c# - 捕捉文本框滚动事件？

Question

文本框或richtextbox，我唯一想要的是在滚动条移动时触发一个功能。

我已经找到了 GetScrollPos 和 SetScrollPos。我想过定期检查滚动条的位置，但必须有更好的方法。那么，更好的方法是什么？

更新：使用 WinForms

Answer 1

假设 WinForms，您可以尝试 pinvoking：

public class MyRTF: RichTextBox {

  private const int WM_HSCROLL = 0x114;
  private const int WM_VSCROLL = 0x115;
  private const int WM_MOUSEWHEEL = 0x20A;

  protected override void WndProc(ref Message m) {
    base.WndProc(ref m);

    if (m.Msg == WM_VSCROLL || m.Msg == WM_HSCROLL || m.Msg == WM_MOUSEWHEEL) {
      // scrolling...
    }
  }

}

Answer 2

修改了接受的答案以包括 Horizo​​ntalScrollPosition 和 VerticalScrollPosition 属性（用于获取和设置滚动位置）和 ScrollChanged 事件（使用 .NET 的 ScrollEventArgs）。ScrollChanged 还将在关键导航和文本修改以及选择拖动、控件调整大小和字体大小调整期间触发。

  /// <summary>
  /// TextBox with support for getting and setting the vertical scroll bar
  /// position, as well as listening to vertical scroll events.
  /// </summary>
  public class ScrollTextBox : System.Windows.Forms.TextBox
  {

     public ScrollTextBox()
     {  _components = new System.ComponentModel.Container();
        // Calculate width of "W" to set as the small horizontal increment
        OnFontChanged(null);
     }

     [  System.ComponentModel.DefaultValue(0)
     ,  System.ComponentModel.Category("Appearance")
     ,  System.ComponentModel.Description
        (  "Gets or sets the vertical scroll bar's position"
        )
     ]
     public int VerticalScrollPosition
     {  set { SetScroll(value, Win32.WM_VSCROLL, Win32.SB_VERT); }
        get { return GetScroll(Win32.SB_VERT); }
     } 

     [  System.ComponentModel.DefaultValue(0)
     ,  System.ComponentModel.Category("Appearance")
     ,  System.ComponentModel.Description
        (  "Gets or sets the horizontal scroll bar's position"
        )
     ]
     public int HorizontalScrollPosition
     {  set { SetScroll(value, Win32.WM_HSCROLL, Win32.SB_HORZ); }
        get { return GetScroll(Win32.SB_HORZ); }
     } 

     [  System.ComponentModel.Description
        (  "Fired when the scroll bar's vertical position changes"
        )
     ,  System.ComponentModel.Category("Property Changed")
     ]
     public event System.Windows.Forms.ScrollEventHandler ScrollChanged;

     // Fire scroll event if the scroll-bars are moved
     protected override void WndProc
     (  ref System.Windows.Forms.Message message
     ){ base.WndProc(ref message);
        if(message.Msg == Win32.WM_VSCROLL
        || message.Msg == Win32.WM_HSCROLL
        || message.Msg == Win32.WM_MOUSEWHEEL
        )  TryFireScrollEvent();
     }

     // Key-down includes navigation keys, but also typing and pasting can
     // cause a scroll event
     protected override void OnKeyDown
     (  System.Windows.Forms.KeyEventArgs e
     ){ base.OnKeyDown(e);
        TryFireScrollEvent();
     }

     protected override void OnKeyUp
     (  System.Windows.Forms.KeyEventArgs e
     ){ base.OnKeyUp(e);
        TryFireScrollEvent();
     }

     // Resizing can alter the word-wrap or fit the content causing the text
     // to scroll
     protected override void OnResize
     (  System.EventArgs e
     ){ base.OnResize(e);
        TryFireScrollEvent();
     }

     // Clicking an empty space can move the carot to the beginning of the
     // line causing a scroll event
     protected override void OnMouseDown
     (  System.Windows.Forms.MouseEventArgs e
     ){ base.OnMouseDown(e);
        TryFireScrollEvent();
     }

     protected override void OnMouseUp
     (  System.Windows.Forms.MouseEventArgs e
     ){ base.OnMouseUp(e);
        TryFireScrollEvent();
     }

     // If the mouse button is down, a text selection is probably being done
     // where dragging the selection can caues scroll events
     protected override void OnMouseMove
     (  System.Windows.Forms.MouseEventArgs e
     ){ base.OnMouseMove(e);
        if(e.Button != System.Windows.Forms.MouseButtons.None)
           TryFireScrollEvent();
     }

     // Changing the size of the font can cause a scroll event. Also, when
     // scrolling horizontally, the event will notify whether the scroll
     // was a large or small change. For vertical, small increments are 1
     // line, but for horizontal, it is several pixels. To guess what a
     // small increment is, get the width of the W character and anything
     // smaller than that will be represented as a small increment
     protected override void OnFontChanged
     (  System.EventArgs e
     ){ base.OnFontChanged(e);
        using(System.Drawing.Graphics graphics = this.CreateGraphics())
           _fontWidth = (int)graphics.MeasureString("W", this.Font).Width;
        TryFireScrollEvent();
     }

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

     private void SetScroll
     (  int value
     ,  uint windowsMessage
     ,  int scrollBarMessage
     ){ Win32.SetScrollPos
        (  (System.IntPtr)this.Handle
        ,  scrollBarMessage
        ,  value
        ,  true
        );
        Win32.PostMessage
        (  (System.IntPtr)this.Handle
        ,  windowsMessage
        ,  4 + 0x10000 * value
        ,  0
        );
     }

     private int GetScroll
     (  int scrollBarMessage
     ){ return Win32.GetScrollPos
        (  (System.IntPtr)this.Handle
        ,  scrollBarMessage
        );
     }

     // Fire both horizontal and vertical scroll events seperately, one
     // after the other. These first test if a scroll actually occurred
     // and won't fire if there was no actual movement
     private void TryFireScrollEvent()
     {  // Don't do anything if there is no event handler
        if(ScrollChanged == null)
           return;
        TryFireHorizontalScrollEvent();
        TryFireVerticalScrollEvent();
     }

     private void TryFireHorizontalScrollEvent()
     {

        // Don't do anything if there is no event handler
        if(ScrollChanged == null)
           return;

        int lastScrollPosition = _lastHorizontalScrollPosition;
        int scrollPosition = HorizontalScrollPosition;

        // Don't do anything if there was no change in position
        if(scrollPosition == lastScrollPosition)
           return;

        _lastHorizontalScrollPosition = scrollPosition;

        ScrollChanged
        (  this
        ,  new System.Windows.Forms.ScrollEventArgs
           (  scrollPosition < lastScrollPosition - _fontWidth
              ?  System.Windows.Forms.ScrollEventType.LargeDecrement
              :  scrollPosition > lastScrollPosition + _fontWidth
              ?  System.Windows.Forms.ScrollEventType.LargeIncrement
              :  scrollPosition < lastScrollPosition
              ?  System.Windows.Forms.ScrollEventType.SmallDecrement
              :  System.Windows.Forms.ScrollEventType.SmallIncrement
           ,  lastScrollPosition
           ,  scrollPosition
           ,  System.Windows.Forms.ScrollOrientation.HorizontalScroll
           )
        );

     }

     private void TryFireVerticalScrollEvent()
     {

        // Don't do anything if there is no event handler
        if(ScrollChanged == null)
           return;


        int lastScrollPosition = _lastVerticalScrollPosition;
        int scrollPosition = VerticalScrollPosition;

        // Don't do anything if there was no change in position
        if(scrollPosition == lastScrollPosition)
           return;

        _lastVerticalScrollPosition = scrollPosition;

        ScrollChanged
        (  this
        ,  new System.Windows.Forms.ScrollEventArgs
           (  scrollPosition < lastScrollPosition - 1
              ?  System.Windows.Forms.ScrollEventType.LargeDecrement
              :  scrollPosition > lastScrollPosition + 1
              ?  System.Windows.Forms.ScrollEventType.LargeIncrement
              :  scrollPosition < lastScrollPosition
              ?  System.Windows.Forms.ScrollEventType.SmallDecrement
              :  System.Windows.Forms.ScrollEventType.SmallIncrement
           ,  lastScrollPosition
           ,  scrollPosition
           ,  System.Windows.Forms.ScrollOrientation.VerticalScroll
           )
        );

     }

     private int _lastVerticalScrollPosition;
     private int _lastHorizontalScrollPosition;
     private int _fontWidth;
     private System.ComponentModel.IContainer _components = null;

     private static class Win32
     {

        public const uint WM_HSCROLL    = 0x114;
        public const uint WM_VSCROLL    = 0x115;
        public const uint WM_MOUSEWHEEL = 0x20A;
        public const int  SB_VERT       = 0x1;
        public const int  SB_HORZ       = 0x0;

        [System.Runtime.InteropServices.DllImport("user32.dll")]
        public static extern int SetScrollPos
        (  System.IntPtr hWnd
        ,  int nBar
        ,  int nPos
        ,  bool bRedraw
        );
        [System.Runtime.InteropServices.DllImport("user32.dll")]
        public static extern int GetScrollPos
        (  System.IntPtr hWnd
        ,  int nBar
        );

        [  System.Runtime.InteropServices.DllImport
           (  "User32.Dll"
           ,  EntryPoint = "PostMessageA")
        ]
        public static extern bool PostMessage
        (  System.IntPtr hWnd
        ,  uint msg
        ,  int wParam
        ,  int lParam
        );

     }

  }

Answer 3

更好——隐藏MouseWheel事件：https ://stackoverflow.com/a/26672097/1037948

public Form1()
{
    InitializeComponent();
    textBox1.MouseWheel += textBox1_MouseWheel;
}

void textBox1_MouseWheel(object sender, MouseEventArgs e)
{
    throw new NotImplementedException();
}