所以我使用链表创建了这个队列,一个 Job 对象进入队列。我仅使用这两个类文件就可以使程序运行,但现在我正在尝试使其与 GUI 一起运行。
我希望能够使用队列和作业文件从 GUI 主方法运行我的程序。我创建的 GUI 有 8 个按钮和一个用于输出的 JTextArea。我希望能够通过单击按钮来执行每个功能(入队、显示队列长度等)。
我的查询在最后
PS。为了简洁起见,原来的 main 方法被省略了。这是我要进入队列的 Job 对象,这里是一般内容...省略了 getters/setters:
public class Job
{
String ID; //(A unique number to identify each print job)
String userID; //(The login of the user that sent the document to print)
String documentName; //(The name of the document being printed)
int fileSize; //(Size of the document being printed in Kb’s)
public Job(String p, String u, String e, int f)
{ //local variables n,t,e only used in this method
printID = p;
userID = u;
documentName = e;
fileSize = f;
}
这是带有构造函数和方法的 Queue 类...据我所知,这些都可以工作。
public class Queue<Item> implements Iterable<Item>
{
private int N; // number of elements on queue
private Node first; // beginning of queue
private Node last; // end of queue
// helper linked list class
private class Node
{
private Item item;
private Node next;
}
/**
* Initialises an empty queue.
*/
public Queue()
{
first = null;
last = null;
N = 0;
// assert check();
}
//is the list empty?
public boolean isEmpty()
{
return first == null;
}
//gives number of elements in the queue
public int length()
{
return N;
}
//looks at first item, if it is empty then return error. If it has something then return
the content of the element.
public Item peek()
{
if (isEmpty()) throw new NoSuchElementException("Nothing in queue");
return first.item;
}
//add an item
public void enqueue(Item item)
{
Node oldlast = last; //move the current last to a placeholder
last = new Node(); //create a new node inside of last
last.item = item; //place the item i passed to the method call to the new last's item area
last.next = null; //set the end of the queue
if (isEmpty()) //checks the rest of the queue
first = last; //if empty creates a queue of 1 element length
else
oldlast.next = last; //if not empty then previous last will point to this new one
N++; //increment the number of elements being tracked.
}
//remove an item
public Item dequeue()
{
if (isEmpty()) throw new NoSuchElementException("Nothing in queue");
Item item = first.item;
first = first.next;
N--;
if (isEmpty()) last = null; // to avoid loitering
return item;
}
这是我的图形用户界面:
public class GUI {
public static void main(String[] args)
{
Queue s = new Queue();
JFrame frame = new JFrame("test");
frame.setVisible(true);
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel(new GridBagLayout());
frame.getContentPane().add(panel, BorderLayout.NORTH);
GridBagConstraints c = new GridBagConstraints();
JButton button1 = new JButton("Enqueue a print job");
c.gridx = 0;
c.gridy = 0;
c.insets = new Insets(10,10,10,10);
panel.add(button1, c);
button1.addActionListener(new Enqueue(){});
JButton button2 = new JButton("Dequeue a print job");
c.gridx = 0;
c.gridy = 1;
panel.add(button2, c);
button2.addActionListener(new Dequeue(){});
JButton button3 = new JButton("is the queue empty?");
c.gridx = 1;
c.gridy = 0;
panel.add(button3, c);
button3.addActionListener(new empty(){});
JButton button4 = new JButton("Print first in queue");
c.gridx = 1;
c.gridy = 1;
panel.add(button4, c);
button4.addActionListener(new first(){});
JButton button5 = new JButton("Length of queue");
c.gridx = 0;
c.gridy = 2;
panel.add(button5, c);
button5.addActionListener(new length(){});
JButton button6 = new JButton("Print entire queue");
c.gridx = 1;
c.gridy = 2;
panel.add(button6, c);
button6.addActionListener(new printAll() {});
JTextArea jTextArea = new JTextArea();
c.gridx = 4;
c.gridy = 4;
frame.add( jTextArea, BorderLayout.SOUTH);
这是有问题的内部类(在 GUI 文件中):我在这里做错了什么?我尝试过引用 's' 队列,但对于这个单独的类,队列不存在于主队列之外;这意味着我无法对其执行功能。
static class length implements ActionListener
{
public void actionPerformed (ActionEvent e)
{
System.out.println("The length of the queue is: " + s.length() +"\n");
}
}
当我知道如何处理这个 Action 监听器时,我会制作更多的 Action 监听器。
诗。如果您知道如何从我在 GUI 文件的 main 方法中创建的 actionListener 写入 JTextArea,而不是使用 Sys out,那也会对我有帮助!
这是我第一次尝试使用 GUI,所以任何见解都会很棒。谢谢:)
最佳答案
您声明:
PrintQueue s = new PrintQueue();
在 main()
方法内 - 这意味着它只能在 main()
内部(方法作用域)使用。
如果您想在方法之外使用它,则必须将其声明为类成员并通过“get()”方法公开它。
例如:
public class GUI {
static PrintQueue s = null;
public static void main(String[] args) {
s = new PrintQueue();
...
}
public PrintQueue getS() {return s;}
然后您就可以使用它了:
public void actionPerformed (ActionEvent e) {
System.out.println("The length of the queue is: " + s.length() +"\n"); //from the same class
}
或者从类外使用:
GUI gui = new Gui();
PrintQueue s = gui.getS();
评论:
我不确定 main()
是否是实例化 PrintQueue
的正确位置 - 可能是所以,但构造函数也可能是一个更好的主意。
关于java - 在另一个类中使用内部类actionListener,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/27093249/