper disable once AssignNullToNotNullAttribute
            toolTip.SetToolTip(this, null);
            _tooltipVisible = false;
        }
    }

    #endregion
}

使用ComboBox显示工具提示（dropdownmenu）

3 个答案: