嵌套的 JSplitPane 问题； setPreferredSize 和 setDividerLocation 不起作用答案

【问题标题】：Nested JSplitPane problem; setPreferredSize and setDividerLocation not working嵌套的 JSplitPane 问题； setPreferredSize 和 setDividerLocation 不起作用
【发布时间】：2021-06-17 19:46:38
【问题描述】：

我有一个包含两个 JPanel 的 JFrame，一个是 menuBar，另一个是框架的主体。我希望将主体分成三个 JScrollPanes，以便它们可以扩展或缩小。我嵌套了两个 JSplitPanes 来实现这一点。我的问题是我为 JSplitPanes 定义的 setDividerLocation 和 setPreferredSize 不起作用。我尝试了 resetToPreferredSizes，这对 JFrame 也没有明显的影响。

这是我的代码：

    public class HomeView {
    private JFrame frame;
    private JPanel top;
    private JPanel center;
    private JPanel bottom;

    private JScrollPane lPane;
    private JScrollPane cPane;
    private JScrollPane rPane;

    private JSplitPane cr;
    private JSplitPane lcr;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    HomeView window = new HomeView();
                    window.frame.setVisible(true);
                    window.cr.resetToPreferredSizes();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    
    public HomeView() {
        initialize();
    }

    private void initialize() {
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        frame.setSize(Constants.pcSize);
        frame.setBackground(Color.BLACK);

        top = new JPanel();
        top.setBackground(P.light);

        center = new JPanel();
        center.setBackground(P.mix);

        bottom = new JPanel();
        bottom.setBackground(P.lightGrey);

        GroupLayout groupLayout = new GroupLayout(frame.getContentPane());
        groupLayout.setHorizontalGroup(groupLayout.createParallelGroup(Alignment.TRAILING)
                .addGroup(groupLayout.createSequentialGroup().addGap(P.Xa)
                        .addComponent(top, GroupLayout.DEFAULT_SIZE, C.mWidth, Short.MAX_VALUE).addGap(P.Xa))
                .addGroup(groupLayout.createSequentialGroup().addGap(P.Xb)
                        .addComponent(center, GroupLayout.DEFAULT_SIZE, C.pWidth, Short.MAX_VALUE).addGap(P.Xb))
                .addGroup(groupLayout.createSequentialGroup().addGap(P.Xc)
                        .addComponent(bottom, GroupLayout.DEFAULT_SIZE, C.bWidth, Short.MAX_VALUE).addGap(P.Xc)));
        groupLayout.setVerticalGroup(groupLayout.createParallelGroup(Alignment.LEADING)
                .addGroup(groupLayout.createSequentialGroup().addGap(P.H1)
                        .addComponent(top, GroupLayout.DEFAULT_SIZE, C.mHeight, Short.MAX_VALUE).addGap(P.H2)
                        .addComponent(center, GroupLayout.DEFAULT_SIZE, C.pHeight, Short.MAX_VALUE).addGap(P.H3)
                        .addComponent(bottom, GroupLayout.DEFAULT_SIZE, C.bHeight, Short.MAX_VALUE).addGap(P.HZ)));

        lPane = new JScrollPane();
        lPane.setPreferredSize(new Dimension(C.lWidth, C.lHeight));

        cPane = new JScrollPane();
        cPane.setPreferredSize(new Dimension(C.cWidth, C.cHeight));

        rPane = new JScrollPane();
        rPane.setPreferredSize(new Dimension(C.rWidth, C.rHeight));

        cr = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, cPane, rPane);
        cr.setPreferredSize(new Dimension(C.crWidth, C.crHeight));
        cr.setDividerSize(P.D);
        cr.setDividerLocation(0.8125);
        cr.setBorder(BorderFactory.createCompoundBorder());
        cr.resetToPreferredSizes();

        lcr = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, lPane, cr);
        lcr.setDividerSize(P.D);
        lcr.setDividerLocation(0.2);
        lcr.setBorder(BorderFactory.createCompoundBorder());
        lcr.resetToPreferredSizes();

