Csharp 如何设置WinForms按钮焦点，使其看起来像是被Tab键插入其中

确保第一个按钮是带有TabIndex=0的"One and Only"控件，这样它才能获得焦点，但这和被Tab键插入之间应该没有区别.

如果你 Select "定制油漆"，你可以通过手动将所有的Button换成设计者.cs文件中的ButtonEx来使它的侵害性降到最低.然后，只需很少的代码，就可以拥有外焦点提示实心边框和虚线焦点矩形的设计时属性.

class ButtonEx : Button
{
    public Color FocusRectangleColor
    {
        get => _focusRectangleColor;
        set
        {
            if (!Equals(_focusRectangleColor, value))
            {
                _focusRectangleColor = value;
                Refresh();
            }   
        }
    }
    Color _focusRectangleColor = Color.Red;

    public Color FocusCueColor
    {
        get => _focusCueColor;
        set
        {
            if (!Equals(_focusCueColor, value))
            {
                _focusCueColor = value;
                Refresh();
            }
        }
    }
    Color _focusCueColor = default;

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        if (Enabled && Focused && (MouseButtons == MouseButtons.None))
        {
            if (FocusRectangleColor != default)
            {
                using (Pen dottedPen = new Pen(FocusRectangleColor, 2f))
                {
                    dottedPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot;
                    Rectangle focusRect = this.ClientRectangle;
                    focusRect.Inflate(-12, -12);
                    e.Graphics.DrawRectangle(dottedPen, focusRect);
                }
            }
            if (FocusCueColor != default)
            {
                using (Pen cuePen = new Pen(FocusCueColor, FlatAppearance.BorderSize))
                {
                    Rectangle focusRect = this.ClientRectangle;
                    focusRect.Inflate(-2, -2);
                    e.Graphics.DrawRectangle(cuePen, focusRect);
                }
            }
        }
    }
}

Testing个

在以下情况下，编写的代码应正确导航:

• [Tab]键用于导航.
• 鼠标用于点击按钮.
• 以编程方式调用button.Focus().
• 从当前聚焦的控件调用SelectNextControl().
• ActiveControl以编程方式设置.

为了举止得体:

• 需要正确设置TabOrder个控件
• 对于要标记的控件，TabStop属性应为true，否则为False.
• 该表单必须处于活动状态.
• 应该具有焦点的按钮必须具有最低的制表符索引.

Testbench

下面是我用TabIndex的值测试这个答案的代码，如VS Menu\View\Tab Order中所示.Clone.使用组合框，可以 Select 定时器模式，以在上面列表中导航的三个"程序化"选项之间循环.

public partial class MainForm : Form
{
    enum TimerMode { None, FocusNext, SelectNext, NextActive }
    public MainForm()
    {
        InitializeComponent();
        comboBoxTimers.Items.AddRange(Enum.GetValues(typeof(TimerMode)).OfType<object>().ToArray());
        comboBoxTimers.SelectedIndex = 0;
        comboBoxTimers.SelectionChangeCommitted += async(sender, e) =>
        {
            _timerMode = TimerMode.None;
            await _busy.WaitAsync();
            _timerMode = (TimerMode)(comboBoxTimers.SelectedItem ?? TimerMode.None);
            BeginInvoke(()=>ActiveControl = button1);
            string name;
            switch (_timerMode)
            {
                case TimerMode.FocusNext:
                    do
                    {
                        await Task.Delay(1000);
                        if (!comboBoxTimers.DroppedDown)
                        {
                            name = ActiveControl?.Name ?? string.Empty;
                            switch (name)
                            {
                                case nameof(button1): button2.Focus(); break;
                                case nameof(button2): button3.Focus(); break;
                                default: case nameof(button3): button1.Focus(); break;
                            }
                        }
                    } while (_timerMode == TimerMode.FocusNext);
                    _busy.Release();
                    break;
                case TimerMode.SelectNext:
                    do
                    {
                        await Task.Delay(1000);
                        if (!comboBoxTimers.DroppedDown)
                        {
                            if (ActiveControl != null) SelectNextControl(
                                ctl: ActiveControl,
                                forward: true,
                                tabStopOnly: true,
                                nested: true,
                                wrap: true
                            );
                        }
                    } while (_timerMode == TimerMode.SelectNext);
                    _busy.Release();
                    break;
                case TimerMode.NextActive:
                    do
                    {
                        await Task.Delay(1000);
                        if (!comboBoxTimers.DroppedDown)
                        {
                            name = ActiveControl?.Name ?? string.Empty;
                            switch (name)
                            {
                                case nameof(button1): ActiveControl = button2; break;
                                case nameof(button2): ActiveControl = button3; break;
                                default: case nameof(button3): ActiveControl = button1; break;
                            }
                        }
                    } while (_timerMode == TimerMode.NextActive);
                    _busy.Release();
                    break;
            }
        };
    }
    TimerMode _timerMode = TimerMode.None;
    SemaphoreSlim _busy = new SemaphoreSlim(1, 1);
}