Java JSlider精度问题

Question

我有N个JSliders列表（N不会在程序上更改，只是随着我添加更多功能而已。当前N等于4）。所有滑块的值之和必须等于100。随着一个滑块的移动，其余的滑块应进行调整。每个滑块的值范围从0到100。

当前，当更改滑块（伪代码）时，我正在使用以下逻辑：

newValue = currentSlider.getValue

otherSliders = allSliders sans currentSlider
othersValue = summation of otherSliders values
properOthersValue = 100 - newValue

ratio = properOthersValue / othersValue

for slider in  otherSlider 
    slider.value = slider.getValue * ratio

此设置的问题是滑块的值存储为整数。因此，当我调整滑块时，会遇到精度问题：滑块会根据比例值抽动或完全不移动。同样，总价值不一定总等于100。

没有人可以解决此问题，而无需创建支持浮点数或双精度数的全新JSlider类吗？

如果您想要我想要的行为的示例，请访问：Humble Indie
Bundle
并滚动到页面底部。

谢谢

ps将值乘以比率可以使用户将值“锁定”为0。但是，当4个滑块中的3个滑块为0且第4个滑块为100时，我不确定该怎么做下。使用上面的逻辑，3个滑块的值为0，它们将保持放置状态，而第4个滑块将移动到用户放置它的位置，这使总数小于100，这是不正确的行为。

编辑

这是SSCCE：

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.*;
import java.util.LinkedList;

public class SliderDemo
{
    static LinkedList<JSlider> sliders = new LinkedList<JSlider>();

    static class SliderListener implements ChangeListener
    {
        boolean updating = false;

        public void stateChanged(ChangeEvent e)
        {
            if (updating) return;
            updating = true;

            JSlider source = (JSlider)e.getSource();

            int newValue = source.getValue();
            LinkedList<JSlider> otherSliders = new LinkedList<JSlider>(sliders);
            otherSliders.remove(source);

            int otherValue = 0;
            for (JSlider slider : otherSliders)
            {
                otherValue += slider.getValue();
            }

            int properValue = 100 - newValue;
            double ratio = properValue / (double)otherValue;

            for (JSlider slider : otherSliders)
            {
                int currentValue = slider.getValue();
                int updatedValue = (int) (currentValue * ratio);
                slider.setValue(updatedValue);
            }

            int total = 0;
            for (JSlider slider : sliders)
            {
                total += slider.getValue();
            }
            System.out.println("Total = " + total);

            updating = false;
        }
    }

    public static void main(String[] args)
    {
        JFrame frame = new JFrame("SliderDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container container = frame.getContentPane();
        JPanel sliderPanel = new JPanel(new GridBagLayout());
        container.add(sliderPanel);

        SliderListener listener = new SliderListener();

        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = 0;
        int sliderCount = 4;
        int initial = 100 / sliderCount;
        for (int i = 0; i < sliderCount; i++)
        {
            gbc.gridy = i;
            JSlider slider = new JSlider(0, 100, initial);
            slider.addChangeListener(listener);
            slider.setMajorTickSpacing(50);
            slider.setPaintTicks(true);
            sliders.add(slider);
            sliderPanel.add(slider, gbc);
        }

        frame.pack();
        frame.setVisible(true);
    }
}

Answer 1

为什么不说JSlider模型的粒度从0到1000000，并且总和为1000000，以使粒度更细？使用适用Dictionary于LabelTable
的适当名称，用户可能不会知道它的范围不是从0到100。

例如：

import java.awt.Dimension;
import java.awt.GridLayout;
import java.util.ArrayList;
import java.util.Dictionary;
import java.util.Hashtable;
import java.util.List;

