Delphi XE5-需要奇怪的行為幫助

Question

我正在處理將我的應用程序日志記錄到文件的TLogger類。

我必須從文件獲取日志到TMemo：1.將TMemo分配給TLogger類，然后將True分配給DisplayInMemo屬性，然后僅調用GetLogFromFile（）； 2.調用GetLogsFromFile（）; 然后Self.Memo1.Text：= TLogger.LogsResult;

下面...評論解決方案工作正常...未評論解決方案僅每2單擊一次按鈕4即可工作

procedure TForm1.Button4Click(Sender: TObject);   // get log.file to memo
begin
  // automatic forwarding logs from File to TMemo - it works!
  //logger.DisplayMemo := Self.Memo1;
  //logger.DisplayInMemo := True;
  //logger.GetLogsFromFile();

  // tested - half-automatic method of formwarding logs to TMemo - works every 2 clicks :(
  logger.DisplayInMemo := False;
  logger.GetLogsFromFile();
  Self.Memo1.Text := logger.LogsResult;
end;

整個TLogger實現：

unit Logger;

interface

uses
  System.IOUtils, System.TypInfo, System.SysUtils, FMX.Forms, FMX.Dialogs, System.Classes, FMX.Graphics, FMX.ExtCtrls, LoggerThread, FMX.Memo;

type

  TLogger = class
  private
    FileName : String;                // name of file to log
    FilePath : String;                // path to app / log-file

    LStringResult : String;           // result of thread log.file reading
    LLoggerMemo : TMemo;              // copy of memo - place where GetLogsFromFile put results

    LDisplayInMemo : Boolean;         // bool - if True  GetLogsFromFile puts results to DisplayMemo, otherwise waiting in LogsResult
    NewLoggerThread : TLoggerThread;  // thread object - created in Create()

    procedure GetLogsFromFileThreadTerminateHandler(sender: TObject);

  public
    constructor Create(); overload;                     // open or create 'development.log'
    constructor Create(LogFileName : String); overload; // open or create LogFileName for logging
    destructor Destroy(); overload;                     // cleaner of TLogger object
    // main procedures
    procedure Log(LogString : String);                  // add line to log file
    procedure GetLogsFromFile();                        // get all logs from log file to string
    // settings, reading results,
    property DisplayInMemo : Boolean read LDisplayInMemo write LDisplayInMemo; //bool - if True  GetLogsFromFile puts results to DisplayMemo, otherwise waiting in LogsResult
    property LogsResult : String read LStringResult write LStringResult;       //string results after Getters from TLogger usage
    property DisplayMemo : TMemo read LLoggerMemo write LLoggerMemo;           // sets TMemo where results will be put if DisplayInMemo set to True
  end;

implementation

  constructor TLogger.Create();
  begin
    {$IFDEF Android}
      FilePath := TPath.GetDownloadsPath + System.SysUtils.PathDelim;
    {$ELSE}
      FilePath := ExtractFilePath(ParamStr(0));
    {$ENDIF}
    FileName := 'development.log';
    LDisplayInMemo := False;
    // inherited
    inherited Create;
  end;

  constructor TLogger.Create(LogFileName : String);
  begin
    {$IFDEF Android}
      FilePath := TPath.GetDownloadsPath + System.SysUtils.PathDelim;
      //TPath.Combine(TPath.GetDocumentsPath,'test.txt');  // to have / \ auto-change
    {$ELSE}
      FilePath := ExtractFilePath(ParamStr(0));
    {$ENDIF}
    FileName := LogFileName;
    LDisplayInMemo := False;
    // inherited
    inherited Create;
  end;

  destructor TLogger.Destroy();
  begin
    inherited Destroy;
  end;

  // adds a sigle line to log file with date time
  procedure TLogger.Log(LogString : String);
  begin
    NewLoggerThread :=  TLoggerThread.Create(True);
    NewLoggerThread.FreeOnTerminate := True;
    NewLoggerThread.Log := LogString;                                    //log to write - date time then added in execute
    NewLoggerThread.LoggerInstruction := TLoggerInstruction.liLogToFile; //set instuction for thread - LogToFile
    NewLoggerThread.FileName := FileName;  //file to write
    NewLoggerThread.FilePath := FilePath;  //path to file

    try
      NewLoggerThread.Start;
    except
      NewLoggerThread.Free();
    end;

  end;

  // results String with LogFile content
  procedure TLogger.GetLogsFromFile();
  begin
    NewLoggerThread :=  TLoggerThread.Create(True);
    NewLoggerThread.FreeOnTerminate := True;
    NewLoggerThread.OnTerminate := GetLogsFromFileThreadTerminateHandler;
    NewLoggerThread.FileName := FileName;  //file to write
    NewLoggerThread.FilePath := FilePath;  //path to file
    NewLoggerThread.LoggerInstruction := TLoggerInstruction.liGetLogsFromFile; //set instuction for thread - GetLogFromFile

    try
      NewLoggerThread.Start;
    except
      NewLoggerThread.Free();
    end;

  end;

  procedure TLogger.GetLogsFromFileThreadTerminateHandler(sender: TObject);
  begin
    LStringResult := (Sender as TLoggerThread).StringResult;
    if LDisplayInMemo then
        LLoggerMemo.Text := (Sender as TLoggerThread).StringResult;
  end;

end.

如您所見，唯一的區別在於LDisplayInMemo：如果為True，則TMemo填充日志...當為False時，我需要2次單擊按鈕4才能在TMemo中獲得結果...

  procedure TLogger.GetLogsFromFileThreadTerminateHandler(sender: TObject);
  begin
    LStringResult := (Sender as TLoggerThread).StringResult;
    if LDisplayInMemo then
        LLoggerMemo.Text := (Sender as TLoggerThread).StringResult;
  end;

有任何想法嗎？ 老實說，我不知道這兩種解決方案出現差異的原因是什么：（我還在Self.Memo1.Text：= logger.LogsResult;之后嘗試了ProcessMessages。

Answer 1

以下代碼僅在您第二次單擊該按鈕時才起作用的原因是，您實際上要獲取日志信息的代碼在另一個線程中運行...它是異步的 ！

logger.DisplayInMemo := False;
logger.GetLogsFromFile();
Self.Memo1.Text := logger.LogsResult; //This line runs AT THE SAME TIME you're getting logs!

注意 ：您正在讀取logger.LogsResult的值， logger.LogsResult 才從LoggerThread獲取值。

再次單擊該按鈕時，線程已完成運行（第一次），現在您可以讀取一個值。

您的評論部分起作用的原因是，您僅在線程終止時（即完成工作時）分配備忘錄文本。