为什么 Swing 框架有时没有在下面打开我附加了我的代码，任何人都可以帮助我为什么会这样？

Question

Here i Attached my Code: I'm now Currently working on Music Player that i want to create so i coded on Swing FrameWork this code is works fine before adding two buttons named Previous button and Next Play Button after adding those buttons swing frame is not opening even i tried by commenting newly added lines(Previous button and Next button) but that didn't help me

//Main Method
import javax.swing.JFrame;
import javax.swing.SwingUtilities;`

public class App{
public static void main(String args[]){
    SwingUtilities.invokeLater(new Runnable() { //To make Robust
        public void run(){  //Run Method
            new MainFrame();        }
    });
}
}
//Frame Method
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import java.awt.FlowLayout;
public class MainFrame extends JFrame{
private JButton Play,Previous,Next;
private JTextArea textArea;
public MainFrame(){
    super("Hello World"); //Inherit that Jframe

    try{

    setLayout(new BorderLayout()); //Setting Layout
    setLayout(new FlowLayout());





    Play=new JButton("Play"); //Creating Object for Button

    Previous=new JButton("Previous");

    Next=new JButton("Next");



    textArea=new JTextArea();//Creating object for JTextArea

    Play.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent l) {
            textArea.append("Song plays\n");//Print Song Plays
        }
    });


Previous.addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent l){
        textArea.append("Previous Song\n");
    }
});

Next.addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent l){
        textArea.append("Next Song\n");
    }
});
//Adding TextArea and Buttons to Frame
    add(Play,FlowLayout.CENTER);//Adding to Frame
    add(textArea,FlowLayout.LEADING);//Adding to Frame
    add(Previous,FlowLayout.LEFT);
    add(Next,FlowLayout.RIGHT);

  


    setSize(800,800);//Size for Frame
    setResizable(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
}
catch( Exception e){
e.printStackTrace();
}
}
}

Answer 1

Oracle has a helpful tutorial, Creating a GUI With Swing . Skip the Learning Swing with the NetBeans IDE section. Pay particular attention to the Laying Out Components Within a Container section.

I went ahead and created the following GUI.

When creating a Swing GUI, you add Swing components to a JPanel or JScrollPane . You add JPanels and/or JScrollPanes to your JFrame . This helps keep your code organized.

Swing layout managers make creating a GUI simple. You add Swing components to one or more JPanels , add the JPanels to the JFrame , and pack the JFrame .

The only "trick" I used was copying the preferred size of the largest JButton to the other JButtons . This makes the GUI look better.

Here's the complete runnable code.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class MusicPlayer implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new MusicPlayer());
    }

    private JTextArea textArea;

    @Override
    public void run() {
        JFrame frame = new JFrame("Music Player");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(createTextArea(), BorderLayout.CENTER);
        frame.add(createButtonPanel(), BorderLayout.SOUTH);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JScrollPane createTextArea() {
        JPanel panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

        textArea = new JTextArea(10, 40);
        panel.add(textArea, BorderLayout.CENTER);

        JScrollPane scrollPane = new JScrollPane(panel);

        return scrollPane;
    }

    private JPanel createButtonPanel() {
        JPanel panel = new JPanel(new FlowLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

        JButton previousButton = new JButton("Previous");
        previousButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                textArea.append("Previous Song\n");
            }
        });
        panel.add(previousButton);

        JButton playButton = new JButton("Play");
        playButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                textArea.append("Song plays\n");// Print Song Plays
            }
        });
        panel.add(playButton);

        JButton nextButton = new JButton("Next");
        nextButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                textArea.append("Next Song\n");
            }
        });
        panel.add(nextButton);

        // Make the buttons the same size
        Dimension d = previousButton.getPreferredSize();
        playButton.setPreferredSize(d);
        nextButton.setPreferredSize(d);

        return panel;
    }

}