VCL 中的 Windows API 函数: BeginDeferWindowPos

BeginDeferWindowPos 和 DeferWindowPos、EndDeferWindowPos 是一组一起使用的函数, 可对一组窗口的位置、大小、Z 序等进行调整, 在 ExtCtrls 单元有用到.

---

下面先用常规方法实现对 Panel1 中的一组 Button 进行调整, 然后再用上面三个函数重新实现.

---

用 BeginDeferWindowPos、DeferWindowPos、EndDeferWindowPos 重新实现的代码(窗体和运行效果是一样的):

---

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    RadioButton1: TRadioButton;
    RadioButton2: TRadioButton;
    procedure RadioButton1Click(Sender: TObject);
    procedure RadioButton2Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.RadioButton1Click(Sender: TObject);
var
  num,i: Integer;
  btn: TButton;
  L,T,W,H: Integer;
  DeferHandle: THandle;
begin
  num := Panel1.ControlCount;

  L := 10;
  T := 10;
  W := (Panel1.ClientWidth - L * (num+1)) div num;
  H := (Panel1.ClientHeight - T * (num+1)) div num;

  DeferHandle := BeginDeferWindowPos(num); {准备调整一组窗口}
  for i := 0 to num - 1 do
  begin
    if Panel1.Controls[i] is TButton then
    begin
      btn := TButton(Panel1.Controls[i]);
      DeferHandle := DeferWindowPos(DeferHandle,
                                    btn.Handle,
                                    HWND_TOP,                 {此参数决定 Z 序}
                                    L, (H + T) * i + T, W, H, {新的位置与大小}
                                    SWP_NOZORDER              {更多控制, 现在是不改变 Z 序}
                                    );
    end;
  end;
  EndDeferWindowPos(DeferHandle); {实施调整}
end;

procedure TForm1.RadioButton2Click(Sender: TObject);
var
  num,i: Integer;
  btn: TButton;
  L,T,W,H: Integer;
  DeferHandle: THandle;
begin
  num := Panel1.ControlCount;

  L := 10;
  T := 10;
  W := (Panel1.ClientWidth - L * (num+1)) div num;
  H := (Panel1.ClientHeight - T * (num+1)) div num;

  DeferHandle := BeginDeferWindowPos(num);
  for i := 0 to num - 1 do
  begin
    if Panel1.Controls[i] is TButton then
    begin
      btn := TButton(Panel1.Controls[i]);
      DeferHandle := DeferWindowPos(DeferHandle,
                                    btn.Handle,
                                    HWND_TOP,
                                    (W + L) * i + L, T, W, H,
                                    SWP_NOZORDER
                                    );
    end;
  end;
  EndDeferWindowPos(DeferHandle);
end;

end.