Question

我想要显示一棵树。但树没有出现。有什么问题？

主：

package scanner_parser;
public class Main {
    public static void main(String[] args) {
        Oberflaeche gui = new Oberflaeche();
        gui.setVisible(true);
    }
}

GUI：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.*;
import javax.swing.*;

public class Oberflaeche extends JFrame implements ActionListener {

    private JPanel cp, top, bottom;
    private JTextField eingabefeld = new JTextField();
    private JButton button = new JButton("Darstellen");
    private JMenuBar menubar = new JMenuBar();
    private JMenu menu;
    private JMenuItem anleitung, beenden, bEins, bZwei, bDrei, bVier;
    private Baum baum = new Baum();

    public Oberflaeche() {
        this.setTitle("Funktionsparser");
        this.setSize(900, 700);
        this.setLocation(300, 100);
        this.setResizable(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        initMenu();

        cp = (JPanel) this.getContentPane();
        cp.setLayout(new BorderLayout(2, 1));
        top = new JPanel();
        top.setLayout(null);
        top.setBounds(0, 0, getWidth(), 50);
        top.setBackground(Color.white);

        bottom = new JPanel();
        bottom.setBounds(0, 50, getWidth(), getHeight() - 50);
        bottom.setBackground(Color.white);

        eingabefeld.setBounds(10, 10, getWidth() - 120, 30);
        button.setBounds(getWidth() - 110, 10, 100, 30);
        button.addActionListener(this);

        top.add(button);
        top.add(eingabefeld);
        cp.add(top);
        cp.add(bottom);
    }

    // Initialise Menu

    private void initMenu() {
        menu = new JMenu("Datei");
        anleitung = new JMenuItem("Anleitung");
        anleitung.addActionListener(this);

        menu.add(anleitung);
        beenden = new JMenuItem("Beenden");
        beenden.addActionListener(this);

        menu.add(beenden);
        menubar.add(menu);

        menu = new JMenu("Beispiele");

       // Load some example functions into the textfield

        bEins = new JMenuItem("<html>3 * x</html>");
        bEins.addActionListener(this);
        menu.add(bEins);

        bZwei = new JMenuItem("<html>3 * x<sup>2</sup></html>");
        bZwei.addActionListener(this);
        menu.add(bZwei);

        bDrei = new JMenuItem("<html>3 * ( x<sup>2</sup> + 1 )</html>");
        bDrei.addActionListener(this);
        menu.add(bDrei);

        bVier = new JMenuItem("<html>3 * ( x<sup>2</sup> + x<sup>4</sup> + 1 )</html>");
        bVier.addActionListener(this);
        menu.add(bVier);

        menubar.add(menu);

        this.setJMenuBar(menubar);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        Object s = e.getSource();

        if (s == anleitung) {

        }

       // This should add the tree (baum) but it does not appear.


        if (s == button) {
            FuncParser.theParser().parse(eingabefeld.getText());
            FuncParser.theParser().getWurzel().print();
            bottom.add(baum);
        }
        if (s == beenden) {
            System.exit(0);
        }
        if (s == bEins) {
            eingabefeld.setText("3*x");
        }
        if (s == bZwei) {
            eingabefeld.setText("3*x^2");
        }
        if (s == bDrei) {
            eingabefeld.setText("3*(x^2+1)");
        }
        if (s == bVier) {
            eingabefeld.setText("3*(x^2+x^4+1)");
        }
    }
}

树类：

import java.awt.*;
import javax.swing.JPanel;

public class Baum extends JPanel {

    private final int radius = 20;
    private final int paddingY = 75;

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        System.out.println("test");
        displayBaum(g, FuncParser.theParser().getWurzel(), getWidth() / 2, 100, 20 + getWidth() / 4);
    }

    private void displayBaum(Graphics g, Knoten k, int x, int y, int paddingX) {
        g.drawOval(x - radius, y - radius, 2 * radius, 2 * radius);
        g.drawString(k.getDaten(), x - 4, y + 4);

        if (k.getLinks() != null) {
            displayKante(g, x - paddingX, y + paddingY, x, y);
            displayBaum(g, k.getLinks(), x - paddingX, y + paddingY, 10 + paddingX / 2);
            displayKante(g, x + paddingX, y + paddingY, x, y);
            displayBaum(g, k.getLinks(), x + paddingX, y + paddingY, 10 + paddingX / 2);
        }
    }

    private void displayKante(Graphics g, int x1, int y1, int x2, int y2) {
        double d = Math.sqrt(paddingY * paddingY + (x2 - x1) * (x2 - x1));
        int x11 = (int) (x1 - radius * (x1 - x2) / d);
        int y11 = (int) (y1 - radius * (y1 - y2) / d);
        int x21 = (int) (x2 + radius * (x1 - x2) / d);
        int y21 = (int) (y2 + radius * (y1 - y2) / d);
        g.drawLine(x11, y11, x21, y21);
    }
}

