我如何找到集中在哪个控件上?

看起来wm_setfocus消息没有通过….我的错。我很肯定他们会通过 Control.WndProc 方法。为了解决这个问题,我不得不求助于 GetFocus 每次有消息出现并存储具有焦点的控件的句柄。

第一个代码部分是筛选类,第二个代码部分是测试代码。

    public class LastFocusedControlFilter : IMessageFilter
    {
        [DllImport("user32")]
        private static extern IntPtr GetFocus();

        private IntPtr? _lastCtrl;
        private readonly Control _ctrlToIgnore;

        public LastFocusedControlFilter(Control controlToIgnore)
        {
            _ctrlToIgnore = controlToIgnore;
        }

        public bool PreFilterMessage(ref Message m)
        {
            if (!_ctrlToIgnore.IsHandleCreated || _ctrlToIgnore.Disposing || _ctrlToIgnore.IsDisposed)
            {
                return false;
            }
            IntPtr handle = GetFocus();
            if (handle != _ctrlToIgnore.Handle)
            {
                _lastCtrl = handle;
            }
            return false;
        }

        public Control GetLastFocusedControl()
        {
            return _lastCtrl.HasValue ? Control.FromHandle(_lastCtrl.Value) : null;
        }
    }

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        using (Form form = new Form())
        {
            Action resetBackColor = null;
            for (int i = 0; i < 10; i++)
            {
                TextBox textBox = new TextBox();
                resetBackColor += delegate { textBox.BackColor = Color.White; };
                textBox.Text = ((char)('a' + i)).ToString();
                textBox.Location = new Point(0, textBox.Height * i);
                form.Controls.Add(textBox);
            }
            Button showTextButton = new Button();
            LastFocusedControlFilter msgFilter = new LastFocusedControlFilter(showTextButton);
            showTextButton.Dock = DockStyle.Bottom;
            showTextButton.Text = "Show text of last selected control";
            showTextButton.Click += delegate(object sender, EventArgs e)
             {
                 resetBackColor();
                 Control lastControl = msgFilter.GetLastFocusedControl();
                 if (lastControl == null)
                 {
                     MessageBox.Show("No control previous had focus.");
                 }
                 else
                 {
                     lastControl.BackColor = Color.Red;
                     MessageBox.Show(string.Format("Control of type {0} had focus with text '{1}'.", lastControl.GetType(), lastControl.Text));
                 }
             };
            form.Controls.Add(showTextButton);

            Application.AddMessageFilter(msgFilter);
            Application.Run(form);
        }
    }
}

添加一个 IMessageFilter 和监视Windows消息,如 WM_SETFOCUS 或 WM_ACTIVATE . 你可以使用 Control.FromHandle 将Intprs转换为.NET控件。

找到一个更简单的方法-

[Parent Form].ActiveMdiChild.ActiveControl

您可以向项目中添加这样的类:

public class FocusWatcher
{
    private static System.Windows.Forms.Control _focusedControl;
    public static System.Windows.Forms.Control FocusedControl
    {
        get
        {
            return _focusedControl;
        }
    }

    public static void GotFocus(object sender, EventArgs e)
    {
        _focusedControl = (System.Windows.Forms.Control)sender;
    }
}

然后,对于您希望成为“最近焦点控制”候选的任何表单上的任何控件,您可以执行以下操作:

textBox1.GotFocus += FocusWatcher.GotFocus;

然后访问 FocusWatcher.FocusedControl 以获得最近的集中控制。监视消息将起作用,但您必须忽略不需要的消息(如从MDI窗体激活wm_)。

您可以遍历每个窗体上的所有控件,并为gotfocus事件添加此处理程序,但确实有一些控件 不要 希望这样做(例如按钮)。您可以迭代并只添加文本框的处理程序。