QProgressDialog Class Reference

Provides feedback on the progress of a slow operation. More...

#include <qprogressdialog.h>

Inherits QSemiModal.

List of all member functions.

Public Members

• QProgressDialog ( QWidget * parent=0, const char * name=0, bool modal=FALSE, WFlags f=0 ) 
• QProgressDialog ( const QString & labelText, const QString & cancelButtonText, int totalSteps, QWidget * parent=0, const char * name=0, bool modal=FALSE, WFlags f=0 ) 
• ~QProgressDialog () 
• void setLabel ( QLabel * ) 
• void setCancelButton ( QPushButton * ) 
• void setBar ( QProgressBar * ) 
• bool wasCancelled () const
• int totalSteps () const
• int progress () const
• virtual QSize sizeHint () const
• QString labelText () const
• void setAutoReset ( bool b ) 
• bool autoReset () const
• void setAutoClose ( bool b ) 
• bool autoClose () const
• int minimumDuration () const

Public Slots

• void cancel () 
• void reset () 
• void setTotalSteps ( int totalSteps ) 
• void setProgress ( int progress ) 
• void setLabelText ( const QString & ) 
• void setCancelButtonText ( const QString & ) 
• void setMinimumDuration ( int ms ) 

Signals

• void cancelled () 

Protected Slots

• void forceShow () 

Properties

Detailed Description

A progress dialog is used to give the user an indication of how long an operation is going to take to perform, and to reassure them that the application has not frozen. It also gives the user an opportunity to abort the operation.

A potential problem with progress dialogs is that it is difficult to know when to use them, as operations take different amounts of time on different computer hardware. QProgressDialog offers a solution to this problem: it estimates the time the operation will take (based on time for steps), and only shows itself if that estimate is beyond minimumDuration() (4 seconds by default).

Use setTotalSteps() (or the constructor) to set the number of "steps" in the operation and call setProgress() as the operation progresses. The step value can be chosen arbitrarily. It can be eg. the number of files copied, the number of bytes received, or the number of iterations through the main loop of your algorithm. You must call setProgress() with parameter 0 initially, and with parameter totalSteps() at the end.

The dialog will automatically be reset and hidden at the end of the operation, Use setAutoReset() and setAutoClose() to change this behavior.

There are two ways of using QProgressDialog, modal and non-modal.

Using a modal QProgressDialog is simpler for the programmer, but you have to call qApp->processEvents() to keep the event loop running and prevent the application from freezing. Do the operation in a loop, calling setProgress() at intervals, and checking for cancellation with wasCancelled().

Example:

    QProgressDialog progress( "Copying files...", "Abort Copy", numFiles,
                                this, "progress", TRUE );
    for (int i=0; i<numFiles; i++) {
        progress.setProgress( i );
        qApp->processEvents();

        if ( progress.wasCancelled() )
            break;
        ... // copy one file
    }
    progress.setProgress( numFiles );

A non-modal progress dialog is suitable for operations that take place in the background, where the user is able to interact with the application. Such operations are typically based on QTimer (or QObject::timerEvent()), QSocketNotifier, or QUrlOperator; or performed in a separate thread. A QProgressBar in the status bar of your main window is often an alternative to a non-modal progress dialog.

You need an event loop to be running. Connect the cancelled() signal to a slot that stops the operation, and call setProgress() at intervals.

Example:

  Operation::Operation( QObject *parent = 0 )
      : QObject( parent ), steps(0)
  {
      pd = new QProgressDialog( "Operation in progress.", "Cancel", 100 );
      connect( pd, SIGNAL(cancelled()), this, SLOT(cancel()) );
      t = new QTimer( this );
      connect( t, SIGNAL(timeout()), this, SLOT(perform()) );
      t->start(0);
  }

  void Operation::perform()
  {
      pd->setProgress( steps );
      ...       //perform one percent of the operation
      steps++;
      if ( steps > pd->totalSteps() )
                t->stop();
  }

  void Operation::cancel()
  {
      t->stop();
      ...       //cleanup
  }

In both modes, the progress dialog may be customized by replacing the child widgets with custom widgets, using setLabel(), setBar() and setCancelButton(). The functions setLabelText() and setCancelButtonText() sets the texts shown.

See also QDialog, QProgressBar and GUI Design Handbook: Progress Indicator

Examples: progress/progress.cpp

Member Function Documentation

QProgressDialog::QProgressDialog ( QWidget * creator=0, const char * name=0, bool modal=FALSE, WFlags f=0 )

Constructs a progress dialog.

Default settings:

• The label text is empty.
• The cancel button text is "Cancel".
• The total number of steps is 100.

parent, name, modal, and f are sent to the QSemiModal::QSemiModal() constructor. Note that if modal is FALSE (the default), you will need to have an event loop proceeding for any redrawing of the dialog to occur. If it is TRUE, the dialog ensures events are processed when needed.

See also setLabelText(), setLabel(), setCancelButtonText(), setCancelButton() and setTotalSteps().

