Java GUI重绘错误？

Question

这是一个棘手的问题 - 我有一个生成 JTextFields 的 JFrame。当我从生成 2 个 JTextFields 到生成 12 个 JTextfields(例如)时，我看到一些错误，其中最后有一个额外的不同大小的 JTextField。这似乎是重绘错误。

Main.java代码:

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

public class Main {
    public static Display display = new Display();

    public static void main(String[] args) {
        display.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        display.setVisible(true);
    }
}

Display.java代码:

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

public class Display extends JFrame {
    final int FRAME_WIDTH = 820;
    final int FRAME_HEIGHT = 700;
    final int X_OFFSET = 40;
    final int Y_OFFSET = 40;

    final int GRAPH_OFFSETX = 35;
    final int GRAPH_OFFSETY = 60;
    final int GRAPH_WIDTH = 500;
    final int GRAPH_HEIGHT = 500;
    final int GRAPH_INTERVAL = 20;

    JButton submit;
    JTextField top;
    JTextField bottom;
    JTextField numPoint;
    JPanel bpanel;
    JPanel points;

    int maxPoints;

    public Display() {
        init();
    }

    public void init() {
        setBackground(Color.WHITE);
        setLocation(X_OFFSET, Y_OFFSET);
        setSize(FRAME_WIDTH, FRAME_HEIGHT);
        setTitle("Geometric Transformations");
        getContentPane().setLayout(null);
        setDefaultLookAndFeelDecorated(true);

        top = new JTextField();    // parameter is size of input characters
        top.setText("1 2 3");
        top.setBounds(590, 150, 120, 25);

        bottom = new JTextField();    // parameter is size of input characters
        bottom.setText("5 6 7");
        bottom.setBounds(590, 200, 120, 25);

        numPoint = new JTextField();
        numPoint.setText("Number of Points?");
        numPoint.setBounds(550,200,200,25);
        this.add(numPoint);

        SubmitButton submit = new SubmitButton("Submit");
        submit.setBounds(570, 250, 170, 25);

        bpanel = new JPanel(new GridLayout(2,3));
        bpanel.add(top);
        bpanel.add(bottom);
        bpanel.add(submit);

        points = new JPanel(new GridLayout(2,2));
        points.setBounds(540,250,265,60);
        this.add(points);

        bpanel.setBounds(550,100,200,70);
        this.add(bpanel, BorderLayout.LINE_START);

        Component[] a = points.getComponents();
        System.out.println(a.length);
        repaint();
    }

    public void paint(Graphics g) {
        super.paint(g);
        g.setColor(Color.WHITE);
        g.fillRect(100, 100, 20, 30);
        g.setColor(Color.BLACK);
        genGraph(g, GRAPH_OFFSETX, GRAPH_OFFSETY, GRAPH_WIDTH, GRAPH_HEIGHT, GRAPH_INTERVAL);
    }

    public void genGraph (Graphics g, int x, int y, int width, int height, int interval) {
        // draw background
        int border = 5;
        g.setColor(Color.BLACK);
        width = width - (width % interval);
        height = height - (height % interval);
        for (int col=x; col <= x+width; col+=interval) {
            g.drawLine(col, y, col, y+height);
        }
        for (int row=y; row <= y+height; row+=interval) {
            g.drawLine(x, row, x+width, row);
        }
    }
    class SubmitButton extends JButton implements ActionListener {

        public SubmitButton(String title){
            super(title);
            addActionListener(this);
            this.setVisible(true);
        }
        public void actionPerformed(ActionEvent e) {
            maxPoints = Integer.parseInt(numPoint.getText()) * 2;

            points.removeAll();

            for (int i=0; i<maxPoints; i++) {
                JTextField textField = new JTextField();
                points.add(textField);
            }
            points.validate();        // necessary when adding components to a JPanel
            // http://stackoverflow.com/questions/369823/java-gui-repaint-problem-solved
            // What to Check:
            // Things between commas are either spaces (which will be stripped later)
            // or numbers!

            // Pairs must match up!
        }
    }
}

Answer 1

新组件在之前的组件上重新绘制。我在 points.validate(); 之后添加了 points.repaint();，问题就解决了。