是什么让Winform的位置最初陈旧？

Question

下面的代码演示了一个非常简单的问题; 我希望我只是错过了某人可能能够揭示的环境.

目标

(1)启动主winform(MainForm).
(2)按下按钮显示半透明的二级winform(ShadowForm),并且应该完全覆盖MainForm.

实际发生了什么

场景1:启动主winform,然后按下按钮:ShadowForm显示正确的大小但不正确的位置,向下和向右(就像它是级联的).按按钮再次关闭ShadowForm.再按一次按钮重新打开ShadowForm,现在它处于正确位置,覆盖MainForm.

场景2:启动主winform,移动它,然后按下按钮:ShadowForm显示正确的大小但位置不正确(MainForm在移动之前的位置).按按钮关闭; 再次按下重新打开,现在ShadowForm处于正确的位置.

using System;
using System.Windows.Forms;

namespace LocationTest
{
    static class Program
    {
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MainForm());
        }
    }

    public class MainForm : Form
    {
        ShadowForm shadowForm = new ShadowForm();
        Button button1 = new Button();
        System.ComponentModel.IContainer components = null;

        public MainForm()
        {
            this.SuspendLayout();
            this.button1.Location = new System.Drawing.Point(102, 44);
            this.button1.Size = new System.Drawing.Size(75, 23);
            this.button1.Text = "button1";
            this.button1.Click += new System.EventHandler(this.button1_Click);
            this.ClientSize = new System.Drawing.Size(292, 266);
            this.Controls.Add(this.button1);
            this.ResumeLayout(false);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (shadowForm.Visible) { shadowForm.Hide(); }
            else
            {
                shadowForm.Size = Size; // this always works
                shadowForm.Location = Location; // this fails first time, but works second time!
                shadowForm.Show();
            }
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null)) { components.Dispose(); }
            base.Dispose(disposing);
        }
    }

    public class ShadowForm : Form
    {
        private System.ComponentModel.IContainer components = null;

        public ShadowForm()
        {
            this.SuspendLayout();
            this.BackColor = System.Drawing.Color.Black;
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
            this.Opacity = 0.5;
            this.Click += new System.EventHandler(this.ShadowForm_Click);
            this.ResumeLayout(false);
        }

        private void ShadowForm_Click(object sender, EventArgs e)
        {
            Hide();
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null)) { components.Dispose(); }
            base.Dispose(disposing);
        }
    }
}

Answer 1

在第一次设置位置之前,应将StartPosition设置为手动.

shadowForm.StartPosition = FormStartPosition.Manual;
shadowForm.Size = Size; // this always works
shadowForm.Location = Location; // this fails first time, but works second time!
shadowForm.Show();

或者像乔尔建议的那样:

shadowForm.StartPosition = FormStartPosition.CenterParent;  // Location shouldn't need to be set
shadowForm.Size = Size; // this always works
shadowForm.Show();