Question

尝试在ListView控件中实现撤消/重做操作时遇到太多问题，只是为了添加/删除项目。

我很久以前就意识到这里有一个相对的问题Extend this Class to Undo/Redo in a Listview我开始了50分，100分，200分和300分的多个分数，共计650分......但是没有任何身体可以真正帮助我完成这个几周和几个月的问题。

但是经过一段时间后，一个用户（@ThorstenC）向我展示了一个可能的解决方案和一个好主意，他的代码是不完整的，所以他的代码就是我想要实现/完成的。

问题是简单的“撤销”工作正常，但是当我尝试重做超过1次时它抛出一个异常，它不能在listview中再次添加相同的项目，代码也有更多的问题，例如在我无法重做撤消操作或撤消重做操作的那一刻。

我需要帮助才能为Listview项目添加/删除创建一个有效的Undo / Redo管理器，就是这样，我已经编写了代码的一半部分，我需要帮助才能完成它我脑子里有一个乱七八糟的东西

这是VS2012中的一个简单的WinForms源项目，我上传以测试撤消管理器失败：

http://elektrostudios.tk/UndoManager.zip

enter image description here

这是一段视频，向您展示我尝试撤消/重做的错误：http://www.youtube.com/watch?v=MAzChURATpM

这是@ThorstenC的UndoManager类，有一点点修饰：

Class ListView_UndoManager

    Public Property Undostack As New Stack(Of ListView_Action)
    Public Property Redostack As New Stack(Of ListView_Action)

    Public Property IsDoingUndo As Boolean ' = False
    Public Property IsDoingRedo As Boolean ' = False

    Private action As ListView_Action = Nothing

    ''' <summary>
    ''' Undo the last action.
    ''' </summary>
    ''' <remarks></remarks>
    Sub UndoLastAction()

        If Undostack.Count = 0 Then Exit Sub ' Nothing to Undo.

        action = Undostack.Pop ' Get the Action from Stack and remove it.
        action.Operation.DynamicInvoke(action.data) ' Invoke the undo Action.

        'Redostack = New Stack(Of ListView_Action)(Redostack)
        'Redostack.Pop()
        'Redostack = New Stack(Of ListView_Action)(Redostack)

    End Sub

    ''' <summary>
    ''' Redo the last action.
    ''' </summary>
    ''' <remarks></remarks>
    Sub RedoLastAction()

        ' If Redostack.Count = Undostack.Count Then Exit Sub

        If Redostack.Count = 0 Then Exit Sub ' Nothing to Redo.

        'Redostack = New Stack(Of ListView_Action)(Redostack) ' Reverse the Stack contents.

        action = Redostack.Pop() ' Get the Action from Stack and remove it.
        ' action = Redostack.Peek()

         action.Operation.DynamicInvoke(action.data) ' Invoke the redo Action.

        'Redostack = New Stack(Of ListView_Action)(Redostack) ' Re-Reverse the Stack contents.

    End Sub

End Class

Class ListView_Action

    ''' <summary>
    ''' Name the Undo / Redo Action
    ''' </summary>
    ''' <value></value>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Property name As String

    ''' <summary>
    ''' Points to a method to excecute
    ''' </summary>
    ''' <value></value>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Property Operation As [Delegate]

    ''' <summary>
    ''' Data Array for the method to excecute
    ''' </summary>
    ''' <value></value>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Property data As Object()

End Class

以下是我正在尝试撤消/重做添加/删除listview项目的其余代码：

Public Class Form1


    Dim _undoManager As New ListView_UndoManager
    Delegate Sub RemoveDelegate(item As ListViewItem)
    Delegate Sub AddDelegate(item As ListViewItem)

    Dim newItem As ListViewItem = Nothing



    Sub AddItem(ByVal item As ListViewItem)

        ' // Crate an Undo Action
        Dim u As New ListView_Action() With {.name = "Remove Item",
                            .Operation = New RemoveDelegate(AddressOf RemoveItem),
                                    .data = New Object() {newItem}}

        _undoManager.Undostack.Push(u)

        ListView_Elektro1.AddItem(item)

    End Sub

    Sub RemoveItem(item As ListViewItem)

        ' // Create a Redo Action
        Dim r As New ListView_Action() With {.name = "Add Item",
                    .Operation = New AddDelegate(AddressOf AddItem),
                            .data = New Object() {item}}

        _undoManager.Redostack.Push(r)

