Java 按钮功能

Question

这是我第一次设计 GUI，我相信这可能是一个简单的问题。我试图让程序在使用System.exit(0) 按下取消按钮时关闭，但我不确定将它放在我的代码中的哪个位置。我必须创建一个单独的方法吗？我可以在我的ActionPreformed 方法中实现它吗？

//importing required packages
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.*;

//implements ActionListener
public class primecalc implements ActionListener{

    public static void main(String[] args) throws Exception {

        //create object instance
        primecalc p= new primecalc();
    }

    private JTextField Calculate,Value;
    private JButton calculateb,cancelb;
    private JLabel l1,l2;
    private JFrame frame;

    public primecalc()
    {
        //Desiging GUI
        Calculate = new JTextField(30);
        Value = new JTextField(30);
        l1 = new JLabel("Prime Number Calculator");
        calculateb = new JButton("Calculate");
        calculateb.addActionListener(this);//button performs specific action
        cancelb = new JButton("Cancel");
        cancelb.addActionListener(this);//button performs specific action

        //layout
        JPanel north = new JPanel(new GridLayout(3,2));
        north.add(new JLabel("Enter a number: "));
        north.add(Calculate);
        north.add(new JLabel("Result: "));
        north.add(Value);
        north.add(calculateb);
        north.add(cancelb);

        //frame
        JFrame frame = new JFrame("Prime Number Calculator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());
        frame.add(north,BorderLayout.NORTH);
        frame.pack();
        frame.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent event)//buttons action is performed here
    { 
        String input =Calculate.getText();
        int n1;
        boolean Prime;
        try{
            n1=Integer.parseInt(input);
            Prime=true;
            for(int i=2;i<n1;i++){
                if((n1 % i) == 0){
                    Prime=false;
                    break;
                }
            }
            if(n1==1 || n1==0){
                Prime=false;  
            }
            if(Prime){
                Value.setText("This is a prime number.");              
            }else{
                Value.setText("This is not a prime number.");              
            }
        }catch(NumberFormatException nfe){
            Value.setText("The input is invalid, please try again.");
        }
    }
}

Answer 1

你需要检查事件的来源，然后决定做什么。

@Override
public void actionPerformed(ActionEvent event) {
    if (event.getSource() == cancelb) {
        System.exit(0);
    }
    // you continue your code from here

使用这种方法，您只需要测试哪个按钮启动了事件。

Answer 2

cancelb.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
          doSomething()....
          System.Exit(0);
        }
      });

Answer 3

这样做，

@Override
    public void actionPerformed(ActionEvent e) {
        if(e.getActionCommand().equals("Cancel")){
                System.exit(0);
        }   

    }

Answer 4

为每个按钮使用不同的匿名 ActionListener

        // Designing GUI
        calculate = new JTextField(30);
        value     = new JTextField(30);

        l1 = new JLabel("Prime Number Calculator");     

        ActionListener calculatebListener = new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                     // Paste your code here
                }
        };

        calculateb = new JButton("Calculate");
        calculateb.addActionListener(calculatebListener);


        ActionListener cancelbListener = new ActionListener() {

             @Override
             public void actionPerformed(ActionEvent e) {
                   System.exit(0);
              }
        };

        cancelb = new JButton("Cancel");
        cancelb.addActionListener(cancelbListener);
        ...

Answer 5

为了您的目的，我建议您只需在按钮上添加 MouseListener 或 MouseAdapter

myButton.addMouseListener(new MouseAdapter() {
     @Override
     public void mousePressed(MouseEvent e) {
        System.exit(0);
     }
  });