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  1. 25th January 2007, 01:29 #11
    spurious_interrupt
    spurious_interrupt is offline Beginner
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    Jan 2007
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    Default Re: Communication between QThread and Yes/No QMessageBox?

    I have an application that uses tape drives. The thread needs to ask if there are any more tapes for the job, SCSI errors, file dialogs...

    This method uses QT3, I have not ported this application to QT4 yet.

    Qt Code: 
    1. in your application
    2.  
    3. void  TapeMan::customEvent( QCustomEvent *event )
    4. {
    5.  if( event->type() == QEvent::User + 3 ) // display message box
    6.     {
    7.     MessageBoxEvent  *me = ( MessageBoxEvent* )event;
    8.     ThreadMessageBox  *tm = me->tm;
    9.  
    10.     if( me->kind == TMSG_WARN )
    11.         tm->messageResult = QMessageBox::warning( this, me->caption, me->message, 
    12.                 me->button0, me->button1, me->button2 );
    13.     if( me->kind == TMSG_INFO )
    14.         tm->messageResult = QMessageBox::information( this, me->caption, 
    15.                 me->message, me->button0, me->button1, me->button2 );
    16.     if( me->kind == TMSG_STOP )
    17.         tm->messageResult = QMessageBox::critical( this, me->caption, me->message, 
    18.                 me->button0, me->button1, me->button2 );
    19.     }
    20. }
    21.  
    22. and then 2 classes
    23.  
    24. #ifndef THREADMESSAGEBOX_H
    25. #define THREADMESSAGEBOX_H
    26.  
    27. #include  <qstring.h>
    28. #include  <qmessagebox.h>
    29.  
    30. class ThreadMessageBox
    31. {
    32. public: 
    33. 	ThreadMessageBox( THREAD_MESSAGE kind, const QString &caption, const 
    34.                 QString& message, int button0, int button1=QMessageBox::NoButton, 
    35.                 int button2=QMessageBox::NoButton );
    36.  
    37. 	~ThreadMessageBox();
    38.  
    39. 	int  messageResult;
    40. };
    41.  
    42. #endif
    43.  
    44. #include  "threadmessagebox.h"
    45. #include  "messageboxevent.h"
    46.  
    47. #include  <qapplication.h>
    48.  
    49. extern TapeMan  *gApp;
    50.  
    51. ThreadMessageBox::ThreadMessageBox( THREAD_MESSAGE kind, const QString &caption,
    52.                 const QString& message, int button0, int button1, int button2 )
    53. {
    54.     MessageBoxEvent  *mess = new  MessageBoxEvent( this, kind, caption, message, 
    55.                 button0, button1, button2 );
    56.  
    57.     messageResult = -99999;
    58.  
    59.     QApplication::postEvent( gApp, mess );	// post event
    60.  
    61.     while( messageResult == -99999 )         // wait
    62.         {
    63.         sleep( 1 );
    64.         }
    65. }
    66.  
    67. ThreadMessageBox::~ThreadMessageBox()
    68. {
    69. }
    70.  
    71. #ifndef MESSAGE_BOX_EVENT_H
    72. #define MESSAGE_BOX_EVENT_H
    73.  
    74. #include  <qevent.h>
    75. #include  <qmessagebox.h>
    76. #include  <qdeepcopy.h>
    77.  
    78. class  ThreadMessageBox;
    79.  
    80. class MessageBoxEvent : public QCustomEvent
    81. {
    82. public: 
    83.     MessageBoxEvent( ThreadMessageBox *tm, THREAD_MESSAGE kind, const QString &caption,
    84.                 const QString& message, int button0, int button1=QMessageBox::NoButton, 
    85.                 int button2=QMessageBox::NoButton );
    86.     ~MessageBoxEvent();
    87.  
    88.    THREAD_MESSAGE  kind;	// kind of message box
    89.  
    90.     QDeepCopy<QString>  caption;	// caption for message box
    91.     QDeepCopy<QString>  message;	// text for message
    92.  
    93.     int  button0;			// buttons to display
    94.     int  button1;
    95.     int  button2;
    96.  
    97.     ThreadMessageBox  *tm;		// pointer to thread message box
    98. };
    99. #endif
    100.  
    101. #include "messageboxevent.h"
    102.  
    103. MessageBoxEvent::MessageBoxEvent( ThreadMessageBox *tm, THREAD_MESSAGE kind, 
    104.                 const QString &caption, const QString& message,
    105.                 int button0, int button1, int button2 ) : QCustomEvent( QEvent::User+3 )
    106. {
    107.     this->kind    = kind;
    108.     this->caption = caption;
    109.     this->message = message;
    110.     this->button0 = button0;
    111.     this->button1 = button1;
    112.     this->button2 = button2;
    113.     this->tm = tm;
    114. }
    115.  
    116. MessageBoxEvent::~MessageBoxEvent()
    117. {
    118. }
    119.  
    120. to get a message box from your thread
    121.  
    122.     ThreadMessageBox  mess = ThreadMessageBox( TMSG_INFO, "Tape Done", "Are there any more tapes",
    123.                 QMessageBox::Yes, QMessageBox::No );  // will block until message box is closed
    124.  
    125.     if( mess.messageResult == QMessageBox::Yes )
    126.         // do action here!
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    You need to use QDeepCopy's to insure each thread has a unique copy of the strings. This is not needed in QT4. The wait loop is a simple sleep. That is all that was needed for this application.
    Last edited by jacek; 25th January 2007 at 01:54. Reason: wrapped too long lines
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