编写Flat风格的Button

本文主要是介绍编写Flat风格的Button，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

Delphi标准的组件中的Button组件都是3D风格的组件，即使像SpeedButton组件具有Flat属性，但是确没有了Border。因此我们需要一个简单功能的Flat风格组件又不想使用第三方组件，该怎么办呢？通过阅读delphi源代码和反复尝试，我们发现组件的风格主要通过重载    procedure CreateParams(var Params: TCreateParams); override;方法来实现，这也是delphi组件和windows标准组件结合的位置。我们看一下源代码：
procedure TButton.CreateParams(var Params: TCreateParams);
const
ButtonStyles: array[Boolean] of DWORD = (BS_PUSHBUTTON, BS_DEFPUSHBUTTON);
begin
inherited CreateParams(Params); //继承祖先的方法
CreateSubClass(Params, 'BUTTON'); //创建windows组件button类
Params.Style := Params.Style or ButtonStyles[FDefault]; //设置button类型
end;
我们继续跟踪发现ButtonStyles控制了他的border外观，同时由FDefault来确定。我们继续跟踪，就来到了Windows单元，组件风格的秘密就全在这里了。我们来看看：
BS_PUSHBUTTON,
BS_DEFPUSHBUTTON
通过字面意思不难理解，BS_FLAT就是我们要找的。好了，接下来我们实现它就OK了。
代码及测试代码实现如下：
unit Unit1;

interface

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

type
TFlatButton = class(TButtonControl)
private
    FCancel: Boolean;
    FDefault: Boolean;
    FActive: Boolean;
    FModalResult: TModalResult;
    procedure SetDefault(const Value: Boolean);
    procedure CNCtlColorBtn(var Message: TWMCtlColorBtn); message CN_CTLCOLORBTN;
    procedure WMEraseBkgnd(var Message: TWMEraseBkgnd); message WM_ERASEBKGND;
protected
    procedure CreateParams(var Params: TCreateParams); override;
    procedure CreateWnd; override;
public
    constructor Create(AOwner: TComponent); override;
    procedure Click; override;
    function UseRightToLeftAlignment: Boolean; override;
published
    property Action;
    property Anchors;
    property BiDiMode;
    property Cancel: Boolean read FCancel write FCancel default False;
    property Caption;
    property Constraints;
    property Default: Boolean read FDefault write SetDefault default False;
    property DragCursor;
    property DragKind;
    property DragMode;
    property Enabled;
    property Font;
    property ModalResult: TModalResult read FModalResult write FModalResult default 0;
    property ParentBiDiMode;
    property ParentFont;
    property ParentShowHint;
    property PopupMenu;
    property ShowHint;
    property TabOrder;
    property TabStop default True;
    property Visible;
    property WordWrap;
    property OnClick;
    property OnContextPopup;
    property OnDragDrop;
    property OnDragOver;
    property OnEndDock;
    property OnEndDrag;
    property OnEnter;
    property OnExit;
    property OnKeyDown;
    property OnKeyPress;
    property OnKeyUp;
    property OnMouseDown;
    property OnMouseMove;
    property OnMouseUp;
    property OnStartDock;
    property OnStartDrag;
end;

TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
private
    { Private declarations }
public
    procedure MyClick(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

{ TFlatButton }

procedure TFlatButton.Click;
var
Form: TCustomForm;
begin
Form := GetParentForm(Self);
if Form <> nil then Form.ModalResult := ModalResult;
inherited Click;
end;

procedure TFlatButton.CNCtlColorBtn(var Message: TWMCtlColorBtn);
begin
with ThemeServices do
    if ThemesEnabled then
    begin
      DrawParentBackground(Handle, Message.ChildDC, nil, False);
      { Return an empty brush to prevent Windows from overpainting we just have created. }
      Message.Result := GetStockObject(NULL_BRUSH);
    end
    else
      inherited;
end;

constructor TFlatButton.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
Width := 75;
Height := 25;
TabStop := True;
end;

procedure TFlatButton.CreateParams(var Params: TCreateParams);
const
ButtonStyles: array[Boolean] of DWORD = (BS_FLAT, BS_DEFPUSHBUTTON);
begin
inherited CreateParams(Params);
CreateSubClass(Params, 'BUTTON');
Params.Style := Params.Style or BS_FLAT;//ButtonStyles[FDefault];
end;

procedure TFlatButton.CreateWnd;
begin
inherited CreateWnd;
FActive := FDefault;
end;

procedure TFlatButton.SetDefault(const Value: Boolean);
begin
FDefault := Value;
end;

function TFlatButton.UseRightToLeftAlignment: Boolean;
begin
Result := False;
end;

procedure TFlatButton.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
if ThemeServices.ThemesEnabled then
    Message.Result := 1
else
    DefaultHandler(Message);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
button: TFlatButton;
begin
button := TFlatButton.Create(self);
button.Parent := self;
button.Caption := '&OK';
button.SetBounds(10, 10, 75, 25);
button.OnClick := myClick;
end;

procedure TForm1.MyClick(Sender: TObject);
begin
showmessage('you clicked me!');
end;

end.