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Jakub Sluka's questions

Martin Hope
Jakub Sluka
Asked: 2024-10-12 00:00:10 +0800 CST
  • 5

我正在学习 Delphi，当我调用执行逻辑的私有函数时，无法显示对话框。它看起来像是一个空指针引用，但我找不到它在哪里。

图像

以下是代码：

unit SandBox;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    AhojButton: TButton;
    procedure AhojButtonClick(Sender: TObject);

  private
    procedure ShowDialog(amount: Integer);

  public

  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.ShowDialog(amount: Integer);

  var td: TTaskDialog;
  var tb: TTaskDialogBaseButtonItem;
begin

  try
    td := TTaskDialog.Create(nil);
    tb := TTaskDialogBaseButtonItem.Create(nil);

    td.Caption := 'Warning';
    td.Text := 'Continue or Close?';
    td.MainIcon := tdiWarning;
    td.CommonButtons := [];

    tb := td.Buttons.Add;
    tb.Caption := 'Continue';
    tb.ModalResult := 100;

    tb := td.Buttons.Add;
    tb.Caption := 'Close';
    tb.ModalResult := 101;

    td.Execute;

    if td.ModalResult = 100 then
      ShowMessage('Continue')
    else if td.ModalResult = 101 then
      ShowMessage('Close');

  finally
    td.Free;
    tb.Free;
  end;

end;

procedure TForm1.AhojButtonClick(Sender: TObject);
begin
  ShowDialog(100);
end;

end.

我试图实例化并释放TTaskDialog和TTaskDialogBaseButtonItem。

此行引发错误：

tb := TTaskDialogBaseButtonItem.Create(nil);
delphi