如何接受拖放文件

　　在Delphi中接受拖放並不難，只要在FormCreate說明一下，然後處理WM_DROPFILES就可以了，以下是簡單的例子。

Type
  tFiles = array of string;
  TForm1 = class(TForm)
  ...
  private
    procedure OnAcceptfiles(Sender: tobject; var Files: tFiles);
    procedure AcceptFiles(var msg : TMessage); message WM_DROPFILES;
    ...
  end;

...

implementation

uses
  ShellAPI;

procedure TForm1.FormCreate(Sender: TObject);
begin
  DragAcceptFiles(Handle, True);
end;

procedure TPoemForm.AcceptFiles(var msg: TMessage);
const
  cnMaxFileNameLen = 255;
var
  i, n: integer;
  acFileName: array [0..cnMaxFileNameLen] of char;
  Files: tFiles;
begin
  // 首先求得檔案數目
  n:=DragQueryFile(msg.WParam, $FFFFFFFF, acFileName, cnMaxFileNameLen);
  Setlength(Files, n);
  try
    // 遂一求得檔案名
    for i:=0 to n-1 do
    begin
      DragQueryFile(msg.WParam, i, acFileName, cnMaxFileNameLen);
      Files[i]:=acFileName;
    end;
  finally
    // 結束拖放處理
    DragFinish(msg.WParam);
  end;
  if n>0 then 
    OnAcceptfiles(Self, Files);
end;

procedure TPoemForm.OnAcceptfiles(Sender: tobject; var Files: tFiles);
begin
  // 做想做的事
end;

....

end.

　　上面例子中整個Form都可接受拖放文件，如果想只要Form的一部分接受文件，改變DragAcceptFiles所用的Handle即可，也可以多次使用DragAcceptFiles，使得多個控制元件接受拖放。

閱讀全文......

打印機的大小及分辨率

　　使用GetDeviceCaps可以求得各種設備的大小，以下把它做成了OBJECT，方便使用：

interface

uses
  windows，Classes;

type
  TDeviceCaps=class
  private
    fHandle: tHandle;
    function GetCapabilities(i: integer): integer;
  public
    constructor Create(h: thandle);
    property Handle: tHandle read fHandle write fHandle;
    property Capabilities[i: integer]: integer read GetCapabilities;
    property Driver_Version: integer index windows.DRIVERVERSION read GetCapabilities;
    property Technology: integer index windows.TECHNOLOGY read GetCapabilities;
    property X_SizeMM: integer index windows.HORZSIZE read GetCapabilities;            // in mm
    property Y_SizeMM: integer index windows.VERTSIZE read GetCapabilities;
    property X_Size: integer index windows.HORZRES read GetCapabilities;       // in pixels
    property Y_Size: integer index windows.VERTRES read GetCapabilities;
    property X_LogPixel: integer index windows.LOGPIXELSX read GetCapabilities;      // in dpi
    property Y_LogPixel: integer index windows.LOGPIXELSY read GetCapabilities;
    property X_PhysicalSize: integer index windows.PHYSICALWIDTH read GetCapabilities;   // in pixels
    property Y_PhysicalSize: integer index windows.PHYSICALHEIGHT read GetCapabilities;
    property X_PhysicalOffset: integer index windows.PHYSICALOFFSETX read GetCapabilities;   // in pixels
    property Y_PhysicalOffset: integer index windows.PHYSICALOFFSETY read GetCapabilities;
  end;

implementation

constructor TDeviceCaps.Create(h: thandle);
begin
  fHandle:=h;
end;

function TDeviceCaps.GetCapabilities(i: integer): integer;
begin
  result:=GetDeviceCaps(fHandle,i);
end;

使用方法如下：

var
  PrinterDev: tDeviceCaps;

....
  PrinterDev:=tDeviceCaps.Create(printer.handle);
  Xdpi    :=PrinterDev.X_LogPixel;
....

閱讀全文......

關於任務欄

　　想知道Taskbar是否可見，或者想隱藏它，可以用以下Windows API：

function IsTaskBarVisible: boolean;
var
  wndHandle : THandle;
  wndClass  : array[0..50] of Char;
begin
  StrPCopy(@wndClass[0], 'Shell_TrayWnd');
  wndHandle := FindWindow(@wndClass[0], nil);
  result := ShowWindow(wndHandle, SW_SHOWNA);
end;

procedure HideTaskBar;
var
  wndHandle : THandle;
  wndClass  : array[0..50] of Char;
begin
 StrPCopy(@wndClass[0], 'Shell_TrayWnd');
 wndHandle := FindWindow(@wndClass[0], nil);
 ShowWindow(wndHandle, SW_HIDE);
end;

procedure ShowTaskBar;
var wndHandle : THandle;
  wndClass  : array[0..50] of Char;
begin
 StrPCopy(@wndClass[0], 'Shell_TrayWnd');
 wndHandle := FindWindow(@wndClass[0], nil);
 ShowWindow(wndHandle, SW_RESTORE);
end;

閱讀全文......