在移动事件时形成闪烁 [英] form flickers when on move event

问题描述

我编写了以下程序来移动和停靠无边框窗口：

I wrote the following procedure to move and dock a borderless window:

Public Class frmNavigation

    Inherits Form

    'Declarations to allow form movement on mouse down
    Private IsFormBeingDragged As Boolean = False
    Private MouseDownX As Integer
    Private MouseDownY As Integer
    Dim Xs As Integer
    Dim Ys As Integer
    Dim DockScale As Integer

Private Sub frmNavigation_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyBase.MouseDown

        'This procedure allows the user to move the form when the 
        'mouse button is down. The form does not have borders, so it
        'needs to be coded to move.

        If e.Button = MouseButtons.Left Then
            IsFormBeingDragged = True
            MouseDownX = e.X
            MouseDownY = e.Y

        End If
    End Sub

    Private Sub frmNavigation_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyBase.MouseUp

        'This procedure allows the user to move the form when the 
        'mouse button is up. The form does not have borders, so it
        'needs to be coded to move.

        If e.Button = MouseButtons.Left Then
            IsFormBeingDragged = False

        End If
    End Sub

    Private Sub frmNavigation_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyBase.MouseMove

        'This procedure allows the user to move the form when the 
        'mouse button is dragging the form. The form does not have borders, so it
        'needs to be coded to move.

        Dim curScreen As Screen
        curScreen = Screen.PrimaryScreen 'curScreen = Screen.AllScreens(0)
        Dim height As Integer = curScreen.Bounds.Height
        Dim width As Integer = curScreen.Bounds.Width
        width = curScreen.WorkingArea.Width
        height = curScreen.WorkingArea.Height

        If IsFormBeingDragged Then
            Dim temp As System.Drawing.Point = New System.Drawing.Point()

            Xs = MouseDownX
            Ys = MouseDownY

            temp.X = Me.Location.X + (e.X - MouseDownX)
            temp.Y = Me.Location.Y + (e.Y - MouseDownY)
            Me.Location = temp
            temp = Nothing
        End If

End Sub

End Class

到目前为止，这是按设计工作的，它移动表格没有任何问题。当我添加代码以将表单停靠在鼠标移动事件下时，问题就开始了：

So far, this works as designed, it moves the form without any issue whatsoever. The issue starts when I add code to dock the form under the mouse move event as:

Private Sub frmNavigation_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyBase.MouseMove

    'This procedure allows the user to move the form when the 
    'mouse button is dragging the form. The form does not have borders, so it
    'needs to be coded to move.

    Dim curScreen As Screen
    curScreen = Screen.PrimaryScreen 'curScreen = Screen.AllScreens(0)
    Dim height As Integer = curScreen.Bounds.Height
    Dim width As Integer = curScreen.Bounds.Width
    width = curScreen.WorkingArea.Width
    height = curScreen.WorkingArea.Height

    If IsFormBeingDragged Then
        Dim temp As System.Drawing.Point = New System.Drawing.Point()

        Xs = MouseDownX
        Ys = MouseDownY

        temp.X = Me.Location.X + (e.X - MouseDownX)
        temp.Y = Me.Location.Y + (e.Y - MouseDownY)
        Me.Location = temp
        temp = Nothing
    End If

    If IsFormBeingDragged = True And e.Button = MouseButtons.Left Then
        'if the drag flag is true and left mouse button is pressed...

        'set Top side docking
        If Me.Top + (MouseDownY - Ys) < DockScale Then
            Me.Top = 0
            Exit Sub
        End If

        'set bottom side docking
        If Me.Top + (MouseDownY - Ys) + Me.Height > (height - DockScale) Then
            Me.Top = height - Me.Height
            Exit Sub
        End If

        'move the form finally
        Me.Left = Me.Left + (MouseDownX - Xs)
        Me.Top = Me.Top + (e.Y - Ys)
    End If


End Sub

当我添加对接代码并尝试移动表单时，它会移动并停靠，但是当它按住时它会像疯了一样闪烁鼠标向下移动。我不明白为什么会发生这种情况，这是我第一次涉足这样的事情，所以我不确定我哪里出错。

When I add the code for docking and I try to move the form, it moves and it docks, but it flickers like crazy when holding the mouse down and moving. I can't see why this happens, is the first time I dabble with something like this, so I am not sure where I am going wrong.

推荐答案

一个好的防止闪烁的方法是使用双缓冲： http://en.wikipedia.org/wiki/ Double_buffering＃Double_buffering [ ^ ]。 />


以下是您可以使用的属性： http://msdn.microsoft.com/en-us/library/system.windows.forms.control.doublebuffered%28v=vs.110%29.aspx [ ^ ]。



如果你设置if为true，双缓冲将是应用，一切都已经实现。

-SA

A good way to prevent flicker is using double buffering: http://en.wikipedia.org/wiki/Double_buffering#Double_buffering[^].

Here is the property you can use: http://msdn.microsoft.com/en-us/library/system.windows.forms.control.doublebuffered%28v=vs.110%29.aspx[^].

If you set if to true, double buffering will be applied, everything is already implemented for you.

—SA

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