在焦点上更改组合框的边框颜色 [英] Changing the border color of a Combobox on focus

问题描述

我有一个自定义的ComboBox.

我想给 ComboBox 一个自定义的 BorderColor，当它被聚焦时.

I want to give a custom BorderColor to the ComboBox, when it is focused.

为此，我使用以下代码:

To do this, I'm using the following code:

Graphics g = Graphics.FromHwnd(Handle);
Rectangle bounds = new Rectangle(0, 0, Width, Height);

ControlPaint.DrawBorder(g, bounds, BaseConfigurations.StyleColor, ButtonBorderStyle.Solid);

问题是，如果我在 MouseHover 事件中使用代码当我在 ComboBox 控件上移动鼠标时，我可以看到它起作用了.但是，相同的代码在 GotFocus 事件中不起作用，我不知道为什么......感谢任何帮助.

The thing is, if I use the code inside the MouseHover event when I move the mouse on the ComboBox control, I can see that it works. However, the same code does not work inside the GotFocus Event, and I can't figure out why.. any help is appreciated.

推荐答案

这是一个简单的类，它继承自 ComboBox 并公开了两个允许设置控件的活动和非活动边框的属性.

This is a simple Class that inherits from ComboBox and exposes two properties that allows to set the Active and Inactive border of the Control.

使用父窗体 Paint() 事件完成绘制，仅使所选控件周围的区域无效.

The painting is done using the Parent Form Paint() event, invalidating only the area around the selected control.

Parent Paint() 事件在自定义 ComboBox OnHandleCreated() 事件中订阅，连同控件的 Enter()，Leave() 和 Move() 事件.
需要订阅Move() 事件才能绘制透明边框，否则在设计时拖动控件时边框将保持绘制在父客户区.

The Parent Paint() event is subscribed in the custom ComboBox OnHandleCreated() event, along with the control's Enter(), Leave() and Move() events.
Subscribing the Move() event is required to paint a transparent border, otherwise the border will remain painted on the Parent client area while dragging the control at Design time.

我还添加了 DropDownBackColor() 和 DropDownForeColor() 属性，如果自定义 ComboBox DrawMode 设置为 OwnerDrawVariable(像往常一样).

I've also added DropDownBackColor() and DropDownForeColor() properties, which become active if the custom ComboBox DrawMode is set to OwnerDrawVariable (as usual).

这是它的样子:

This is how it looks like:

public class CustomCombo : ComboBox
{
    private Color ActionBorderColor = Color.Empty;
    public CustomCombo()
    {
        InitializeComponent();
    }

    public Color BorderActive { get; set; }
    public Color BorderInactive { get; set; }
    public Color DropDownBackColor { get; set; }
    public Color DropDownForeColor { get; set; }

    private void InitializeComponent()
    {
        this.DrawMode = DrawMode.OwnerDrawVariable;
        this.BorderActive = Color.OrangeRed;
        this.BorderInactive = Color.Transparent;
        this.DropDownBackColor = Color.FromKnownColor(KnownColor.Window);
        this.DropDownForeColor = this.ForeColor;
        this.HandleCreated += new EventHandler(this.OnControlHandle);
    }

    protected void OnControlHandle(object sender, EventArgs args)
    {
        Form parent = this.FindForm();
        parent.Paint += new PaintEventHandler(this.ParentPaint);
        this.Enter += (s, ev) => { this.InvalidateParent(BorderActive); };
        this.Leave += (s, ev) => { this.InvalidateParent(BorderInactive); };
        this.Move += (s, ev) => { this.InvalidateParent(Color.Transparent); };
        base.OnHandleCreated(e);
    }

    private void InvalidateParent(Color bordercolor)
    {
        ActionBorderColor = bordercolor;
        Rectangle rect = this.Bounds;
        rect.Inflate(2, 2);
        this.FindForm().Invalidate(rect);
    }

    protected void ParentPaint(object sender, PaintEventArgs e)
    {
        Rectangle rect = this.Bounds;
        rect.Inflate(1, 1);
        using (Pen pen = new Pen(ActionBorderColor, 1))
            e.Graphics.DrawRectangle(pen, rect);
    }

    protected override void OnDrawItem(DrawItemEventArgs e)
    {
        using (SolidBrush bkBrush = new SolidBrush(this.DropDownBackColor))
            e.Graphics.FillRectangle(bkBrush, e.Bounds);
        using (SolidBrush foreBbrush = new SolidBrush(this.DropDownForeColor))
            e.Graphics.DrawString(this.Items[e.Index].ToString(),
                                  this.Font, foreBbrush, new PointF(e.Bounds.X, e.Bounds.Y));
        e.DrawFocusRectangle();
    }
}

这篇关于在焦点上更改组合框的边框颜色的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！