QProgressDialog::QProgressDialog ( const QString & labelText, const QString & cancelButtonText, int totalSteps, QWidget * creator=0, const char * name=0, bool modal=FALSE, WFlags f=0 )

Constructs a progress dialog.

labelText is text telling the user what is progressing.

cancelButtonText is the text on the cancel button, or 0 if no cancel button is to be shown.

totalSteps is the total number of steps in the operation of which this progress dialog shows the progress. For example, if the operation is to examine 50 files, this value would be 50, then before examining the first file, call setProgress(0), and after examining the last file call setProgress(50).

name, modal, and f are sent to the QSemiModal::QSemiModal() constructor. Note that if modal is FALSE (the default), you will need to have an event loop proceeding for any redrawing of the dialog to occur. If it is TRUE, the dialog ensures events are processed when needed.

See also setLabelText(), setLabel(), setCancelButtonText(), setCancelButton() and setTotalSteps().

QProgressDialog::~QProgressDialog ()

Destructs the progress dialog.

bool QProgressDialog::autoClose () const

Returns if the dialog gets hidden by reset().

See also setAutoClose().

bool QProgressDialog::autoReset () const

Returns if the dialog resets itself when progress() equals totalSteps().

See also setAutoReset().

void QProgressDialog::cancel () [slot]

Reset the progress dialog. wasCancelled() becomes TRUE until the progress dialog is reset. The progress dialog becomes hidden.

void QProgressDialog::cancelled () [signal]

This signal is emitted when the cancel button is clicked. It is connected to the cancel() slot by default.

See also wasCancelled().

void QProgressDialog::closeEvent ( QCloseEvent * e ) [virtual protected]

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

void QProgressDialog::forceShow () [protected slot]

Shows the dialog if it is still hidden after the algorithm has been started and the minimumDuration is over.

See also setMinimumDuration().

QString QProgressDialog::labelText () const

Returns the labels text.

See also setLabelText.

int QProgressDialog::minimumDuration () const

Returns the currently set minimum duration for the QProgressDialog

See also setMinimumDuration().

int QProgressDialog::progress () const

Returns the current amount of progress, or -1 if the progress counting has not started.

See also setProgress().

void QProgressDialog::reset () [slot]

Reset the progress dialog. The progress dialog becomes hidden if autoClose() is TRUE.

See also setAutoClose() and setAutoReset().

void QProgressDialog::resizeEvent ( QResizeEvent * ) [virtual protected]

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

void QProgressDialog::setAutoClose ( bool b )

If you set b to TRUE, the dialog gets closed (hidden) if reset() is called, else this does not happen.

See also autoClose() and setAutoReset().

void QProgressDialog::setAutoReset ( bool b )

If you set b to TRUE, the progress dialog calls reset() if progress() equals totalSteps(), if you set it to FALSE, this does not happen.

See also autoReset() and setAutoClose().

void QProgressDialog::setBar ( QProgressBar * bar )

Sets the progress bar widget. The progress dialog resizes to fit. The progress bar becomes owned by the progress dialog and will be deleted when necessary.

void QProgressDialog::setCancelButton ( QPushButton * cancelButton )

Sets the cancellation button. The button becomes owned by the progress dialog and will be deleted when necessary, so do not pass the address of an object on the stack.

See also setCancelButtonText().

void QProgressDialog::setCancelButtonText ( const QString & cancelButtonText ) [slot]

Sets the cancellation button text.

See also setCancelButton().

void QProgressDialog::setLabel ( QLabel * label )

Sets the label. The progress dialog resizes to fit. The label becomes owned by the progress dialog and will be deleted when necessary, so do not pass the address of an object on the stack.

See also setLabelText().

Examples: progress/progress.cpp

void QProgressDialog::setLabelText ( const QString & text ) [slot]

Sets the label text. The progress dialog resizes to fit.

See also setLabel().

void QProgressDialog::setMinimumDuration ( int ms ) [slot]

Sets the minimum duration to ms milliseconds. The dialog will not appear if the anticipated duration of the progressing task is less than the minimum duration.

If ms is 0 the dialog is always shown as soon as any progress is set.

See also minimumDuration().

Examples: progress/progress.cpp

void QProgressDialog::setProgress ( int progress ) [slot]

Sets the current amount of progress made to prog units of the total number of steps. For the progress dialog to work correctly, you must at least call this with the parameter 0 initially, then later with QProgressDialog::totalSteps(), and you may call it any number of times in between.

Warning: If the progress dialog is modal (see QProgressDialog::QProgressDialog()), this function calls QApplication::processEvents(), so take care that this does not cause undesirable re-entrancy to your code. For example, don't use a QProgressDialog inside a paintEvent()!

See also progress().

Examples: progress/progress.cpp

void QProgressDialog::setTotalSteps ( int totalSteps ) [slot]

Sets the total number of steps.

See also totalSteps() and QProgressBar::setTotalSteps().

void QProgressDialog::showEvent ( QShowEvent * e ) [virtual protected]

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

QSize QProgressDialog::sizeHint () const [virtual]

Returns a size which fits the contents of the progress dialog. The progress dialog resizes itself as required, so this should not be needed in user code.

Reimplemented from QWidget.

void QProgressDialog::styleChange ( QStyle & s ) [virtual protected]

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

int QProgressDialog::totalSteps () const

Returns the total number of steps.

See also setTotalSteps() and QProgressBar::totalSteps().

Examples: progress/progress.cpp

bool QProgressDialog::wasCancelled () const

Returns the TRUE if the dialog was cancelled, otherwise FALSE.

See also setProgress(), cancel() and cancelled().

Examples: progress/progress.cpp

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