unit Unit1;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.Layouts, FMX.Memo;

type
  TForm1 = class(TForm)
    Memo1: TMemo; //先在空白窗体上放 Memo1
  private
  public
    { 覆盖这个两个方法 }
    procedure DragOver(const Data: TDragObject; const Point: TPointF; var Accept: Boolean); override;
    procedure DragDrop(const Data: TDragObject; const Point: TPointF); override;
  end;

var
  Form1: TForm1;

implementation

{$R *.fmx}

{ TForm1 }

procedure TForm1.DragOver(const Data: TDragObject; const Point: TPointF; var Accept: Boolean);
begin
  inherited;
  { 如果拖拽的是文件, 且是 *.txt 文件, 则让 Accept := True 以让后面的 DragDrop 事件响应 }
  Accept := (Length(Data.Files) > 0) and (CompareText(ExtractFileExt(Data.Files[0]), '.txt') = 0);
end;

procedure TForm1.DragDrop(const Data: TDragObject; const Point: TPointF);
begin
  inherited;
  Memo1.Lines.LoadFromFile(Data.Files[0]);
end;

end.