当尝试使用 class SpringUtilities 制作 CompactGrid 时，'no such child' 在 java swing 中意味着什么

Question

所以我尝试制作一个简单的 java swing 程序，我没有完成程序，但我想在执行功能部分之前先看看它的外观，这是我的代码：

import layouts.SpringUtilities;

import javax.swing.*;
import layouts.SpringUtilities;


public class FactorialCalculatorFrame extends JFrame {

    public FactorialCalculatorFrame(){
        JPanel panel = new JPanel();
        panel.setLayout(new SpringLayout());


        JTextField brojText = new JTextField();
        brojText.setColumns(10);
        panel.add(new JLabel("Broj:", SwingConstants.RIGHT));
        panel.add(brojText);


        JButton start = new JButton("Start");

        panel.add(new JLabel("Pokreni izracun:",SwingConstants.RIGHT));
        panel.add(start);


        JProgressBar napredakProgressBar = new JProgressBar();

        add(new JLabel("Napredak:", SwingConstants.RIGHT));
        add(napredakProgressBar);

        JLabel rezultat = new JLabel("Rezultat:");
        JLabel ispisiRez = new JLabel("");

        add(new JLabel("Rezultat:", SwingConstants.RIGHT));
        add(ispisiRez);


        start.addActionListener((e)->{
            try {
                int number = Integer.parseInt(brojText.getText());

                //reset GUI components
                napredakProgressBar.setValue(0);
                start.setEnabled(false);
                ispisiRez.setText("");

                //schedule for execution on one of working threads
                new primeNumberJavaSwingApp().execute();

                            } catch (Exception ex) {
                ex.printStackTrace();
            }
        });

        SpringUtilities.makeCompactGrid(panel,4, 2, 0, 0, 5, 5);

        add(panel);
    }
    public static void main(String[] args){
        FactorialCalculatorFrame frame = new FactorialCalculatorFrame();
        frame.setVisible(true);
    }

    public class primeNumberJavaSwingApp extends SwingWorker<Long, Integer> {
        @Override
        protected Long doInBackground() throws Exception {
            Long l = (long)3.2;
return l;}}}

the Exception that occurs is this Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: No such child: 4
at layouts.SpringUtilities.makeCompactGrid(SpringUtilities.java:190)
at FactorialCalculatorFrame.<init>(FactorialCalculatorFrame.java:55)

为什么会出现这种情况，我做错了什么？

我还使用从 Oracle 复制的 SpringUtilities class。非常感谢任何帮助！

Answer 1

我从 here 下载了 class SpringUtilities 的源代码。

您的问题是您没有将所有组件添加到 panel。当您应该调用 panel.add() 时，您调用了 add()。因此，您只将 4 个组件添加到 panel 而不是 8 个。因此出现错误消息。

我还添加了对 class JFrame 方法 pack() 的调用，以便使 JFrame 足够大以显示它包含的所有组件。

这是你的代码和我的修正：

import layout.SpringUtilities; // in your code this import is added twice

import javax.swing.*;

public class FactorialCalculatorFrame extends JFrame {
    public FactorialCalculatorFrame() {
        setDefaultCloseOperation(EXIT_ON_CLOSE); // I added this line
        JPanel panel = new JPanel();
        panel.setLayout(new SpringLayout());

        JTextField brojText = new JTextField();
        brojText.setColumns(10);
        panel.add(new JLabel("Broj:", SwingConstants.RIGHT));
        panel.add(brojText);

        JButton start = new JButton("Start");

        panel.add(new JLabel("Pokreni izracun:",SwingConstants.RIGHT));
        panel.add(start);

        JProgressBar napredakProgressBar = new JProgressBar();

        panel.add(new JLabel("Napredak:", SwingConstants.RIGHT)); // change here
        panel.add(napredakProgressBar); // change here

        JLabel rezultat = new JLabel("Rezultat:");
        JLabel ispisiRez = new JLabel("");

        panel.add(new JLabel("Rezultat:", SwingConstants.RIGHT));
        panel.add(ispisiRez);

        start.addActionListener((e)->{
            try {
                int number = Integer.parseInt(brojText.getText());

                //reset GUI components
                napredakProgressBar.setValue(0);
                start.setEnabled(false);
                ispisiRez.setText("");

                //schedule for execution on one of working threads
                new primeNumberJavaSwingApp().execute();

                            } catch (Exception ex) {
                ex.printStackTrace();
            }
        });
        SpringUtilities.makeCompactGrid(panel, 4, 2, 0, 0, 5, 5);
        add(panel);
    }

    public static void main(String[] args){
        FactorialCalculatorFrame frame = new FactorialCalculatorFrame();
        frame.pack(); // I added this line
        frame.setLocationRelativeTo(null); // I added this line
        frame.setVisible(true);
    }

    public class primeNumberJavaSwingApp extends SwingWorker<Long, Integer> {
        @Override
        protected Long doInBackground() throws Exception {
            Long l = (long) 3.2;
            return l;
        }
    }
}

这是 JFrame 上面代码运行时的屏幕截图。

当尝试使用 class SpringUtilities 制作 CompactGrid 时，'no such child' 在 java swing 中意味着什么

What 'no such child' means in java swing when trying to makeCompactGrid with class SpringUtilities

java

swing

swingworker