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

@SuppressWarnings("serial")
public class LinkedSliders2 extends JPanel {
   private static final int SLIDER_COUNT = 5;
   public static final int SLIDER_MAX_VALUE = 1000;
   private static final int MAJOR_TICK_DIVISIONS = 5;
   private static final int MINOR_TICK_DIVISIONS = 20;
   private static final int LS_WIDTH = 700;
   private static final int LS_HEIGHT = 500;
   private JSlider[] sliders = new JSlider[SLIDER_COUNT];
   private SliderGroup2 sliderGroup = new SliderGroup2(SLIDER_MAX_VALUE);

   public LinkedSliders2() {
      Dictionary<Integer, JComponent> myDictionary = new Hashtable<Integer, JComponent>();
      for (int i = 0; i <= MAJOR_TICK_DIVISIONS; i++) {
         Integer key = i * SLIDER_MAX_VALUE / MAJOR_TICK_DIVISIONS;
         JLabel value = new JLabel(String.valueOf(i * 100 / MAJOR_TICK_DIVISIONS));
         myDictionary.put(key, value);
      }
      setLayout(new GridLayout(0, 1));
      for (int i = 0; i < sliders.length; i++) {
         sliders[i] = new JSlider(0, SLIDER_MAX_VALUE, SLIDER_MAX_VALUE
               / SLIDER_COUNT);
         sliders[i].setLabelTable(myDictionary );
         sliders[i].setMajorTickSpacing(SLIDER_MAX_VALUE / MAJOR_TICK_DIVISIONS);
         sliders[i].setMinorTickSpacing(SLIDER_MAX_VALUE / MINOR_TICK_DIVISIONS);
         sliders[i].setPaintLabels(true);
         sliders[i].setPaintTicks(true);
         sliders[i].setPaintTrack(true);
         sliderGroup.addSlider(sliders[i]);
         add(sliders[i]);
      }
   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(LS_WIDTH, LS_HEIGHT);
   }

   private static void createAndShowGui() {
      LinkedSliders2 mainPanel = new LinkedSliders2();

      JFrame frame = new JFrame("LinkedSliders");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

class SliderGroup2 {
   private List<BoundedRangeModel> sliderModelList = new ArrayList<BoundedRangeModel>();
   private ChangeListener changeListener = new SliderModelListener();
   private int maxValueSum;

   public SliderGroup2(int maxValueSum) {
      this.maxValueSum = maxValueSum;
   }

   public void addSlider(JSlider slider) {
      BoundedRangeModel model = slider.getModel();
      sliderModelList.add(model);
      model.addChangeListener(changeListener);
   }

   private class SliderModelListener implements ChangeListener {
      private boolean internalChange = false;

      @Override
      public void stateChanged(ChangeEvent cEvt) {
         if (!internalChange) {
            internalChange = true;
            BoundedRangeModel sourceModel = (BoundedRangeModel) cEvt.getSource();
            int sourceValue = sourceModel.getValue();

            int oldSumOfOtherSliders = 0;
            for (BoundedRangeModel model : sliderModelList) {
               if (model != sourceModel) {
                  oldSumOfOtherSliders += model.getValue();
               }
            }
            if (oldSumOfOtherSliders == 0) {
               for (BoundedRangeModel model : sliderModelList) {
                  if (model != sourceModel) {
                     model.setValue(1);
                  }
               }
               internalChange = false;
               return;
            }

            int newSumOfOtherSliders = maxValueSum - sourceValue;

            for (BoundedRangeModel model : sliderModelList) {
               if (model != sourceModel) {
                  long newValue = ((long) newSumOfOtherSliders * model
                        .getValue()) / oldSumOfOtherSliders;
                  model.setValue((int) newValue);
               }
            }

            int total = 0;
            for (BoundedRangeModel model : sliderModelList) {
               total += model.getValue();
            }
            //!! System.out.printf("Total = %.0f%n", (double)total * 100 / LinkedSliders2.SLIDER_MAX_VALUE);

            internalChange = false;
         }
      }

   }

}

编辑为让SliderGroup2使用BoundedRangeModels列表而不是JSliders。