delphi - 根据拖动区域动态调整控件大小

Question

我有一个表格，左边有一个 TTreeview，右边有一个 TGroupbox。当通过拖动右边缘来调整表单大小时，我希望 Groupbox 相应地增长或缩小。当表单被拖动到左侧时，我希望 Treeview 调整大小。我尝试了下面的代码并且正确调整大小工作正常。但是左调整大小会导致 TreeView 增长得比它应该的长。实现这一目标的正确方法是什么？

procedure TForm1.FormResize(Sender: TObject);
var
  p: TPoint;
begin
  P:= ScreenToClient(Mouse.CursorPos);
  if(P.X<0) then begin
    Treeview1.Anchors:= [akLeft,akTop,akRight,akBottom];
    Groupbox1.Anchors:= [akTop,akBottom];
  end
  else begin
    Treeview1.Anchors:= [akLeft,akTop,akBottom];
    Groupbox1.Anchors:= [akLeft,akTop,akRight,akBottom];
  end;
end;

Answer 1

而不是处理 OnResize事件，您可以改为拦截 WM_SIZING 改为消息

Sent to a window that the user is resizing. By processing this message, an application can monitor the size and position of the drag rectangle and, if needed, change its size or position.

其 wParam value 准确地告诉您正在调整窗口的哪些边缘。您可以使用它来调整 Anchors因此，例如:

type
  TForm1 = class(TForm)
    TreeView1: TTreeView;
    GroupBox1: TGroupBox;
  private
    { Private declarations }
    procedure WMSizing(var Message: TMessage); message WM_SIZING;
  public
    { Public declarations }
  end;

...

procedure TForm1.WMSizing(var Message: TMessage);
var
  TreeViewAnchors: TAnchors;
  GroupBoxAnchors: TAnchors;
begin
  inherited;

  TreeViewAnchors := [akTop, akBottom];
  GroupBoxAnchors := [akTop, akBottom];

  case Message.WParam of
    WMSZ_LEFT, WMSZ_BOTTOMLEFT, WMSZ_TOPLEFT: begin
      TreeViewAnchors := TreeViewAnchors + [akLeft, akRight];
      GroupBoxAnchors := GroupBoxAnchors + [akRight];
    end;
    WMSZ_RIGHT, WMSZ_BOTTOMRIGHT, WMSZ_TOPRIGHT: begin
      TreeViewAnchors := TreeViewAnchors + [akLeft];
      GroupBoxAnchors := GroupBoxAnchors + [akLeft, akRight];
    end;
  end;

  TreeView1.Anchors := TreeViewAnchors;
  GroupBox1.Anchors := GroupBoxAnchors;
end;