[英]Adding to a JList with an ActionListener and refresihing GUI frame after adding
我正在使用Java的一些GUI組件進行一個項目(是的,這是在學校里,不,我不想讓任何人為我編寫它。我感到非常自豪!)。 它仍處於相當艱難的階段,並且有一件事情使我無法完成任務。 除非我確實需要幫助,否則我盡量不要尋求幫助,因為通常當我確實提出請求時,結果證明這是一個簡單的錯誤,因此,在這種情況下,請放輕松。 無論如何,依此類推。 這是一個小組項目,因此我對我的伴侶的一些評論。 我會問他們,但現在是凌晨4點...無論如何,這是。 不知道為什么在所有這些單獨的框中。 我所困擾的監聽器是ActionPerformed,在底部附近。 在此先感謝您的幫助。
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class GUI extends JFrame
{
private JPanel panel;
private JFrame frame;
private JTextArea text;
private MP3List list = new MP3List();
private JList songList;
private JScrollPane scrollList;
private JMenuBar menuBar;
private JMenu menu;
private JMenuItem menuAdd;
private String[] songs;
private static String mp3msg = "Project 2: MP3 Tracker"; // Header for JOptionPane
public GUI()
{
super("mp3");
panel = new JPanel();
createGUI();
add(panel);
}
public void createGUI()
{
//This creates the frame(createGUI)
frame = new JFrame();
//Here, I made an array of the song titles and gave them to a JList
//for display. Do you think we should sort the songs?
songs = new String[list.getSize()];
for (int i = 0; i < list.getSize(); i++)
{
songs[i] = list.get(i).getSongTitle();
}
songList = new JList(songs);
//Set the selection mode to single as I want to fill in fields with info on a clicked song. More on
//that to come.
songList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
//Made a scroll bar(vertical and horizontal just in case)
scrollList = new JScrollPane(songList, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
text = new JTextArea(30, 30);
text.setText("This section will hold information about songs and somesuch.");
menuBar = new JMenuBar();
menu = new JMenu("File");
menuAdd = new JMenuItem("Add Song");
menuAdd.addActionListener(new menuListener());
menu.add(menuAdd);
menuBar.add(menu);
frame.setLayout(new Border());
songList.addListSelectionListener(new ListSelectionListener()
{
public void valueChanged(ListSelectionEvent e)
{
int selectedVar;
selectedVar = songList.getSelectedIndex();
text.setText(("Song Title: " + list.get(selectedVar).getSongTitle())
+ ("\nArtist: " + list.get(selectedVar).getArtistName())
+ ("\nPlayback Time: " + list.get(selectedVar).getPlayBackTime())
+ (" || Cost: " + list.get(selectedVar).getDownloadCost())
+ (" || Size: " + list.get(selectedVar).getFileSize()));
}
});
}
public class Border extends JFrame implements LayoutManager
{
private static final long serialVersionUID = 1L;
private final int WINDOW_WIDTH = 400;
private final int WINDOW_HEIGHT = 300;
public Border()
{
super("MP3 Editor");
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
add(scrollList, BorderLayout.CENTER);
add(text, BorderLayout.SOUTH);
setJMenuBar(menuBar);
setVisible(true);
}
@Override
public void addLayoutComponent(String name, Component comp)
{
// TODO Auto-generated method stub
}
@Override
public void layoutContainer(Container parent)
{
// TODO Auto-generated method stub
}
@Override
public Dimension minimumLayoutSize(Container parent)
{
// TODO Auto-generated method stub
return null;
}
@Override
public Dimension preferredLayoutSize(Container parent)
{
// TODO Auto-generated method stub
return null;
}
@Override
public void removeLayoutComponent(Component comp)
{
// TODO Auto-generated method stub
}
}
public class menuListener extends JMenuItem implements ActionListener
{
/**
*
*/
private static final long serialVersionUID = 1L;
/*public menuListener()
{
menuItem.addActionListener(this);
}*/
public void actionPerformed(ActionEvent e)
{
MP3 aSong = getInfo();
list.add(aSong);
songs = new String[list.getSize()];
for (int i = 0; i < list.getSize(); i++)
{
songs[i] = list.get(i).getSongTitle();
}
songList = new JList(songs);
scrollList = new JScrollPane(songList, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
int index = 0;
songList.setSelectedIndex(index);
songList.ensureIndexIsVisible(index);
}
}
/**
* Input one set of MP3 file information and produce a report <br>
* <p/>
* <hr>
* Date created: Sep 22, 2010 <br>
* Date last modified: Sep 22, 2010 <br>
* <p/>
* <hr>
*/
public static MP3 getInfo()
{
// Gather all information using JOptionPane
String title = JOptionPane.showInputDialog(null,
"Enter Title: ",
mp3msg,
JOptionPane.QUESTION_MESSAGE);
String artist = JOptionPane.showInputDialog(null,
"Enter Artist: ",
mp3msg,
JOptionPane.QUESTION_MESSAGE);
int seconds = Integer.parseInt(JOptionPane.showInputDialog(null,
"Enter playback time in seconds: ",
mp3msg,
JOptionPane.QUESTION_MESSAGE));
double cost = Double.parseDouble(JOptionPane.showInputDialog(null,
"Enter download cost: ",
mp3msg,
JOptionPane.QUESTION_MESSAGE));
double size = Double.parseDouble(JOptionPane.showInputDialog(null,
"Enter file size in megabytes (MB): ",
mp3msg,
JOptionPane.QUESTION_MESSAGE));
MP3 asong = new MP3(title, artist, seconds, cost, size);
return asong;
}
}
您的代碼有很多小問題,但是我認為對您來說最重要的是在動作偵聽器中添加新MP3的部分(您說需要幫助的部分)。 在這里,您將創建一個全新的JList
並覆蓋以前的JList
,並為其創建一個新的滾動窗格,但是您沒有將新的JList添加到您的GUI中,因此舊的JList仍然存在(因此您永遠不會看到任何更改) )。
理想情況下,您應該始終保留相同的列表,並僅更新內容。 有幾種方法可以做到這一點,但是最簡單的方法之一就是簡單地調用songList.setListData(songs)
。 或者,而不是創建字符串數組,而是創建一個Vector
因為JLists也可以與Vectors一起使用。
您可能要查看的其他問題:
private JFrame frame;
從未使用過。 Border
類是一個JFrame
但也用作LayoutManager
,這非常令人困惑和錯誤。 您應該擺脫它。 就個人而言,我建議您從頭開始重寫GUI。 這是一個具有可用的JList的簡單示例,供您檢查:
package examples;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.util.Vector;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
public class GUI extends JFrame {
private final Vector<String> myVector = new Vector<String>();
private final JList myList = new JList();
public static void main(String... args) {
new GUI().setVisible(true);
}
public GUI() {
super("List");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());
add(new JButton(new AddItemAction()), BorderLayout.NORTH);
add(new JScrollPane(myList), BorderLayout.CENTER);
pack();
}
private class AddItemAction extends AbstractAction {
public AddItemAction() {
super("Add Item");
}
@Override
public void actionPerformed(ActionEvent e) {
String newItem = JOptionPane.showInputDialog("Add a new item:");
if (newItem != null) {
myVector.add(newItem);
myList.setListData(myVector);
}
}
}
}
閱讀JList API,並在Swing教程“如何使用列表”中找到第二部分的鏈接,該教程提供了一個工作示例,即在單擊按鈕時向JList添加值。 將您的代碼與工作代碼進行比較,以了解兩者之間的區別。
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