        GroupLayout layoutC = new GroupLayout(center);
        layoutC.setHorizontalGroup(
                layoutC.createParallelGroup(Alignment.LEADING).addGroup(layoutC.createSequentialGroup().addGap(0)
                        .addComponent(lcr, GroupLayout.DEFAULT_SIZE, C.lcrWidth, GroupLayout.DEFAULT_SIZE).addGap(0)));
        layoutC.setVerticalGroup(layoutC.createParallelGroup(Alignment.LEADING).addGroup(layoutC.createSequentialGroup()
                .addGap(0).addComponent(lcr, GroupLayout.DEFAULT_SIZE, C.lcrHeight, GroupLayout.DEFAULT_SIZE).addGap(0)));
        center.setLayout(layoutC);

        frame.getContentPane().setLayout(groupLayout);
        frame.pack();
    }
}

我的 C 和 P 类只是存储值。

public class P {

    public static int Xa = 0;
    public static int Xb = 1;
    public static int Xc = 1;

    public static int H1 = 0;
    public static int H2 = 1;
    public static int H3 = 1;
    public static int HZ = 0;
    
    public static int D = 4;
    
    public static Color white = new Color(255, 255, 255);
    public static Color black = new Color(0, 0, 0);
    public static Color dark = new Color(60, 60, 60);
    public static Color light = new Color(220, 220, 255);
    public static Color mix = new Color(150, 180, 210);
    public static Color javaDefault = new Color(204, 204, 204);
    public static Color distinct = new Color(180, 55, 55);
    public static Color ciel = new Color(0, 55, 55);
    public static Color darkGrey = new Color(88, 88, 88);
    public static Color lightGrey = new Color(230, 230, 230);
    
}
public class C {
    public static Dimension pcSize = Toolkit.getDefaultToolkit().getScreenSize();

    private static String s = File.separator;
    public static File defaultFile = new File("metadata" + s + "default");
    public static File userFile = new File("metadata" + s + "user");

    private static int tolR = 8;
    private static int tolL = 8;
    private static int tolT = 31;
    private static int tolB = 8;

    public static int pcWidth = pcSize.width;
    public static int pcHeight = pcSize.height;

    public static int sHeight = pcHeight - tolT - tolB;
    public static int sWidth = pcWidth - tolR - tolL;

    public static int mHeight = (int) ((double) (sHeight * 0.062));
    public static int mWidth = sWidth - (2 * P.Xa);
    
    public static int bHeight = (int) ((double) (sHeight * 0.0345));
    public static int bWidth = sWidth - (2 * P.Xc);
    
    public static int pHeight = sHeight - P.H1 - mHeight - P.H2 - P.H3 - bHeight - P.HZ;
    public static int pWidth = sWidth - (2 * P.Xb);
    
    public static int lHeight = pHeight;
    public static int lWidth = (int)((double) (sWidth * 0.2));
    
    public static int cHeight = pHeight;
    public static int cWidth = (int)((double) (sWidth * 0.65));
    
    public static int rHeight = pHeight;
    public static int rWidth = sWidth - lWidth - cWidth;
    
    public static int crWidth = cWidth + rWidth;
    public static int crHeight = cHeight;
    
    public static int lcrWidth = pWidth;
    public static int lcrHeight = pHeight;
}

我只是添加了它们，以防有人想尝试运行我的代码。

我的结果：这不是预期的首选大小或分隔线位置。我尝试删除它们，输出没有变化。我希望有人能帮我找出哪里出了问题？？？？。耐心等待。

【问题讨论】：

见：What should I do when someone answers my question

标签： java swing jsplitpane

【解决方案1】：

cr.setDividerLocation(0.8125);

setDividerLocation( double ) 方法仅适用于“已实现”的框架。也就是说，在调用布局管理器之前，组件没有大小。因此，在调用setDividerLocation() 方法之前，您需要在框架上调用pack() 或setVisible(true)。

但是，这并不是一个好的解决方案，因为您的课程设计不正确。你的HomeView 类不应该对框架一无所知。它应该是一个独立的组件，就像可以添加到任何框架或对话框的 JLabel 或 JButton 一样。框架应在您的 main() 方法中创建。

那么更好的解决方案是在类的构造函数中将代码包装在SwingUtilities.invokeLater() 中，以将代码添加到Event Dispatch Thread (EDT) 的末尾，以确保代码在框架可见后执行。类似的东西

SwingUtilities.invokeLater(new Runnable()
{
    public void run()
    {
        cr.setDividerLocation(0.8125);
    }
});

阅读 How to Use Split Panes 上的 Swing 教程。 SplitPaneDemo 代码将演示如何更好地构建您的代码。

【讨论】：