Question

所以我认为自己是一名初学程序员，但是点击一下按钮做一些简单的事情就很简单了吧？我先粘贴代码，然后问问题。

    /*
 * Created By Vili Milner
 */

import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

public class MainView extends JFrame implements ActionListener {

private long cookieBalance = 0;
private String stringBalance = Long.toString(cookieBalance);
private JLabel balance = new JLabel(stringBalance);

public MainView(){
    display();
}

public void display(){
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setVisible(true);
    setTitle("Cookie Clicker");
    setSize(300, 200);

    GridLayout gridOneTwo = new GridLayout(1, 2);
    GridLayout gridOneTen = new GridLayout(1, 10);
    GridLayout gridOneThree = new GridLayout(1, 3);

    Panel mainPanel = new Panel();
    mainPanel.setLayout(gridOneTwo);

    Panel upgradePanel = new Panel();
    upgradePanel.setLayout(new BoxLayout(upgradePanel, BoxLayout.Y_AXIS));
    JButton upgradeButtonOne = new JButton("UPGRADE 1");
    JButton upgradeButtonTwo = new JButton("UPGRADE 2");
    JButton upgradeButtonThree = new JButton("UPGRADE 3");
    JButton upgradeButtonFour = new JButton("UPGRADE 4");
    JButton upgradeButtonFive = new JButton("UPGRADE 5");
    upgradePanel.add(upgradeButtonOne);
    upgradePanel.add(upgradeButtonTwo);
    upgradePanel.add(upgradeButtonThree);
    upgradePanel.add(upgradeButtonFour);
    upgradePanel.add(upgradeButtonFive);
    mainPanel.add(upgradePanel);

    Panel displayPanel = new Panel();
    displayPanel.setLayout(new BoxLayout(displayPanel, BoxLayout.Y_AXIS));
    displayPanel.add(balance);
    mainPanel.add(displayPanel);

    Panel cookiePanel = new Panel();
    cookiePanel.setLayout(gridOneThree);
    JButton cookieButton = new JButton("COOKIE");
    cookieButton.setActionCommand("cookie");
    cookieButton.addActionListener(this);
    cookiePanel.add(cookieButton);
    JLabel emptyLabelOne = new JLabel(" ");
    JLabel emptyLabelTwo = new JLabel(" ");
    displayPanel.add(cookiePanel);
    displayPanel.add(emptyLabelOne);
    displayPanel.add(emptyLabelTwo);

    add(mainPanel);
}

@Override
public void actionPerformed(ActionEvent click) {
    String action = click.getActionCommand();

    if (action.equals("cookie")){
        cookieBalance++;
    }
}

}

继续，我可以让按钮做任何事情，除了使显示标签上升1.换句话说，按钮本身确实有效，但由于某种原因标签没有改变。我相信这是一个相当简单的错误，我似乎无法找到它。所以我的问题是：为什么一旦我增加值，标签就不会改变？

Answer 1

重复评论中所说的内容，JLabel balance未使用该值进行更新，它只是反映了cookieBalance原来的价值。您应该调用：

，而不是简单地递增变量

@Override
public void actionPerformed(ActionEvent click) {
    String action = click.getActionCommand();

    if (action.equals("cookie")){
        balance.setText(String.valueOf(++cookieBalance));
    }
}

按钮什么都没做？

1 个答案: