如何在VB.NET中跟踪鼠标单击和拖动事件？

Question

First, I want to know if the mouse is in some area. Then, I want to check if the mouse holds the left click. I want to check as long as the left button is down, and I want to track the mouse's position. And finally, check when the left button is released.

So, in short, where should I start for tracking mouse events in my form?

Answer 1

This is a simple code for detect Drag or Click

Public IsDragging As Boolean = False, IsClick As Boolean = False
Public StartPoint, FirstPoint, LastPoint As Point
Private Sub PictureBox1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles picBook.Click
    If IsClick = True Then MsgBox("CLick")
End Sub

Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picBook.MouseDown
    StartPoint = picBook.PointToScreen(New Point(e.X, e.Y))
    FirstPoint = StartPoint
    IsDragging = True
End Sub

Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picBook.MouseMove
    If IsDragging Then
        Dim EndPoint As Point = picBook.PointToScreen(New Point(e.X, e.Y))
        IsClick = False
        picBook.Left += (EndPoint.X - StartPoint.X)
        picBook.Top += (EndPoint.Y - StartPoint.Y)
        StartPoint = EndPoint
        LastPoint = EndPoint
    End If
End Sub

Private Sub PictureBox1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picBook.MouseUp
    IsDragging = False
    If LastPoint = StartPoint Then IsClick = True Else IsClick = False
End Sub

Answer 2

Generally speaking, when the mouse down event occurs, you would need to capture the mouse. Then you will receive mouse move events even if the mouse leaves the area of the control that has captured the mouse. You can calculate delta's in the mouse move events. A drag would occur the first time the delta exceeds a system-defined "drag area". When the mouse up event is received, stop the drag operation.

In Windows Forms, look at the MouseDown, MouseMove, and MouseUp events on the Control class. The MouseEventArgs will contain the X/Y coordinates. To capture or release the mouse, set the Capture property to true or false respectively. If you do not capture the mouse, then you will not receive the MouseMove or MouseUp events if the mouse is released outside of the bounds of the control.

Finally, to determine the minimum "distance" the mouse should be allowed to move before starting the drag operation, look at the SystemInformation.DragSize property.

Hope this helps.

Answer 3

Understandably this is old, but I ran across this post while looking to do the same thing. I thought there might be an actual drag event, but I guess not. Here's how I did it.

Private Sub ContainerToolStripMenuItem_Click(sender As System.Object, e As System.EventArgs) Handles ContainerToolStripMenuItem.Click
    Dim pnl As New Panel
    pnl.Size = New Size(160, 160)
    pnl.BackColor = Color.White
    AddHandler pnl.MouseDown, AddressOf Control_DragEnter
    AddHandler pnl.MouseUp, AddressOf Control_DragLeave
    AddHandler pnl.MouseMove, AddressOf Control_Move
    Me.Controls.Add(pnl)
End Sub

Private Sub Control_DragEnter(ByVal sender As Object, ByVal e As EventArgs)
    MouseDragging = True
End Sub

Private Sub Control_DragLeave(ByVal sender As Object, ByVal e As EventArgs)
    MouseDragging = False
End Sub

Private Sub Control_Move(ByVal sender As Object, ByVal e As EventArgs)
    If MouseDragging = True Then
        sender.Location = Me.PointToClient(Control.MousePosition)
    End If
End Sub

The ContainerToolStripMenuItem is from my ToolStrip that adds a Panel on-the-fly. MouseDragging is class level. Drags like a charm. Also, don't use Cursor.Position as it will return the position relative to your entire Window, not the Form (or whatever container it is you're in).

Answer 4

The only way to go about doing this is via javascript.

This article will explain it to you. http://luke.breuer.com/tutorial/javascript-drag-and-drop-tutorial.aspx