TabControl填充会导致TabPage中的隐藏控件重新排序不正确

控件 Handles Parent Control 当 TabControl Padding 属性已更改。看着 .NET 源代码, 衬垫 打电话给 RecreateHandle();

下面是说明问题的代码。每个 checkbox label 就在它下面。有些标签在开始时是可见的,有些是隐藏的。检查 person0 复选框使 个人0 FlowLayoutPanel . 见截图。

代码提供了一个 bool doWorkaround 但一定有更好的办法。强迫所有 把手 将使用 CreateControl() 似乎也不正确。

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Windows.Forms;

namespace WindowsFormsApplication3 {

public class TabControl3 : TabControl {

    private bool doWorkaround = false; // set to true to prevent the bug

    protected override void OnFontChanged(EventArgs e) {
        base.OnFontChanged(e);
        int h = (int) this.Font.Height;
        SetPadding(new Point(h, h)); // calling this causes the Controls to re-order incorrectly
    }

    ///<summary>Setting the padding causes the TabControl to recreate all the handles, which causes the hidden handleless controls to rearrange.</summary>
    public virtual void SetPadding(Point pt) {
        // Workaround solution: remove all controls from tab pages and then add them back after.
        int n = TabPages.Count;
        Control[][] arr = null;
        if (doWorkaround) {
            arr = new Control[n][];
            for (int i = 0; i < n; i++) {
                TabPage tp = TabPages[i];
                arr[i] = tp.Controls.Cast<Control>().ToArray();
                tp.Controls.Clear();
            }
        }

        this.Padding = pt; // in the .NET source code, setting Padding calls RecreateHandle()

        if (doWorkaround) {
            for (int i = 0; i < n; i++)
                TabPages[i].Controls.AddRange(arr[i]);
        }
    }
}

public class CheckBox2 : CheckBox {
    public CheckBox2(String text, bool isChecked = false) : base() {
        this.Text = text;
        this.AutoSize = true;
        this.Checked = isChecked;
    }
}

public class Label2 : Label {
    public Label2(String text) : base() {
        this.Text = text;
        this.AutoSize = true;
    }
}

public class MyForm : Form {

    TabControl tc = new TabControl3 { Dock = DockStyle.Fill };

    public MyForm() {
        this.Size = new System.Drawing.Size(600, 800);
        this.StartPosition = FormStartPosition.CenterScreen;
        TabPage tp1 = new TabPage("Page1");

        FlowLayoutPanel p = new FlowLayoutPanel { FlowDirection = System.Windows.Forms.FlowDirection.TopDown, Dock = DockStyle.Fill };

        p.Controls.Add(new CheckBox2("Person0"));
        p.Controls.Add(new Label2("Person0") { Visible = false });

        p.Controls.Add(new CheckBox2("Person1", true));
        p.Controls.Add(new Label2("Person1"));

        p.Controls.Add(new CheckBox2("Person2", true));
        p.Controls.Add(new Label2("Person2"));

        p.Controls.Add(new CheckBox2("Person3"));
        p.Controls.Add(new Label2("Person3") { Visible = false });

        p.Controls.Add(new CheckBox2("Person4"));
        p.Controls.Add(new Label2("Person4") { Visible = false });

        for (int i = 0; i < p.Controls.Count; i += 2) {
            CheckBox cb = (CheckBox) p.Controls[i];
            Label lb = (Label) p.Controls[i+1];
            cb.CheckedChanged += delegate {
                bool b = cb.Checked;
                lb.Visible = b;
            };
        }

        tp1.Controls.Add(p);
        tc.TabPages.Add(tp1);

        Controls.Add(tc);
    }

    protected override void OnLoad(EventArgs e) {
        base.OnLoad(e);
        this.Font = SystemFonts.MenuFont; // to trigger the bug
    }
}

static class Program {
    [STAThread]
    static void Main() {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new MyForm());
    }
}
}

我用 .NET 3.5, 4, 4.52