如何使用动画使一个JavaFX滑块旋钮只移动到刻度线？

Question

继续本问题中的讨论，如何使JavaFX滑块以离散的步骤移动？我添加了一个“播放”按钮和一个时间线，这样当用户单击“播放”按钮时，滑块的旋钮就会重复地前进到下一个刻度线，直到滑块的末端或用户单击“停止”按钮。不幸的是，动画运行的时间越长，旋钮在刻度线之间的移动就越多（是的，setSnaptoticks是真的）。而且，滑块的值也不是我所期望的。理想情况下，它应该是“-60、-59、-58等”，但时间线每次以很小的分数移动滑块旋钮（例如-55.188833333333335）。这个问题我已经研究了很长时间了。下面是我的代码：

public class SliderTest extends Application {
StringConverter<Double> stringConverter = new StringConverter<>() {

    @Override
    public String toString( Double object ) {
        long seconds = object.longValue();
        long minutes = TimeUnit.SECONDS.toMinutes( seconds );
        long remainingseconds = Math.abs( seconds - TimeUnit.MINUTES.toSeconds( minutes ) );
        return String.format( "%02d", minutes ) + ":" + String.format( "%02d", remainingseconds );
    }

    @Override
    public Double fromString( String string ) {
        return null;
    }
};

@Override
public void start( Stage primaryStage ) throws Exception {
    try {
        Pane pane = new Pane();
        pane.setStyle( "-fx-background-color: black;" );

        Slider slider = new Slider( -60, 0, -60 );
        slider.setBlockIncrement( 60 );
        slider.setMajorTickUnit( 60 );
        slider.setMinorTickCount( 60 );
        slider.setShowTickLabels( true );
        slider.setShowTickMarks( true );
        slider.setSnapToTicks( true );
        slider.setLabelFormatter( stringConverter );
        slider.setPrefWidth( 1303 );

        Button playStopButton = new Button( "Play" );
        HBox buttonHBox = new HBox( playStopButton );
        buttonHBox.setAlignment( Pos.CENTER );
        Text sliderTime = new Text( "Time" );
        sliderTime.setFont( new Font( 12 ) );
        sliderTime.setFill( Color.WHITE );
        sliderTime.setText( stringConverter.toString( slider.getValue() ) );

        HBox hbox = new HBox( slider, sliderTime, buttonHBox );
        hbox.setPrefWidth( 1428 );
        hbox.setSpacing( 10 );
        hbox.setAlignment( Pos.TOP_CENTER );

        pane.getChildren().add( hbox );

        Scene scene = new Scene( pane );
        scene.getStylesheets().add( getClass().getResource( "/css/slider.css" ).toExternalForm() );
        primaryStage.setScene( scene );
        primaryStage.show();

        Timeline timeline = new Timeline(
                new KeyFrame( Duration.ZERO, new KeyValue( slider.valueProperty(), slider.getValue() ) ),
                new KeyFrame( Duration.seconds( -slider.getValue() ), new KeyValue( slider.valueProperty(), 0 ) ) );

        slider.valueProperty().addListener( ( observable, oldValue, newValue ) -> {
            slider.setValue( newValue.intValue() );
            
            System.out.println( slider.getValue() + " | " + newValue.doubleValue() );

            // Set the text to the slider's new value.
            sliderTime.setText( stringConverter.toString( slider.getValue() ) );

            if ( newValue.doubleValue() == 0 ) {
                // Reset the timeline and the text for the sliderButton.
                timeline.stop();
                timeline.getKeyFrames().clear();
                playStopButton.setText( "Stop" );
            }
        } );

        slider.setOnMousePressed( event -> {
            // On mouse down, reset the timeline.
            timeline.stop();
            timeline.getKeyFrames().clear();
        } );

        slider.setOnMouseReleased( event -> {
            // Set the new start position of the timeline.
            timeline.getKeyFrames().add(
                    new KeyFrame( Duration.ZERO, new KeyValue( slider.valueProperty(), slider.getValue() ) ) );
            timeline.getKeyFrames().add( new KeyFrame( Duration.seconds( -slider.getValue() ),
                    new KeyValue( slider.valueProperty(), 0 ) ) );

            // Play the animation only if it was playing before.
            if ( playStopButton.getText().equals( "Pause" ) ) {
                timeline.play();
            }
            // Change the image for the playStopButton to stop when the thumb is moved to zero.
            else if ( playStopButton.getText().equals( "Stop" ) && ( slider.getValue() < 0 ) ) {
                playStopButton.setText( "Play" );
            }
        } );

        playStopButton.setOnMouseClicked( event -> {
            // Ignore mouse clicks on the playStopButton when the slider is at time zero.
            if ( slider.getValue() != 0 ) {
                if ( ( timeline.getStatus() == Status.STOPPED ) || ( timeline.getStatus() == Status.PAUSED ) ) {
                    playStopButton.setText( "Pause" );
                    timeline.play();
                }
                else if ( timeline.getStatus() == Status.RUNNING ) {
                    playStopButton.setText( "Play" );
                    timeline.pause();
                }
            }
        } );
    } catch ( Exception e ) {
        e.printStackTrace();
    }
}

public static void main( String[] args ) {
    launch( args );
}

Answer 1

部分问题是在滑块的设置中出现的。问题的另一部分是我对时间线的定义。基本上，我让Java来定义滑块按钮的所有值，不管刻度线在哪里，这不是我想要的（尽管它确实有助于平滑的动画）。但是在做了以下更改后，滑块的按钮每秒钟都会前进到下一个刻度线，这就是我想要的。与以前相比，滑块的按钮总是在两个刻度线之间。

        slider.setMajorTickUnit( 1 );

        Timeline timeline = new Timeline(
                new KeyFrame( Duration.seconds( 1 ), event -> {
                    slider.setValue( slider.getValue() + 1 );
                } ) );
        timeline.setCycleCount( Math.abs( Double.valueOf( slider.getValue() ).intValue() ) );