Update GUI while JSlider is moving - Java

This is a discussion on Update GUI while JSlider is moving - Java ; Knute Johnson a écrit : >> I want to program a feature where the user moves a JSlider which >> after some calculations shows a result in the GUI depending on the >> slider's position. It works now fully in ...

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Update GUI while JSlider is moving

  1. Default Update GUI while JSlider is moving

    Knute Johnson a écrit :
    >> I want to program a feature where the user moves a JSlider which
    >> after some calculations shows a result in the GUI depending on the
    >> slider's position. It works now fully in the EDT but lags a lot.
    >>
    >> This is because the slider creates continously events and each event
    >> must be calculated and shown.
    >>
    >> What would be the optimal architecture for such a construct. How can
    >> I drop the processing of events if the GUI lags more than a certain
    >> time behind the slider position.


    > You need to take a look at JSlider.getValueIsAdjusting(). With this
    > method you can test in your ChangeListener whether the slider is
    > moving. If it is, don't bother to update your GUI until it stops. Or
    > make occaisional updates while it is moving.


    I want to update my GUI only when the slider is moving. So your second
    solution, ie. making occasional updates seems adapted.

    How could I implement that? Maybe I can just compare the present time to
    the last repaint time and if the differenc is above a value (say 0.1s),
    call a repaint. Is this good design (especially with this hard coded
    value of 0.1 s)?

    Phil
    PS: Sorry to JT for hijacking his thread...

  2. Default Re: Update GUI while JSlider is moving

    Philipp wrote:
    >Knute Johnson a écrit :

    ...
    > > You need to take a look at JSlider.getValueIsAdjusting().

    ...
    >How could I implement that?


    <sscce>
    import javax.swing.*;
    import javax.swing.event.*;

    public class SliderValue
    extends JPanel
    implements ChangeListener {

    JSlider slider;
    JLabel message;

    SliderValue() {
    super(new java.awt.GridLayout(0,1));
    slider = new JSlider(1,100);
    slider.addChangeListener( this );

    message = new JLabel( "50" );

    add(slider);
    add(message);
    }

    /** The ChangeEvents will be continuously dumped
    to the JLabel, but we only want the pop-up
    (animation speed, ..whatever) to be updated/appear
    once the user has *released* the slider. */
    public void stateChanged(ChangeEvent ce) {
    message.setText( "" + slider.getValue() );
    if ( !slider.getValueIsAdjusting() ) {
    JOptionPane.showMessageDialog(null,
    "Value selected: " + slider.getValue() );
    }
    }

    public static void main(String[] args) {
    SliderValue sv = new SliderValue();
    JOptionPane.showMessageDialog( null, sv );
    }
    }
    </sscce>

    --
    Andrew Thompson
    http://www.athompson.info/andrew/

    Message posted via JavaKB.com
    http://www.javakb.com/Uwe/Forums.aspx/java-gui/200706/1


  3. Default Re: Update GUI while JSlider is moving

    Philipp wrote:
    ...
    >I want to update my GUI only when the slider is moving.


    Huhh? I read that as *not* moving for some (bizarre)
    reason. My bad.

    --
    Andrew Thompson
    http://www.athompson.info/andrew/

    Message posted via JavaKB.com
    http://www.javakb.com/Uwe/Forums.aspx/java-gui/200706/1


  4. Default Re: Update GUI while JSlider is moving

    Philipp <sicsicsic@freesurf.ch> wrote:
    > Knute Johnson a écrit :
    > > You need to take a look at JSlider.getValueIsAdjusting(). With this
    > > method you can test in your ChangeListener whether the slider is
    > > moving. If it is, don't bother to update your GUI until it stops. Or
    > > make occaisional updates while it is moving.

    >
    > I want to update my GUI only when the slider is moving. So your second
    > solution, ie. making occasional updates seems adapted.
    >
    > How could I implement that? Maybe I can just compare the present time to
    > the last repaint time and if the differenc is above a value (say 0.1s),
    > call a repaint. Is this good design (especially with this hard coded
    > value of 0.1 s)?


    Repaint events are coalesced in the event queue automatically by the
    event queue implementation, so I think you're doing more work than
    necessary. Just call repaint() from the ChangeListener, and repaint in
    paintComponent. This will update as often as possible, but no more
    often, so the most lag you'll get is the time required to paint once.
    The effect described upthread, where the painting falls behind and
    catches up in steps, can't occur with repaint events.

    A way to mess this up is to do significant calculation in the
    ChangeListener in addition to calling repaint() and let those get behind
    regardless of painting. If this is a problem, you could try to avoid
    the issue by setting flags that arrange for the calculation to be done
    in paintComponent instead (of course, storing the result so you don't
    repeat the calculation for EVERY repaint).

    (If the calculation is TOO expensive, then it should be moved into an
    alternate thread; but if that's needed, you have no reasonable hope of
    updating your GUI as the slider is moving anyway.)

    --
    Chris Smith

  5. Default Re: Update GUI while JSlider is moving

    Chris Smith a écrit :
    > Philipp <sicsicsic@freesurf.ch> wrote:
    >> Knute Johnson a écrit :
    >> > You need to take a look at JSlider.getValueIsAdjusting(). With this
    >> > method you can test in your ChangeListener whether the slider is
    >> > moving. If it is, don't bother to update your GUI until it stops. Or
    >> > make occaisional updates while it is moving.

    >>
    >> I want to update my GUI only when the slider is moving. So your second
    >> solution, ie. making occasional updates seems adapted.
    >>
    >> How could I implement that? Maybe I can just compare the present time to
    >> the last repaint time and if the differenc is above a value (say 0.1s),
    >> call a repaint. Is this good design (especially with this hard coded
    >> value of 0.1 s)?

    >
    > Repaint events are coalesced in the event queue automatically by the
    > event queue implementation, so I think you're doing more work than
    > necessary. Just call repaint() from the ChangeListener, and repaint in
    > paintComponent. This will update as often as possible, but no more
    > often, so the most lag you'll get is the time required to paint once.
    > The effect described upthread, where the painting falls behind and
    > catches up in steps, can't occur with repaint events.
    >
    > A way to mess this up is to do significant calculation in the
    > ChangeListener in addition to calling repaint() and let those get behind
    > regardless of painting. If this is a problem, you could try to avoid
    > the issue by setting flags that arrange for the calculation to be done
    > in paintComponent instead (of course, storing the result so you don't
    > repeat the calculation for EVERY repaint).
    >
    > (If the calculation is TOO expensive, then it should be moved into an
    > alternate thread; but if that's needed, you have no reasonable hope of
    > updating your GUI as the slider is moving anyway.)
    >


    Thanks for your very complete answer. I think I will end up implementing
    your last solution. The one with a different thread. This also because
    the repaint method cannot be easily adapted to do the computation.

    Philipp

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