        ' Remove the ListViewItem from ListView
        ListView_Elektro1.RemoveItem(item)

    End Sub

    Private Sub Button_AddItem_Click(sender As Object, e As EventArgs) _
    Handles Button_AddItem.Click

        Dim index As String = CStr(ListView_Elektro1.Items.Count + 1)

        newItem = New ListViewItem _
                  With {.Text = index}
        newItem.SubItems.AddRange({"Hello " & index, "World " & index})

        AddItem(newItem)

    End Sub

    Private Sub Button_RemoveItem_Click(sender As Object, e As EventArgs) _
    Handles Button_RemoveItem.Click

        newItem = ListView_Elektro1.Items.Cast(Of ListViewItem).Last

        RemoveItem(newItem)

    End Sub

    Private Sub Button_Undo_Click(sender As Object, e As EventArgs) _
    Handles Button_Undo.Click

        ' _undoManager.IsDoingUndo = True
        _undoManager.UndoLastAction()
        ' _undoManager.IsDoingUndo = False

    End Sub

    Private Sub Button_Redo_Click(sender As Object, e As EventArgs) _
    Handles Button_Redo.Click

        '_undoManager.IsDoingRedo = True
        _undoManager.RedoLastAction()
        '_undoManager.IsDoingRedo = False

    End Sub

    Private Sub ListView_Elektro1_ItemAdded() _
    Handles ListView_Elektro1.ItemAdded, _
            ListView_Elektro1.ItemRemoved

        Label_UndoCount_Value.Text = CStr(_undoManager.Undostack.Count)
        Label_RedoCount_Value.Text = CStr(_undoManager.Redostack.Count)

    End Sub

End Class

Answer 1

“El URL requerido no fue encontrado en este servidor。”所以我很确定这就是它：

action = Redostack.Peek() ' Get the Action from Stack and remove it.

不，你正在看没有从堆栈中获取它。原作和快速返工都是我用过的：

action = Redostack.Pop()

由于您正在堆叠中存储实际的LV项目以回发给LV，第二次按下它时，您正在查看并尝试恢复已经在LV中的一个。

由于大多数原始“命令”将Undo / ReDo数据保存为对象，为什么你只是在UnDoReDoManager上公开AddLVUndoItem(item)以使用现有代码将LV动作与其他控件集成？它的问题是没有LVItemAdded事件来自动抓取这些东西。将此作为用户控制功能与另一个一起使用的一个问题是，您现在有2个堆栈，一个跳过LV，另一个只执行LV。用户可以清空另一个堆栈，试图进行LV撤消操作。

此外，添加项目属于UnDo存储桶，但不属于RemoveItem，反之亦然，适用于RemoveItem（无法撤消RemoveItem）。在原始撤消中自动将命令添加到ReDo堆栈。它在标题和旧请求中，但不在代码中。

修改这是错的：

Sub RemoveItem(item As ListViewItem) ' // Create a Redo Action Dim r As New ListView_Action() With {.name = "Add Item", .Operation = New AddDelegate(AddressOf AddItem), .data = New Object() {item}} ' wrong! _undoManager.Redostack.Push(r) ' Remove the ListViewItem from ListView ListView_Elektro1.RemoveItem(item) End Sub

你没有为undoStack创建一个新的LVI，使用传递的那个删除的那个（回想一下我必须改变我的VS ver的语法）：

Sub RemoveItem(ByVal item As ListViewItem) ' // Create a Redo Action Dim r As New ListView_Action() With r .name = "Add Item" .Operation = New AddDelegate(AddressOf AddItem) .data = item ' use the one passed!!! End With _undoManager.Redostack.Push(r) ' Remove the ListViewItem from ListView LVE.RemoveItem(item) _undoManager.ShowStacks() End Sub

因此，您的ReDo没有缓存任何UnDo操作。它看起来只是由于人工测试数据。

Answer 2

您可能还想查看用VB.NET编写的这个撤销/重做框架

http://www.codeproject.com/Articles/43436/Undo-Redo-Framework

它专为以下类型的控件而设计（但大多数情况下也应该使用自定义控件）

TextBox
ComboBox
DateTimePicker
NumericUpDown
MaskedTextBox
ListBox（单选和多选）
CheckBox
RadioButton
MonthCalendar
ListView（标签文字更改）

实现添加/删除ListView项的撤消/重做操作

2 个答案: