java - 如果用户移动了分隔线的位置，如何让 JSplitPane 保持相同的比例位置

Question

我无法让 JSplitPane 在调整其容器大小时保持相同的相对位置。如果假定拆分 Pane 具有固定位置，则一切正常。我可以使用下面显示的代码使分隔线位置保持接近相同的相对位置，但是当调整 JFrame 大小时分隔线向左移动。如果缓慢调整 JFrame 的大小，偏移会更大。如果 JFrame 变小或变大，则向左移动。

如何让分隔线保持在完全相同的比例位置？

这是 GUI 最初的样子。

这是几次调整大小后的样子。

这就是代码的样子。此尝试基于此处提供的信息:

JSplitPane splitting 50% precisely

JSplitPane SetDividerLocation Problem

https://docs.oracle.com/javase/tutorial/uiswing/components/splitpane.html

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSplitPane;

public class Example {

    public static void main(String[] args) {
        new Example().showGui();
    }

    private void showGui() {
        // create the jframe
        JFrame jFrame = new JFrame();
        jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jFrame.setSize(400, 200);
        // create the left and right panels
        JPanel left = new JPanel();
        left.setBackground(Color.yellow);
        JPanel right = new JPanel();
        right.setBackground(Color.orange);
        ResizableSplitPane split = new ResizableSplitPane(JSplitPane.HORIZONTAL_SPLIT, left, right, jFrame);
        jFrame.getContentPane().add(split);
        // show the gui
        jFrame.setVisible(true);
    }

    public class ResizableSplitPane extends JSplitPane {

        //
        // instance variables
        //

        private boolean painted;

        private double defaultDividerLocation;

        private ResizableSplitPane resizableSplitPane = this;

        private double currentDividerLocation;

        private Component first;

        private Component second;

        private boolean dividerPositionCaptured = false;

        //
        // constructors
        //

        public ResizableSplitPane(int splitType, Component first, Component second, Component parent) {
            this(splitType, first, second, parent, 0.5);
        }

        public ResizableSplitPane(int splitType, Component first, Component second, Component parent, double defaultDividerLocation) {
            super(splitType, first, second);
            this.defaultDividerLocation = defaultDividerLocation;
            this.currentDividerLocation = defaultDividerLocation;
            this.setResizeWeight(defaultDividerLocation);
            this.first = first;
            this.second = second;
            parent.addComponentListener(new DividerLocator());
            first.addComponentListener(new DividerMovedByUserComponentAdapter());
        }

        //
        // trivial getters and setters
        //

        public double getDefaultDividerLocation() {
            return defaultDividerLocation;
        }

        public void setDefaultDividerLocation(double defaultDividerLocation) {
            this.defaultDividerLocation = defaultDividerLocation;
        }

        //
        // implementation
        //

        @Override
        public void paint(Graphics g) {
            super.paint(g);
            if (!painted) {
                painted = true;
                this.setDividerLocation(currentDividerLocation);
            }
            dividerPositionCaptured = false;
        }

        private class DividerLocator extends ComponentAdapter {
            @Override
            public void componentResized(ComponentEvent e) {
                setDividerLocation(currentDividerLocation);
            }
        }

        private class DividerMovedByUserComponentAdapter extends ComponentAdapter {
            @Override
            public void componentResized(ComponentEvent e) {
                if (dividerPositionCaptured == false) {
                    dividerPositionCaptured = true;
                    currentDividerLocation = (double) first.getWidth() / (double) (first.getWidth() + second.getWidth());
                    System.out.println(currentDividerLocation);
                }
            }
        }

    }

}

Answer 1

• 这是我的尝试:
  • 重写JSplitPane父组件的doLayout方法，在JSplitPane缩放完成后，调整JSplitPane的位置分隔线。

import java.awt.*;
import java.awt.event.*;
import java.math.BigDecimal;
import javax.swing.*;

public class Example2 {
  public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      f.getContentPane().add(new Example2().makeUI());
      f.setSize(400, 240);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
  private JComponent makeUI() {
    JPanel p = new JPanel(new GridLayout(0, 1, 0, 0));

    JPanel left1 = new JPanel();
    left1.setBackground(Color.YELLOW);
    JPanel right1 = new JPanel();
    right1.setBackground(Color.ORANGE);
    JSplitPane split1 = new ResizableSplitPane(
        JSplitPane.HORIZONTAL_SPLIT, left1, right1, p);
    p.add(split1);

    JPanel left2 = new JPanel();
    left2.setBackground(Color.YELLOW);
    JPanel right2 = new JPanel();
    right2.setBackground(Color.ORANGE);
    JSplitPane split2 = new JSplitPane(
        JSplitPane.HORIZONTAL_SPLIT, left2, right2);
    p.add(new SplitPaneWrapper(split2));

    return p;
  }
}

class ResizableSplitPane extends JSplitPane {
  //
  // instance variables
  //

  private boolean painted;

  private double defaultDividerLocation;

  private ResizableSplitPane resizableSplitPane = this;

  private double currentDividerLocation;

  private Component first;

  private Component second;

  private boolean dividerPositionCaptured = false;

  //
  // constructors
  //

  public ResizableSplitPane(int splitType, Component first, Component second, Component parent) {
    this(splitType, first, second, parent, 0.5);
  }

  public ResizableSplitPane(int splitType, Component first, Component second, Component parent, double defaultDividerLocation) {
    super(splitType, first, second);
    this.defaultDividerLocation = defaultDividerLocation;
    this.currentDividerLocation = defaultDividerLocation;
    this.setResizeWeight(defaultDividerLocation);
    this.first = first;
    this.second = second;
    parent.addComponentListener(new DividerLocator());
    first.addComponentListener(new DividerMovedByUserComponentAdapter());
  }

  //
  // trivial getters and setters
  //

  public double getDefaultDividerLocation() {
    return defaultDividerLocation;
  }

  public void setDefaultDividerLocation(double defaultDividerLocation) {
    this.defaultDividerLocation = defaultDividerLocation;
  }

  //
  // implementation
  //

  @Override
  public void paint(Graphics g) {
    super.paint(g);
    if (!painted) {
      painted = true;
      this.setDividerLocation(currentDividerLocation);
    }
    dividerPositionCaptured = false;
  }

  private class DividerLocator extends ComponentAdapter {
    @Override
    public void componentResized(ComponentEvent e) {
      setDividerLocation(currentDividerLocation);
    }
  }

  private class DividerMovedByUserComponentAdapter extends ComponentAdapter {
    @Override
    public void componentResized(ComponentEvent e) {
      if (dividerPositionCaptured == false) {
        dividerPositionCaptured = true;
        currentDividerLocation = (double) first.getWidth() / (double)(first.getWidth() + second.getWidth());
        System.out.println(currentDividerLocation);
      }
    }
  }

}

class SplitPaneWrapper extends JPanel {
  private final JSplitPane splitPane;
  protected SplitPaneWrapper(JSplitPane splitPane) {
    super(new BorderLayout());
    this.splitPane = splitPane;
    splitPane.setResizeWeight(.5);
    add(splitPane);
  }
  private static int getOrientedSize(JSplitPane sp) {
    return sp.getOrientation() == JSplitPane.VERTICAL_SPLIT
           ? sp.getHeight() - sp.getDividerSize()
           : sp.getWidth()  - sp.getDividerSize();
  }
  @Override public void doLayout() {
    int size = getOrientedSize(splitPane);
    double d = splitPane.getDividerLocation() / (double) size;
    BigDecimal bd = new BigDecimal(d).setScale(2, BigDecimal.ROUND_HALF_UP);
    super.doLayout();
    if (splitPane.isShowing()) {
      EventQueue.invokeLater(() -> {
        int s = getOrientedSize(splitPane);
        int iv = (int)(.5 + s * bd.doubleValue());
        splitPane.setDividerLocation(iv);
      });
    }
  }
}