文字＆＃34;测试＆＃34;每次缩放窗口时都会出现在控制台中。这意味着将调用该函数，但树不会出现在内容窗格中。也许它在底下？我现在不知道为什么。如果您有任何想法，请提供帮助。

Answer 1

将碎片缩减为可编辑状态，我得到以下结果。特别是，

不要使用null布局;该示例使用BorderLayout的默认JFrame和FlowLayout的{{1}}。
使用JTextField构造函数，您可以在列中指定字段的宽度。
覆盖getPreferredSize()以建立绘图区域的初始几何图形，并相对于其当前尺寸绘制。
在event dispatch thread上构建和操作仅的Swing GUI对象。

在Panel equals()中使用==优先于ActionListener。

import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JPanel; import javax.swing.JTextField; /** * @See https://stackoverflow.com/a/38215252/230513 */ public class Main { public static void main(String[] args) { EventQueue.invokeLater(() -> { Oberflaeche gui = new Oberflaeche(); gui.setVisible(true); }); } private static class Baum extends JPanel { private final int radius = 20; private final int paddingY = 75; @Override public void paintComponent(Graphics g) { super.paintComponent(g); g.drawString("Hello", 16, 16); displayKante(g, 0, 0, getWidth(), getHeight()); } @Override public Dimension getPreferredSize() { return new Dimension(329, 240); } private void displayKante(Graphics g, int x1, int y1, int x2, int y2) { double d = Math.sqrt(paddingY * paddingY + (x2 - x1) * (x2 - x1)); int x11 = (int) (x1 - radius * (x1 - x2) / d); int y11 = (int) (y1 - radius * (y1 - y2) / d); int x21 = (int) (x2 + radius * (x1 - x2) / d); int y21 = (int) (y2 + radius * (y1 - y2) / d); g.drawLine(x11, y11, x21, y21); } } private static class Oberflaeche extends JFrame implements ActionListener { private JPanel top, bottom; private JTextField eingabefeld = new JTextField(20); private JButton button = new JButton("Darstellen"); private JMenuBar menubar = new JMenuBar(); private JMenu menu; private JMenuItem anleitung, beenden, bEins, bZwei, bDrei, bVier; private Baum baum = new Baum(); public Oberflaeche() { this.setDefaultCloseOperation(EXIT_ON_CLOSE); this.setTitle("Funktionsparser"); initMenu(); top = new JPanel(); top.setBackground(Color.white); top.add(button); top.add(eingabefeld); button.addActionListener(this); bottom = new JPanel(); bottom.setBackground(Color.white); bottom.add(new JLabel("Label text.")); this.add(top, BorderLayout.NORTH); this.add(baum); this.add(bottom, BorderLayout.SOUTH); this.pack(); this.setLocationRelativeTo(null); } // Initialise Menu private void initMenu() { menu = new JMenu("Datei"); anleitung = new JMenuItem("Anleitung"); anleitung.addActionListener(this); menu.add(anleitung); beenden = new JMenuItem("Beenden"); beenden.addActionListener(this); menu.add(beenden); menubar.add(menu); menu = new JMenu("Beispiele"); // Load some example functions into the textfield bEins = new JMenuItem("<html>3 * x</html>"); bEins.addActionListener(this); menu.add(bEins); bZwei = new JMenuItem("<html>3 * x2</html>"); bZwei.addActionListener(this); menu.add(bZwei); bDrei = new JMenuItem("<html>3 * ( x2 + 1 )</html>"); bDrei.addActionListener(this); menu.add(bDrei); bVier = new JMenuItem("<html>3 * ( x2 + x4 + 1 )</html>"); bVier.addActionListener(this); menu.add(bVier); menubar.add(menu); this.setJMenuBar(menubar); } @Override public void actionPerformed(ActionEvent e) { Object s = e.getSource(); if (s == anleitung) { System.out.println(anleitung); } if (s == button) { System.out.println(button); } if (s == beenden) { System.exit(0); } if (s == bEins) { eingabefeld.setText("3*x"); } if (s == bZwei) { eingabefeld.setText("3*x^2"); } if (s == bDrei) { eingabefeld.setText("3*(x^2+1)"); } if (s == bVier) { eingabefeld.setText("3*(x^2+x^4+1)"); } } } }

Answer 2

您要将两个面板添加到内容窗格的中心cp，并且永远不会添加baum。在面板上使用约束如下：

cp.add(top, BorderLayout.NORTH);
cp.add(baum, BorderLayout.CENTER);
cp.add(bottom, BorderLayout.SOUTH);

绘图树不可见;也许布局问题

2 个答案: