Question

 import java.awt.*;
 import java.awt.event.*;
 import javax.swing.*;

 public class TestSwingListeners1 {

    private static int cnt1;
    private static int cnt2;
    public static void main(String[] args) {
    JFrame fr1 = new JFrame("Swing Window");
    Container cp;
    JButton bt1;
    JButton bt2;
    cnt1 = 0;
    cnt2 = 0;
    String scr = null;
    String wnr = null;
    JButton btOK, btCancel;
    fr1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    fr1.setSize(300, 200);
    fr1.setResizable(false);
    cp = fr1.getContentPane();
    cp.setLayout(new GridLayout(5,1));
    btOK = new JButton("AC Milan");
    btCancel = new JButton("Real Madrid");
    JLabel lbl1 = new JLabel("Result: " + cnt1 + "X" + cnt2);
    JLabel lbl2 = new JLabel("Last Scorer: " + scr);
    JLabel lbl3 = new JLabel("Winner: " + wnr);
    cp.add(btOK);
    cp.add(btCancel);
    cp.add(lbl1);
    cp.add(lbl2);
    cp.add(lbl3);
    //lbl1.setText(displayText);

    btOK.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent ae) {
        //String displayText = "" + 1;
        cnt1++;     
        }
    });

    btCancel.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent ae) {
        cnt2++;
        }
    });
    fr1.show(); 
}

当我按下btOK按钮时，我希望cnt1递增并与btCancel相同 - 按下cnt2时增加{{1}}。

怎么做？

Answer 1

您需要使用.setText()更新标签，如：

btOK.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent ae) {
        cnt1++;
        lbl1.setText("Result: " + cnt1 + " X " + cnt2);
    }
}

你需要改变：

JLabel lbl1 = new JLabel("Result: " + cnt1 + "X" + cnt2);

到

final JLabel lbl1 = new JLabel("Result: " + cnt1 + "X" + cnt2);

因此可以从作为内部类的ActionListener访问它。

Answer 2

您需要注册ActionListener Read More

Answer 3

public class TestSwingListeners1 implements ActionListener
{

    // ...

    btOK = new JButton("AC Milan");
    btOK.setActionCommand("OK");
    btOKaddActionListener(this);

    btCancel = new JButton("Real Madrid");
    btCancel.setActionCommand("Cancel");
    btCancel.addActionListener(this);

    // ...

    public void actionPerformed(ActionEvent e)
    {
        if(e.getActionCommand().equals("OK"))
        {
            lbl1.setText("Result: " + ++cnt1 + "X" + cnt2);
        }
        else if(e.getActionCommand().equals("Cancel"))
        {
            lbl1.setText("Result: " + cnt1 + "X" + ++cnt2);
        }
    }
}

更新标签内的变量

3 个答案: