java - 对 jlist 的元素进行排序

Question

我试图在按下排序按钮时对 JList 进行排序，但我不知道如何排序。这是我的代码:

歌曲类:

package song;

public class Song implements Comparable<Song>{
    private String name;
    private String artist;

    public Song(String name, String artist){
        this.name = name;
        this.artist = artist;
    }

    public String getName(){
        return name;
    }

    public String getArtist(){
        return artist;
    }

    public void setArtist(String artist){
        this.artist = artist;
    }

    public void setName(String name){
        this.name = name;
    }

    public int compareTo(Song s){
        return this.name.compareTo(s.getName());
    }

    public String toString(){
        return name + " " + artist;
    }
}

列表模型:

package song;

import java.util.ArrayList;
import java.util.Collections;

import javax.swing.AbstractListModel;

public class ListModel extends AbstractListModel{
    ArrayList<Song> songs;

    public ListModel(ArrayList<Song> array){
        songs = array;
    }

    public int getSize(){
        return songs.size();
    }

    public Object getElementAt(int index){
        return (Song)songs.get(index);
    }

    public ArrayList<Song> getSongList(){
        return songs;
    }

    public void setList(ArrayList<Song> array){
        this.songs = array;
    }

    public void getSortedList(ArrayList<Song> array){
        Collections.sort(array);
        songs = array;
    }
}

应用类:

    package song;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Collections;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;

public class App extends JFrame{
    JFrame frame;
    JList<Song> list;
    ArrayList<Song> songList;
    ListModel songModelList;
    private static final String FILE =  "songs.txt";
    JPanel loadPanel, addBtnPanel;
    JButton btnLoad, btnSort, btnAdd, btnSave;
    JTextField txtArtist, txtName;

    public static void main(String[] args){
        App a = new App();
    }

    public App(){
        frame = new JFrame("Playlist");

        loadPanel = createLoadPanel();
        loadPanel.setBackground(Color.BLUE);

        JPanel btnPanel = createButtonPanel();
        btnPanel.setBackground(Color.ORANGE);
        frame.getContentPane().add(btnPanel,BorderLayout.EAST);
        frame.getContentPane().add(loadPanel,BorderLayout.CENTER);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
//      frame.pack();s
        frame.setVisible(true);

    }

    public JPanel createButtonPanel(){
        JPanel panel = new JPanel();
        btnLoad = new JButton("Load List");
        btnSort = new JButton("Sort list");
        btnAdd = new JButton("Add");
        btnSort.addActionListener(new ActionListener() { //here is the action listener for the button used for sorting

            @Override
            public void actionPerformed(ActionEvent e) {
//              Collections.sort(songList);
//              songModelList.setList(songList);
                songModelList.getSortedList(songList);
                list.updateUI();
            }
        });
        btnLoad.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                loadPanel.setVisible(true);
            }
        });
        btnAdd.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                addBtnPanel = createAddPanel();
            }
        });

        panel.add(btnLoad);
        panel.add(btnSort);
        panel.add(btnAdd);

        return panel;
    }

    public JPanel createAddPanel(){
        JFrame frame = new JFrame();
        JPanel panel = new JPanel(new GridLayout(3,2));
        JLabel lblName = new JLabel("Name");
        JLabel lblArtist = new JLabel("Artist");
        txtName = new JTextField(15);
        txtArtist = new JTextField(15);
        panel.add(lblName);
        panel.add(txtName);
        panel.add(lblArtist);
        panel.add(txtArtist);
        btnSave = new JButton("Save");
        panel.add(btnSave);
        btnSave.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                String name = txtName.getText();
                String artist = txtArtist.getText();
                Song s = new Song(name, artist);
                songModelList.getSongList().add(s);
                list.updateUI();
            }
        });

        frame.getContentPane().add(BorderLayout.CENTER,panel);
        frame.setVisible(true);
        frame.setSize(new Dimension(300,100));
        return panel;
    }

    public JPanel createLoadPanel(){
        JPanel LoadPanel = new JPanel();
        list = new JList<Song>();
        songList = loadFromFile();
        songModelList = new ListModel(songList);
        songList = new ArrayList<Song>();
        list.setModel(songModelList);
        list.getSelectionModel().setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        LoadPanel.add(list);
        LoadPanel.setVisible(false);
        return LoadPanel;

    }

    public ArrayList<Song> loadFromFile(){
        ArrayList<Song> array = new ArrayList<Song>();
        try{
            BufferedReader reader = new BufferedReader(new FileReader(FILE));
            String line = null;
            while((line = reader.readLine()) != null){
                String[] parts = line.split(" - ");
                if(parts.length == 2){
                    String name = parts[0];
                    String artist = parts[1];
                    Song s = new Song(name, artist);
                    array.add(s);
                }
                else{
                    System.out.println("Invalid line!");
                }
            }
            reader.close();
        }catch(IOException e){
            System.out.println("File not found");
            e.printStackTrace();
        }
        return array;
    }
}

因此，JList 按照添加元素的顺序显示元素。但是如果用户想要对它们进行排序，我会制作一个排序按钮，当按下按钮时，JList 会按排序顺序显示元素。我该怎么做？我一遍又一遍地尝试，但它不起作用。

Answer 1

只需将方法 sort() 添加到 ListModel:

public void sort(){
    Collections.sort(songs);
    fireContentsChanged(this, 0, songs.size());
}

并修复 btnSort 操作:

btnSort.addActionListener(new ActionListener() { 
    @Override
    public void actionPerformed(ActionEvent e) {
        songModelList.sort();
    }
});