我在这段代码中获得了NPE。我试图初始化每个索引,但似乎也没有工作。你能指出什么是错的吗?谢谢!
package com.js.teachEnglish;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.FileReader;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
public class Piggy_Panel extends JPanel {
/**
*
*/
private static final long serialVersionUID = 1L;
int number_lines = getLines(Helper.piggybackResource.getPath());
protected JLabel title_Label = new JLabel("Piggyback words");
protected ImageIcon button_image = new ImageIcon(Helper.soundIconResource);
protected JButton title_Button = new JButton(button_image);
protected JPanel titlePanel = new JPanel();
protected JScrollPane pane = new JScrollPane(this);
protected JLabel[] label_group = new JLabel[number_lines];
protected JButton[] button_group = new JButton[number_lines];
protected String[] information = new String[number_lines];
// Table information
protected String[] col_titles = new String[] {"",""};
protected Object[][] table_contents = new Object[number_lines][];
protected JTable table;
// constructor
public Piggy_Panel() {
setLayout(new GridLayout(number_lines+1,1));
// scroll pane
pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
pane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
// getting the information
readInformation();
/*
* adding the title seperately
* and also adding characteristics for the label
* */
titlePanel = new JPanel();
titlePanel.setLayout(new FlowLayout());
// adding the characteristics for the label
title_Label.setFont(new Font("Arial",Font.PLAIN,36));
titlePanel.add(title_Label);
titlePanel.add(title_Button);
add(titlePanel);
// calling the ini_labels_buttons() to initlialise the buttons and labels
ini_labels_buttons();
// fill the object[][] in
fill_table();
// initialising table and adding specific characteristics
table = new JTable(table_contents, col_titles);
table.setFillsViewportHeight(true);
table.setShowHorizontalLines(false);
table.setShowVerticalLines(false);
add(table);
// calling the ini_panel_group() to add everything
title_Button.addActionListener(new buttonListener());
}
// will read the information from the file
public String[] readInformation() {
try {
String line = null;
BufferedReader br = new BufferedReader(new FileReader(Helper.piggybackResource.getPath()));
int i = 0;
while((line = br.readLine()) != null) {
information[i] = line;
i++;
}
return information;
}catch(Exception ex) {
ex.printStackTrace();
}
return null;
}
// will put out the sound
// This will output the sound if a button is clicked
class buttonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JButton button = (JButton) e.getSource();
String sayDynamicPath = Helper.sayDynamicResource.getPath() + " ";
if(button.equals(title_Button)) {
try {
Runtime.getRuntime().exec(sayDynamicPath +
title_Label.getText());
}catch(Exception ex) {
JOptionPane.showMessageDialog(null,""+ex,"Unable to produce sound",
JOptionPane.ERROR_MESSAGE);
ex.printStackTrace();
}
}
}
}
// Initialising the JLabels and JButtons and also adding the relevant functions
// these include icons and information
public void ini_labels_buttons() {
// initialising the buttons first
for (int i = 0; i < button_group.length; i++) {
button_group[i] = new JButton(button_image);
}
// initialising the labels
for (int i = 0; i < label_group.length; i++) {
label_group[i] = new JLabel(information[i]);
}
}
public void fill_table() {
// fill in the first col
for (int i = 0; i < table_contents.length; i++) {
table_contents[i][0] = information[i]; // null pointer here
}
// fill in the second the col
for(int j = 0;j < table_contents.length;j++) {
table_contents[j][1] = button_group[j];
}
}
// this method will get the number of lines and then send it back
// to the label group
public int getLines(String path) {
int n = 0;
try {
BufferedReader br = new BufferedReader(new FileReader(path));
@SuppressWarnings("unused")
String line = "";
while((line = br.readLine()) != null) {
n++;
}
}catch(Exception e) {
e.printStackTrace();
}
return n;
}
}
答案 0 :(得分:2)
借用NPE的堆栈跟踪会很有用。 ;)
这会创建一个对数组的引用数组,而不是数组数组。
protected Object[][] table_contents = new Object[number_lines][];
这意味着
table_contents[i][0] = information[i];
应该抛出一个NPE,因为table_contents [i]将是null
。查看调试器将确认这一点。
最简单的解决方案是使用
创建一个或多个数组protected Object[][] table_contents = new Object[number_lines][2];
BTW我会使用一个循环而不是两个。