Control.MouseWheel事件

Question

我创建了一个简单的应用程序，用鼠标轮放大图片框中的图像。它在我的开发笔记本电脑(Win10)上运行得很好。但是当我在台式机(Win7)上运行它时，缩放(使用鼠标轮)功能就不能工作了。

下面是我实现的片段：

        private void InitializeComponent()
    {
        this.pictureBox1 = new System.Windows.Forms.PictureBox();
        this.panel1 = new System.Windows.Forms.Panel();
        ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit();
        this.panel1.SuspendLayout();
        this.SuspendLayout();
        // 
        // pictureBox1
        // 
        this.pictureBox1.Location = new System.Drawing.Point(4, 0);
        this.pictureBox1.Margin = new System.Windows.Forms.Padding(4);
        this.pictureBox1.Name = "pictureBox1";
        this.pictureBox1.Size = new System.Drawing.Size(493, 583);
        this.pictureBox1.SizeMode = System.Windows.Forms.PictureBoxSizeMode.AutoSize;
        this.pictureBox1.TabIndex = 0;
        this.pictureBox1.TabStop = false;
        this.pictureBox1.Click += new System.EventHandler(this.pictureBox1_Click);
        this.pictureBox1.MouseDown += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseDown);
        this.pictureBox1.MouseMove += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseMove);
        this.pictureBox1.MouseUp += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseUp);
        this.pictureBox1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseWheel);
        // 
        // panel1
        // 
        this.panel1.AutoScroll = true;
        this.panel1.AutoSize = true;
        this.panel1.Controls.Add(this.pictureBox1);
        this.panel1.Location = new System.Drawing.Point(1, 2);
        this.panel1.Name = "panel1";
        this.panel1.Size = new System.Drawing.Size(714, 593);
        this.panel1.TabIndex = 1;
        // 
        // Form1
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 16F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.AutoScroll = true;
        this.ClientSize = new System.Drawing.Size(719, 594);
        this.Controls.Add(this.panel1);
        this.Margin = new System.Windows.Forms.Padding(4);
        this.Name = "Form1";
        this.Text = "Form1";
        this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(this.Form1_FormClosing);
        ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit();
        this.panel1.ResumeLayout(false);
        this.panel1.PerformLayout();
        this.ResumeLayout(false);
        this.PerformLayout();

    }

private float ZOOM = 1.5f
private void pictureBox1_MouseWheel(object sender, System.Windows.Forms.MouseEventArgs e)
    {
        pictureBox1.Focus();
        if (e.Delta < 0) //ZoomIn
        {
            Console.WriteLine("Mouse Wheel Zoom In");

            if ((pictureBox1.Width < panel1.Width) && (pictureBox1.Height < panel1.Height))
            {
                pictureBox1.Width = Convert.ToInt32(pictureBox1.Width * ZOOM);
                pictureBox1.Height = Convert.ToInt32(pictureBox1.Height * ZOOM);
                pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;

                this.Refresh();                    
            }

        }
        else
        {
            //ZoomOut
            Console.WriteLine("Mouse Wheel Zoom Out");
            if ((pictureBox1.Width > panel1.Width) &&
            (pictureBox1.Height > panel1.Height))
            {
                pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
                pictureBox1.Width = Convert.ToInt32(pictureBox1.Width / ZOOM);
                pictureBox1.Height = Convert.ToInt32(pictureBox1.Height / ZOOM);
            }
        }
    }

我认为这是我的桌面PC上的Control.MouseWheel事件的问题所在。调试时，虽然我已经在图片框中聚焦或单击，但从未出现此事件。当我尝试通过过滤WM_MOUSEWHEEL = 0x20a;消息使用其他实现时，它在我的笔记本电脑和我的台式机上都能工作。知道为什么会发生这些不同的行为吗？谢谢您抽时间见我。

Answer 1

原来，Win 10有一个系统选项，名为“当我悬停在窗口上时，不活动的窗口”。这就是为什么我以前的代码只在Win 10机器上工作。我添加了下面的行来修复它。谢谢@HansPassant的提示。

    private void picBox_MouseHover(object sender, EventArgs e)
    {
        picBox.Focus();
    }