utubform.pas

观察者模式delphi实例实现,同时注意软件的设计

unit uTubForm;

interface

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

type
    TTubForm = class(TForm, IPhotoNotify)
        Panel: TPanel;
        PaintBox: TPaintBox;
        procedure FormDestroy(Sender: TObject);
        procedure FormCreate(Sender: TObject);
        procedure PaintBoxPaint(Sender: TObject);
        procedure PanelResize(Sender: TObject);

    private
        fPhotoMgr: IPhotoMgr;
        fBmp: TBitmap;
        fPID: Integer;

    private
        //实现IPhotoNotify接口
        function SelPhoto(const photoID: Integer): Boolean;
        function NewPhoto(const photoID: Integer): Boolean;
        function DelPhoto(const photoID: Integer): Boolean;
        function Refresh(): Boolean;
        function PropChange(const photoID: Integer): Boolean;

        //显示缩略图
        procedure DrawBmp(bmp:TBitmap;Canvas:TCanvas; aWidth:Integer; aHeight:Integer);

    public
        procedure SetPhotoMgr(aphotoMgr: IPhotoMgr);

    end;

var
    TubForm: TTubForm;

implementation

{$R *.dfm}

{ TTubForm }

procedure TTubForm.FormCreate(Sender: TObject);
begin
    fBmp := TBitmap.Create;
end;

{------------------------------------------------------------------------------}
procedure TTubForm.FormDestroy(Sender: TObject);
begin
    fBmp.Free;
end;

{//////////////////////////////////////////////////////////////////////////////}
function TTubForm.DelPhoto(const photoID: Integer): Boolean;
begin
    Result := True;
    if fPID <> photoID then Exit;
    if fPhotoMgr.GetSelPhotoID(fpid) then
    begin
        fPhotoMgr.GetBmp(fPID,fbmp);
        PaintBox.Invalidate;
    end;
end;

{------------------------------------------------------------------------------}
function TTubForm.NewPhoto(const photoID: Integer): Boolean;
begin
    Result := True;
end;

{------------------------------------------------------------------------------}
function TTubForm.PropChange(const photoID: Integer): Boolean;
begin
    Result := True;
end;

{------------------------------------------------------------------------------}
function TTubForm.Refresh: Boolean;
begin
    Result := True;
    if fPhotoMgr.GetSelPhotoID(fpid) then
    begin
        fPhotoMgr.GetBmp(fPID,fbmp);
        PaintBox.Invalidate;
    end;
end;

{------------------------------------------------------------------------------}
function TTubForm.SelPhoto(const photoID: Integer): Boolean;
begin
    //读取当前选择的照片
    Result := True;
    if fPID = photoID then Exit;
    fPID := photoID;
    fPhotoMgr.GetBmp(fPID,fbmp);
    PaintBox.Invalidate;
end;

{//////////////////////////////////////////////////////////////////////////////}
procedure TTubForm.SetPhotoMgr(aphotoMgr: IPhotoMgr);
begin
    fPhotoMgr := aphotoMgr;
end;

{//////////////////////////////////////////////////////////////////////////////}
//画出缩略图
procedure TTubForm.DrawBmp(bmp: TBitmap; Canvas: TCanvas; aWidth, aHeight: Integer);
var
    nW,nH:Integer;
begin
    //比例调整
    if bmp.Empty then Exit;
//    nW := aHeight * bmp.Width div bmp.Height;
//    nH := aWidth * bmp.Height div bmp.Width;
//    if nW > aWidth then
//    bmp.Canvas.StretchDraw();
end;

{------------------------------------------------------------------------------}
procedure TTubForm.PaintBoxPaint(Sender: TObject);
var
    pt:TPaintBox;
begin
    pt := TPaintBox(Sender);
    DrawBmp(fBmp,pt.Canvas,pt.Width,pt.Height);
end;

{------------------------------------------------------------------------------}
procedure TTubForm.PanelResize(Sender: TObject);
begin
    PaintBox.Invalidate;
end;


end.