Treeview保持滾動位置

Question

我有一個TreeView有很多節點。如果我切換節點，樹視圖的滾動條被設置在底部。

爲了保持切換節點可見，我使用了node.EnsureVisible()。但我不太喜歡這種方法，因爲它讓最終用戶感到困惑。

所以我看得更遠，現在我使用的是這裏提供的代碼：

Maintain scroll position of treeview

這段代碼的問題是，樹視圖的內容不滾動。滾動條位置正確，但內容不起任何作用。直到我點擊滾動條（我不滾動）內容變得可見。

所以，我想要實現的是當treenode被切換時，我想保持滾動位置。

切換節點的代碼。在這種情況下，節點向下。該功能是這樣的：

// Check a node is selected 
if (tvCategories.SelectedNode == null) 
    return; 

// The first node may not be moved 
if (IsNewRootCategorySelected()) 
    return; 

Point ScrollPos = GetTreeViewScrollPos(tvCategories); 

// Declare and instantiate the parent node 
TreeNodeCollection parent = null; 
if (tvCategories.SelectedNode.Parent == null) 
    parent = tvCategories.Nodes; 
else 
    parent = tvCategories.SelectedNode.Parent.Nodes; 

TreeNode selectedNode = tvCategories.SelectedNode; 
int index = selectedNode.Index; 

// Check there's a next node at the same level 
if (tvCategories.SelectedNode.NextNode == null) 
{ 
    // Check if the parent node has a next node 
    if (tvCategories.SelectedNode.Parent != null && tvCategories.SelectedNode.Parent.NextNode != null) 
    { 
     // get the destination parent 
     TreeNode destParent = selectedNode.Parent.NextNode; 

     // remove selected node from tree view 
     parent[index].Remove(); 

     // If selected node is a category, add the node to the first index 
     if (selectedNode.Tag is Category) 
     { 
      destParent.Nodes.Insert(0, selectedNode); 
     } 

     // If selected node is a question, add node below last category 
     if (selectedNode.Tag is Question) 
     { 
      int newIndex = 0; 

      // Loop through collection to find last category 
      for (int i = destParent.Nodes.Count - 1; i >= 0; i--) 
      { 
       if (destParent.Nodes[i].Tag is Category) 
       { 
        newIndex = i + 1; 
        break; 
       } 
      } 

      destParent.Nodes.Insert(newIndex, selectedNode); 
     } 

     selectedNode.Expand(); 
    } 
} 
else 
{ 
    // Switch nodes in same level 

    tvCategories.BeginUpdate(); 
    _loading = true; 

    if (selectedNode.Tag is Category) 
    { 
     // Only switch category downwards when next node is a catgory 
     if (selectedNode.NextNode.Tag is Category) 
     { 
      // Perform switch 
      TreeNode switchNode = parent[index + 1]; 

      parent[index + 1].Remove(); 
      parent[index].Remove(); 

      parent.Insert(index, switchNode); 
      parent.Insert(index + 1, selectedNode); 
     } 
     else if (selectedNode.NextNode.Tag is Question) 
     { 
      // Make the switch to another node below 
      if (selectedNode.Parent.NextNode != null) 
      { 
       // Parent is always a category 

       TreeNode categoryParent = selectedNode.Parent.NextNode; 

       // Remove selected node from current parent 
       parent.Remove(selectedNode); 

       // Insert selected node 
       categoryParent.Nodes.Insert(0, selectedNode); 

      } 
     } 
    } 
    if (selectedNode.Tag is Question) 
    { 
     if (selectedNode.NextNode.Tag is Question) 
     { 
      // Perform switch 
      TreeNode switchNode = parent[index + 1]; 

      parent[index + 1].Remove(); 
      parent[index].Remove(); 

      parent.Insert(index, switchNode); 
      parent.Insert(index + 1, selectedNode); 
     } 
    } 
} 

tvCategories.EndUpdate(); 
// Set focus 
tvCategories.Focus(); 

tvCategories.SelectedNode = selectedNode; 
SetTreeViewScrollPos(tvCategories, ScrollPos); 

Answer 1

using System.Runtime.InteropServices; 

     [DllImport("user32.dll")] 
     static public extern int SendMessage(
       IntPtr hWnd, // HWND handle to destination window 
       int Msg,  // UINT message 
       int wParam, // WPARAM first message parameter 
       int lParam // LPARAM second message parameter 
       ); 

     public const int SB_LINEUP = 0; 
     public const int SB_LINELEFT = 0; 
     public const int SB_LINEDOWN = 1; 
     public const int SB_LINERIGHT = 1; 
     public const int SB_PAGEUP = 2; 
     public const int SB_PAGELEFT = 2; 
     public const int SB_PAGEDOWN = 3; 
     public const int SB_PAGERIGHT = 3; 
     public const int SB_THUMBPOSITION = 4; 
     public const int SB_THUMBTRACK = 5; 
     public const int SB_TOP = 6; 
     public const int SB_LEFT = 6; 
     public const int SB_BOTTOM = 7; 
     public const int SB_RIGHT = 7; 
     public const int SB_ENDSCROLL = 8; 

     public const int WM_HSCROLL = 276; 
     public const int WM_VSCROLL = 277; 

     public void eZScroll(TreeView treeView, ArrowDirection direction, int numScrolls) 
     { 
      int Msg = 0; 
      int wParam = 0; 
      int lParam = 0; 

      switch (direction) 
      { 
       case ArrowDirection.Up: 
        Msg = WM_VSCROLL; 
        wParam = SB_LINEUP; 
        break; 
       case ArrowDirection.Down: 
        Msg = WM_VSCROLL; 
        wParam = SB_LINEDOWN; 
        break; 
       case ArrowDirection.Left: 
        Msg = WM_HSCROLL; 
        wParam = SB_LINELEFT; 
        break; 
       case ArrowDirection.Right: 
        Msg = WM_HSCROLL; 
        wParam = SB_LINERIGHT; 
        break; 
      } 

      for (int i = 0; i < numScrolls; i++) 
      { 
       SendMessage(treeView.Handle, Msg, wParam, lParam); 
      } 
     } 

粘貼的地方後：

public Form1() 
{ 
    InitializeComponent(); 
} 

這樣調用：

eZScroll(treeView1, ArrowDirection.Up, 1); 

我不知道如果這個代碼會工作的時候了但我相信它會讓你很好地解決你的問題。