API - SetCapture(),ReleaseCapture与GetCapture - 鼠标移动的捕获与释放

演示效果:

添加控件:Form1,Button1,Label1,Label2,Timer1

GetCapture:返回当前捕获鼠标输入的窗口的句柄
SetCapture():通过句柄设置指定窗口来捕获鼠标的输入
ReleaseCapture:释放当前捕获鼠标的窗口的捕获功能
同一时间只能有一个前景窗口可以捕获鼠标。当在控件上按下鼠标时，会自动执行SetCapture()，这时该控件的鼠标移动事件在全屏都会触发，松开鼠标按键时自动执行ReleaseCapture释放捕获

代码文件:

 

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Label1: TLabel;
    Label2: TLabel;
    Timer1: TTimer;
    procedure Timer1Timer(Sender: TObject);
    procedure Button1MouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  if GetCapture=Button1.Handle then
    Label2.Caption:='Get'
  else
    Label2.Caption:='Release'
end;

procedure TForm1.Button1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  Label1.Caption:=Format('%d,%d',[x,y]);
end;

end.

窗体文件:

object Form1: TForm1
  Left = 412
  Top = 202
  Width = 262
  Height = 164
  Caption = 'Form1'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Label1: TLabel
    Left = 16
    Top = 8
    Width = 24
    Height = 13
    Caption = '坐标'
  end
  object Label2: TLabel
    Left = 16
    Top = 32
    Width = 32
    Height = 13
    Caption = 'Label2'
  end
  object Button1: TButton
    Left = 16
    Top = 56
    Width = 75
    Height = 57
    Caption = 'Button1'
    TabOrder = 0
    OnMouseMove = Button1MouseMove
  end
  object Timer1: TTimer
    Interval = 100
    OnTimer = Timer1Timer
    Left = 208
    Top = 8
  end
end