Control.MouseWheel事件

Question

我創建了一個簡單的應用程序，用鼠標滾輪縮放圖片框內的圖像。它在我的開發筆記本電腦（Win10）上運行完美。但是當我在臺式電腦（Win7）上運行它時，縮放（使用鼠標滾輪）功能不起作用。

下面是我的我執行段：

 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); 
      } 
     } 
    } 

我覺得這是我的桌面PC上的Control.MouseWheel事件的問題。當我調試時，這個事件從來沒有出現，雖然我已經集中或點擊圖片框內。當我通過過濾WM_MOUSEWHEEL = 0x20a;消息來嘗試其他實現時，它可以在我的筆記本電腦和我的桌面上運行。任何想法爲什麼這些不同的行爲發生？感謝您的時間。

Answer 1

事實證明，Win 10有一個系統選項叫做「Scroll inactive windows when I hover over them」。這就是爲什麼我以前的代碼只能在Win 10機器上工作，我添加了下面幾行來修復它。 HansPassant的技巧

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