表单上的Delphi访问冲突显示

Question

很抱歉不得不打开新问题,但我无法在任何地方找到答案.

我的应用程序仍在进行中,但基本上我在初始化播放器时尝试从我的MainForm调用另一个Form,但是我收到了Access Violation错误.你能否向我解释为什么会发生这种情况？

我的MainForm代码:

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, Buttons, ExtCtrls, jpeg, pngimage, getPlayer_u;...

procedure TfrmMain.FormCreate(Sender: TObject);
begin
  Randomize;

  InitGameSetup();
end;...

procedure TfrmMain.InitGameSetup();
begin
  SetWindowProperties();
  InitBackGround();
  InitMainMenu();
  InitGameBoard();
  InitScrabbleTileRack();
  InitPlayers();
//  GameLoop();
end; ...

procedure TfrmMain.InitPlayers();
var
  I : Integer;
  sName, sSurname : string;
begin
  setLength(Players, NUMBER_OF_PLAYERS);
  for I := 1 to High(Players) do
    begin
      GetPlayer(); ---------------- problem is here
      with Players[I] do
        begin
          Name := sName;
          Surname := sSurname;
        end;
    end;
end;...

procedure TfrmMain.GetPlayer();
begin
  frmGetPlayer.Show;
end;

我的frmGetPlayer:

unit getPlayer_u;

interface

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

type
  TfrmGetPlayer = class(TForm)
    btnSubmit: TButton;
    edtName: TEdit;
    edtSurname: TEdit;
    procedure FormCreate(Sender: TObject);
    procedure btnSubmitClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    sPlayerName, sPlayerSurname : string;
  end;

var
  frmGetPlayer: TfrmGetPlayer;

implementation

{$R *.dfm}

procedure TfrmGetPlayer.btnSubmitClick(Sender: TObject);
begin
  sPlayerName := edtName.Text;
  sPlayerSurname := edtSurname.Text;

  if not ((Length(sPlayerName) >= 1) and (Length(sPlayerSurname) >= 1)) then
    MessageDlg('Please enter a name and surname.', mtInformation, [mbOK], 0)
  else
    Self.Free;
end;

procedure TfrmGetPlayer.FormCreate(Sender: TObject);
begin
  with Self do
    begin
      Position := poScreenCenter;
      BorderStyle := bsDialog;
    end;
end;

end.

我的dpr:

program main_p;

uses
  Forms,
  main_u in 'main_u.pas' {frmMain},
  getPlayer_u in 'getPlayer_u.pas' {frmGetPlayer};

{$R *.res}

begin
  Application.Initialize;
  Application.MainFormOnTaskbar := True;
  Application.CreateForm(TfrmMain, frmMain);
  Application.Run;
end.

错误:

Answer 1

程序启动时只会自动创建MainForm对象.在其OnCreate事件中,尚未创建您的Player Form对象,因此该frmGetPlayer变量未指向有效对象.

frmGetPlayer是一个全局变量,所以它最初是nil.错误消息告诉您正在访问地址0附近的无效内存,这几乎总是指示通过nil指针访问类的成员.

因此,frmGetPlayer.Show()在创建Player Form对象并指定frmGetPlayer为指向它之后才能调用.你展示的代码没有做到.