关于下面的代码，我试图让BOOKGUI类访问BOOKSHELF类并从方法返回值。
BOOKSHELF CLASS
public int sizeOfBookshelf()
{
return books.size();
}
在BOOKGUI类
JButton button3 = new JButton("Size of BookShelf");
content.add(button3);
button3.addActionListener(this);
if (e.getActionCommand().equals("Size of BookShelf"))
return books.size();
BOOKGUI CLASS
import java.awt.FlowLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.util.ArrayList;
public class BookGUI extends JFrame implements ActionListener
{
Book book = new Book("", "", 0, "", 0);
String title = "";
String author = "";
int year = 0;
String publisher = "";
double cost = 0;
public BookShelf bookShelf = new BookShelf();
public static final int WIDTH = 300;
public static final int HEIGHT = 200;
//Creates & displays a window of the class FlowLayoutDemo
public static void main(String[] args)
{
BookGUI gui = new BookGUI( );
gui.setVisible(true);
}
public void setTitle(String title) //this is relevant
{
this.title = title;
}
public void setAuthor(String author) //this is relevant
{
this.author = author;
}
public void setYear(int year) //this is relevant
{
this.year = year;
}
public void setPublisher(String publisher) //this is relevant
{
this.publisher = publisher;
}
public void setCost(int cost) //this is relevant
{
this.cost = cost;
}
public BookGUI( )
{
setSize(WIDTH, HEIGHT);
addWindowListener(new WindowDestroyer( ));
setTitle("GUI Assignment");
Container content = getContentPane( );
content.setLayout(new FlowLayout());
JButton button1 = new JButton("Title");
content.add(button1);
button1.addActionListener(this);
//contentPane.add(button1);
JButton button2 = new JButton("Author");
content.add(button2);
button2.addActionListener(this);
JButton button3 = new JButton("Size of BookShelf");
content.add(button3);
button3.addActionListener(this);
JButton button4 = new JButton("Add Book");
content.add(button4);
button4.addActionListener(this);
}
public void actionPerformed(ActionEvent e)
{
if (e.getActionCommand().equals("Add Book"))
//book = JOptionPane.showInputDialog("Add Book");
//set up the book object with all the data passed in
title = JOptionPane.showInputDialog("Title");
author = JOptionPane.showInputDialog("Author");
publisher = JOptionPane.showInputDialog("Publisher");
book.setTitle(title);
book.setAuthor(author);
book.setPublisher(publisher);
bookShelf.addBook(book);
// set up each individual title, author, etc. use joptionpane and mutators?
//exception handling...
// add the book to the bookShelf
String message = "The title of the book is :" + title +
"the Author of the Book is : " + author + " and it's published by " + publisher;
//TAKE A LOOK AT THIS //JOptionPane.showMessageDialog(
//null, " The sum is " + sum, "Results",
//JOptionPane.PLAIN_MESSAGE );
//System.exit( 0 );
JOptionPane.showMessageDialog(null, message, "Book Details", JOptionPane.PLAIN_MESSAGE);
//Container content = getContentPane( );
if (e.getActionCommand().equals("Size of BookShelf"))
return books.size();
//return sizeofBookshelf();
//String message = "Number of books in shelf "+books.sizeOfBookshelf();
//JOptionPane.showMessageDialog(null, message, "Book Shelf", JOptionPane.PLAIN_MESSAGE);
//sizeOfBookshelf = JOptionPane.showInputDialog("Size");
//sizeOfBookshelf = Integer.valueOf(JOptionPane.showInputDialog(null, "Enter size of bookshelf"));
//label2 = new JButton("Get Book Information");
//content.add(label2);
//JButton label3 = new JButton("Show Total Cost of Books");
//content.add(label3);
}
}
BOOKSHELF CLASS
import java.util.ArrayList;
/**
* This class holds an ArrayList of Book. There are methods for adding Book objects to the ArrayList,
* calculating the total cost of all books in the ArrayList, determining how many Book objects are
* in the ArrayList and determining the highest price paid for any one Book.
*
* @version 1.0
*/
public class BookShelf
{
//create an ArrayList of Book.
public ArrayList<Book> books;
public BookShelf()
{
books = new ArrayList<Book>();
}
/**
* This method adds a Book object to the ArrayList
*
* @param theBook The book object that will be added to the ArrayList
*
*/
public void addBook(Book theBook)
{
books.add(theBook);
}
/**
* This method returns the size of the ArrayList, that is, the number of books
* that have been added to the ArrayList
*
* @return The size of the ArrayList
*/
public int sizeOfBookshelf()
{
return books.size();
}
/**
* This method calculates the cost of the book shelf, that is, it totals the
* cost of all the books in the ArrayList and returns it.
*
* @return The cost of the book shelf
*/
public double costOfBookshelf(){
double total = 0;
for(Book book : books) {
total = total + book.getCost();
}
return total;
}
//create a method called highestPricePAid that will return the cost of the most expensive book in the ArrayList
/**
* This method finds the price of the most expensive book in the ArrayList and returns it.
*
* @return The cost of the most expensive book on the book shelf
*/
public double highestPricePaid(){
double highestPrice = 0;
for(Book book : books) {
if((highestPrice == 0) || (highestPrice < book.getCost())) {
highestPrice = book.getCost(); }
}
return highestPrice;
}
}
但我在Eclipse中遇到错误。
我完全走错了路吗？
任何协助将不胜感激。感谢
答案 0 :(得分：1)
这看起来像是家庭作业，所以我给你一个提示：）
做类似
的事情e.getActionCommand()
首先需要为JButton设置一个操作命令：
buttonX.setActionCommand("do something");
有关详细信息，请参阅ActionEvent和setActionCommand()。
答案 1 :(得分：0)
如果要在sizeOfBookshelf对象上调用bookShelf方法，则语法为
bookShelf.sizeOfBookshelf()
，而不是
books.size()
此外，actionPerformed的返回类型无效。您不能从void方法返回int值。如果要显示书籍数量，请使用System.out.println(bookShelf.sizeOfBookshelf())（在控制台中记录），或使用JOptionPane将其显示在对话框中，就像您在评论代码中所做的那样：
if (e.getActionCommand().equals("Size of BookShelf")) {
int sizeOfBookShelf = bookShelf.sizeOfBookshelf();
String message = "The book shelf has " + sizeOfBookShelf + " book(s)";
JOptionPane.showMessageDialog(this, message);
}