单元格中的VirtualTreeView嵌入按钮

Question

我正在尝试使用TButton创建节点。我创建节点和链接到节点的按钮。在事件TVirtualStringTree.AfterCellPaint上，我初始化按钮上的BoundsRect。但是该按钮始终显示在第一个节点中。

你对这个问题有想法吗？

type
  TNodeData = record
    TextValue: string;
    Button: TButton;
  end;
  PNodeData = ^TNodeData;

procedure TForm1.FormCreate(Sender: TObject);

  procedure AddButton(__Node: PVirtualNode);
  var
    NodeData: PNodeData;
  begin
    NodeData := VirtualStringTree1.GetNodeData(__Node);
    NodeData.Button := TButton.Create(nil);
    with NodeData.Button do
    begin
      Parent := VirtualStringTree1;
      Height := VirtualStringTree1.DefaultNodeHeight;
      Caption := '+';
      Visible := false;
    end;
  end;

  procedure InitializeNodeData(__Node: PVirtualNode; __Text: string);
  var
    NodeData: PNodeData;
  begin
    NodeData := VirtualStringTree1.GetNodeData(__Node);
    NodeData.TextValue := __Text;
  end;

var
  Node: PVirtualNode;
begin
  VirtualStringTree1.NodeDataSize := SizeOf(TNodeData);

  Node := VirtualStringTree1.AddChild(nil);
  InitializeNodeData(Node, 'a');      
  Node := VirtualStringTree1.AddChild(Node);
  InitializeNodeData(Node, 'a.1');

  Node := VirtualStringTree1.AddChild(nil);
  InitializeNodeData(Node, 'b');
  Node := VirtualStringTree1.AddChild(Node);
  InitializeNodeData(Node, 'Here the button');
  AddButton(Node);
end;

procedure TForm1.VirtualStringTree1AfterCellPaint(Sender: TBaseVirtualTree;
  TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex; CellRect: TRect);
var
 NodeData: PNodeData;
begin
  if (Column = 0) then
    Exit;

  NodeData := VirtualStringTree1.GetNodeData(Node);
  if (Assigned(NodeData)) and (Assigned(NodeData.Button)) then
  begin
    with NodeData.Button Do
    begin
      Visible := (vsVisible in Node.States)
                 and ((Node.Parent = VirtualStringTree1.RootNode) or   (vsExpanded in Node.Parent.States));
      BoundsRect := CellRect;
    end;
  end;
end;

Answer 1

OnAfterCellPaint 事件处理程序中 CellRect 参数的坐标是相对于绘制节点的。您需要的是树窗口中节点的绝对位置。您可以通过调用树的 GetDisplayRect 来获取它。所以像这样改变你的代码：

procedure TForm1.VirtualStringTree1AfterCellPaint(Sender: TBaseVirtualTree; TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex; CellRect: TRect);
var
  NodeData: PNodeData;
  R: TRect;
begin
  if (Column = 0) then
    Exit;
  NodeData := VirtualStringTree1.GetNodeData(Node);
  if (Assigned(NodeData)) and (Assigned(NodeData.Button)) then
  begin
    with NodeData.Button Do
    begin
      Visible := (vsVisible in Node.States)
                 and ((Node.Parent = VirtualStringTree1.RootNode) or (vsExpanded in Node.Parent.States));
      R := Sender.GetDisplayRect(Node, Column, False);
      BoundsRect := R;
    end;
  end;
end;