关于动画移动矩形的例子 - 回复

​​ 关于动画移动矩形的例子 - 回复 "ps8.0" 同学 ​​

问题来源:​​https://blog.51cto.com/u_14617575/2835198​​

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首先, 实现这个问题有两种方法:

1、边擦边画; 2、先在内存绘图然后再复制到前台, 就是所谓的双倍缓存.

本例使用的是比较传统的 "边擦边画" 法, 但现在更提倡使用 "双倍缓存" 法.

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本例效果图(实际的动画效果比这个 gif 要好一些):

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代码文件:

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unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Timer1: TTimer;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  pt1,pt2: TPoint;  {两个点}
  n: Integer = 20;  {用于正方形大小}
  cvs: TCanvas;     {画布}
  a,b,ai,bi: Single;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Timer1.Enabled := False;
  Timer1.Interval := 25;

  Button1.Caption := '画正方形';
  Button2.Caption := '移动';
  Button3.Caption := '暂停';

  cvs := TCanvas.Create;
  cvs.Handle := GetDC(Handle);

  Self.Color := clWhite;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  {给两个点赋值}
  pt1.X := 30;
  pt1.Y := 30;
  pt2.X := ClientWidth - 30;
  pt2.Y := ClientHeight - 30;

  {记下起始点的位置}
  a := pt1.X;
  b := pt1.Y;

  {算出每次的偏移量}
  ai := (pt2.X-pt1.X)/100; {假如用 100 次移动完毕}
  bi := (pt2.Y-pt1.Y)/100;

  {在第一点位置画出矩形, 使用随机颜色}
  Randomize;
  cvs.Pen.Color := Random($FFFFFF);
  cvs.Pen.Width := 4;
  cvs.Rectangle(Round(a-n), Round(b-n), Round(a+n), Round(b+n));
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Timer1.Enabled := True;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  Timer1.Enabled := False;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  if a >= pt2.X then
  begin
    Timer1.Enabled := False;
    Exit;
  end;

  {擦除上一个}
  cvs.Pen.Mode := pmNotXor;
  cvs.Rectangle(Round(a-n), Round(b-n), Round(a+n), Round(b+n));

  {再画}
  cvs.Pen.Mode := pmCopy;
  a := a+ai;
  b := b+bi;
  cvs.Rectangle(Round(a-n), Round(b-n), Round(a+n), Round(b+n));
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  cvs.Free;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 214
  ClientWidth = 335
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 252
    Top = 8
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 252
    Top = 39
    Width = 75
    Height = 25
    Caption = 'Button2'
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 252
    Top = 70
    Width = 75
    Height = 25
    Caption = 'Button3'
    TabOrder = 2
    OnClick = Button3Click
  end
  object Timer1: TTimer
    OnTimer = Timer1Timer
    Left = 168
    Top = 80
  end
end