单击轨道时使 JSlider 缩略图出现

Question

我正在尝试修改 JSlider，以便在单击轨道时出现缩略图（旋钮）。我正在调整找到的代码 here 来实现这个目标。本质上，我通过最初将其大小设置为 0,0 来隐藏拇指。当鼠标单击轨道时，拇指会更改其大小以使其出现。我遇到的问题是轨道也没有出现。但是，一旦单击曲目，它就会出现。是否可以在不改变轨道的情况下修改拇指（或以某种方式隐藏它）？任何建议，将不胜感激。

public class SliderUI extends MetalSliderUI {
private boolean displayThumb = false;
private int x = 0;
private int y = 0;

public SliderUI(){
    super();
}


@Override
 protected Dimension getThumbSize() {
     return new Dimension(x, y);
 }

@Override
protected void scrollDueToClickInTrack(int direction) {

    //keep displaying thumb once true
    if(!displayThumb){
        x = 15;
        y = 20;
        displayThumb = true;
    }
    int value = slider.getValue(); 
    if (slider.getOrientation() == JSlider.HORIZONTAL) {
        value = this.valueForXPosition(slider.getMousePosition().x);
    } else if (slider.getOrientation() == JSlider.VERTICAL) {
        value = this.valueForYPosition(slider.getMousePosition().y);
    }
    slider.setValue(value);
}

}

更新：我也用 paintThumb() 尝试过类似的方法，但无济于事。我收到一个空指针异常错误。这是我尝试过的：

public class SliderUI extends MetalSliderUI {
private boolean displayThumb = false;
protected static Icon horizThumbIcon;
protected static Icon vertThumbIcon;
private static Icon SAFE_HORIZ_THUMB_ICON;
private static Icon SAFE_VERT_THUMB_ICON;

public SliderUI(){
    super();
}

private static Icon getHorizThumbIcon() {
    if (System.getSecurityManager() != null) {
        return SAFE_HORIZ_THUMB_ICON;
    } else {
        return horizThumbIcon;
    }
}

private static Icon getVertThumbIcon() {
    if (System.getSecurityManager() != null) {
        return SAFE_VERT_THUMB_ICON;
    } else {
        return vertThumbIcon;
    }
}


@Override
public void paintThumb(Graphics g)  {
       //keep displaying thumb once true
        if(!displayThumb){
            displayThumb = true;
            return;
        }
    Rectangle knobBounds = thumbRect;

    g.translate( knobBounds.x, knobBounds.y );

    if ( slider.getOrientation() == JSlider.HORIZONTAL ) {
        getHorizThumbIcon().paintIcon( slider, g, 0, 0 );
    }
    else {
        getVertThumbIcon().paintIcon( slider, g, 0, 0 );
    }

    g.translate( -knobBounds.x, -knobBounds.y );
}

@Override
protected void scrollDueToClickInTrack(int direction) {


    int value = slider.getValue(); 
    if (slider.getOrientation() == JSlider.HORIZONTAL) {
        value = this.valueForXPosition(slider.getMousePosition().x);
    } else if (slider.getOrientation() == JSlider.VERTICAL) {
        value = this.valueForYPosition(slider.getMousePosition().y);
    }
    slider.setValue(value);
}

}

Answer 1

为了将来参考，下面是我的问题的简单解决方案：

public class SliderUI extends MetalSliderUI {

    private boolean displayThumb = false;

    public SliderUI(){
        super();
    }


  @Override
    public void paintThumb(Graphics g) {
      if(displayThumb){
          super.paintThumb(g);
      }
    }

    @Override
    protected void scrollDueToClickInTrack(int direction) {
        //keep displaying thumb once true
        if(!displayThumb){
            displayThumb = true;
        }
        int value = slider.getValue(); 
        if (slider.getOrientation() == JSlider.HORIZONTAL) {
            value = this.valueForXPosition(slider.getMousePosition().x);
        } else if (slider.getOrientation() == JSlider.VERTICAL) {
            value = this.valueForYPosition(slider.getMousePosition().y);
        }
        slider.setValue(value);
    }
}

单击轨道时使 JSlider 缩略图出现

Make JSlider thumb appear upon clicking track

java

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