如何在Memo里实现文本的拖放

问题点数：65、回复次数：1Top

1 楼Bob7946（X度空间）回复于 2001-11-10 11:36:00 得分 65

在Memo里实现文本的拖放  
   
  type  
      TMyMemo   =   class(TMemo)  
      private  
          FLastSelStart     :   Integer;  
          FLastSelLength   :   Integer;  
          procedure   WMLButtonDown(var   Message:   TWMLButtonDown);  
              message   WM_LBUTTONDOWN;  
      published  
          property   LastSelStart   :   Integer   read   FLastSelStart  
              write   FLastSelStart;  
          property   LastSelLength   :   Integer   read   FLastSelLength  
              write   FLastSelLength;  
      end;  
   
  Make   the   implementation   of   WMLButtonDown   look   like   this:  
   
  procedure   TMyMemo.WMLButtonDown(var   Message:   TWMLButtonDown);  
  var  
      Ch:Integer;  
  begin  
      if   SelLength>0   then  
      begin  
          Ch:=LoWord(Perform(EM_CHARFROMPOS,0,MakeLParam(Message.XPos,Message.YPos)));  
          LastSelStart:=SelStart;  
          LastSelLength:=SelLength;  
          if   (Ch>=SelStart)   and   (Ch<=SelStart+SelLength-1)   then  
              BeginDrag(True)  
          else  
              inherited;  
      end  
      else  
          inherited;  
  end;  
   
  Now,   install   this   component   into   a   package,   start   a   brand   new   project  
  in   Delphi   3   and   drop   two   TMyMemos   down.  
   
  Make   them   both   have   an   OnDragOver   event   handler   looking   like   this:  
   
  procedure   TForm1.MyMemo1DragOver(Sender,Source:TObject;X,Y:Integer;State:TDragState;var   Accept:Boolean);  
  begin  
      Accept:=Source   is   TMyMemo;  
  end;  
   
  Make   them   both   have   an   OnDragDrop   event   handler   looking   like   this:  
   
  procedure   TForm1.MyMemo1DragDrop(Sender,   Source:   TObject;X,Y:Integer);  
  var  
      Dst,Src:TMyMemo;  
      Ch           :Integer;  
      Temp       :String;  
  begin  
      Dst:=SenderasTMyMemo;  
      Src:=SourceasTMyMemo;  
      Ch:=LoWord(Dst.Perform(EM_CHARFROMPOS,0,MakeLParam(X,Y)));  
      if   (Src=Dst)   and   (Ch>=Src.LastSelStart)   and   (Ch<=Src.LastSelStart+Src.LastSelLength-1)   then  
          Exit;  
      Dst.Text:=Copy(Dst.Text,1,Ch)+Src.SelText+Copy(Dst.Text,Ch+1,Length(Dst.Text)-Ch);  
      Temp:=Src.Text;  
      Delete(Temp,Src.LastSelStart+1,Src.LastSelLength);  
      Src.Text:=Temp;  
  end;Top

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