说明：
Write a WidgetViewer GUI that has the following widgets:
a button labeled "go up/down"
a label initialized to 0 (we'll call this the left label)
a label initialized to 0 (we'll call this the right label)
a button labeled "go down/up"
When the "go up/down" button is pushed, a random number between 1 and 10 (inclusive)
is generated and added to the left label, and another random number between 1 and 10 (inclusive)
is generated and subtracted from the right label.
When the "go down/up" button is pushed, a random number between 1 and 10 (inclusive) is
generated and subtracted from the left label, and another random number between 1 and 10
(inclusive) is generated and added to the right label.
错误消息：
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "Go up/down"
代码：
我似乎无法弄清楚此错误消息，它可能有可能我正在添加字符串，但我不确定，这可能是我的逻辑。但是我试图弄清楚我如何获得名为goupdown和godownup的Jbutton来显示一个随机数，然后根据需要加或减1。
public class UpAndDown {
public UpAndDown() {
WidgetViewer wv = new WidgetViewer();
JButton goUpDown = new JButton("Go up/down");
JLabel leftLabel = new JLabel("0");
wv.add(goUpDown, 10, 30, 150, 20);
wv.add(leftLabel, 10, 60, 150, 25);
JButton goDownUp = new JButton("Go down/up");
JLabel rightLabel = new JLabel("0");
wv.add(goDownUp, 10, 120, 150, 20);
wv.add(rightLabel, 10, 160, 150, 25);
ButtonIncrement action = new ButtonIncrement(goUpDown);
goUpDown.addActionListener(action);
ButtonIncrement action2 = new ButtonIncrement(goDownUp);
goDownUp.addActionListener(action2);
}
static class ButtonIncrement implements ActionListener {
private final JButton goUpDownBtn;
private final JButton goDownUpBtn;
public ButtonIncrement(JButton buttonToModify) {
goUpDownBtn = buttonToModify;
goDownUpBtn = buttonToModify;
}
@Override
public void actionPerformed(ActionEvent e) {
int rand = (int) (Math.random() * 10);
String val = goUpDownBtn.getText();
//JButton jc = (JButton) e.getSource();
int newVal = Integer.parseInt(val) + rand;
goDownUpBtn.setText(String.valueOf(newVal));
//jc.setText(goDownUpBtn.getText() + " " + val);// get string, convert to int, add rand value. then convert int back to string and set text to string
/*String val2 = goDownUpBtn.getText();
int newVal2 = Integer.parseInt(val2) + rand;
goDownUpBtn.setText(String.valueOf(newVal2));*/
}
}
编写具有以下小部件的WidgetViewer GUI：
标记为“向上/向下”的按钮，其标签初始化为0（我们称为这是左侧标签）初始化为0的标签（我们将其称为右侧标签）标为“向下/向上”的按钮]
按下“向上/向下”按钮时，将在1到1之间的一个随机数生成10（含）并添加到左侧标签，另一个生成并减去1到10（含）之间的随机数从右边的标签。
按下“向下/向上”按钮时，将在1到1之间的一个随机数生成10（含）并从左侧标签中减去，并且另一个介于1和10（含）之间的随机数会生成，并且添加到正确的标签。
所以，有很多重要的事情需要我们解决。
所以，我们可以简单地开始于
class IncrementDecrementAction implements ActionListener {
private final JLabel leftLabel;
private final JLabel rightLabel;
private int leftValue = 0;
private int rightValue = 0;
public IncrementDecrementAction(JLabel leftLabel, JLabel rightLabel) {
this.leftLabel = leftLabel;
this.rightLabel = rightLabel;
}
@Override
public void actionPerformed(ActionEvent e) {
int rand = (int) (Math.random() * 10) + 1;
leftValue += rand;
rand = (int) (Math.random() * 10) + 1;
rightValue += rand;
this.leftLabel.setText(Integer.toString(leftValue));
this.rightLabel.setText(Integer.toString(rightValue));
}
}
好的，但这只能从一个方向解决问题，向下/向上怎么办？
好吧，我们可以编写第二个ActionListener来处理这个问题，但是随后您需要某种模型来维护左右值，以便两个侦听器都知道当前值是什么。这不是一个不合理的想法，但是要使它起作用，还需要另外两个类。
相反，我们可以利用ActionEvent的actionCommand支持，并为每个按钮指定一个特定的名称，我们可以在触发操作时进行查找...
class IncrementDecrementAction implements ActionListener {
private final JLabel leftLabel;
private final JLabel rightLabel;
private int leftValue = 0;
private int rightValue = 0;
public IncrementDecrementAction(JLabel leftLabel, JLabel rightLabel) {
this.leftLabel = leftLabel;
this.rightLabel = rightLabel;
}
@Override
public void actionPerformed(ActionEvent e) {
int leftRandom = (int) (Math.random() * 10) + 1;
int rightRandom = (int) (Math.random() * 10) + 1;
if (e.getActionCommand().equals("upDown")) {
leftValue += leftRandom;
rightValue -= rightRandom;
} else if (e.getActionCommand().equals("downUp")) {
leftValue -= leftRandom;
rightValue += rightRandom;
}
this.leftLabel.setText(Integer.toString(leftValue));
this.rightLabel.setText(Integer.toString(rightValue));
}
}
这基本上是根据事件的来源改变了计算的方向，并且无需现在就知道事件的实际来源是什么（按钮，菜单项，键绑定），它只是做了不在乎。
例如，您只需将适当的actionCommand应用于适当的Jbutton即可进行设置...
public class TestPane extends JPanel {
private JLabel leftLabel;
private JLabel rightLabel;
private JButton upDownButton;
private JButton downUpButton;
public TestPane() {
leftLabel = new JLabel("0");
rightLabel = new JLabel("0");
upDownButton = new JButton("Up/down");
downUpButton = new JButton("Down/up");
upDownButton.setActionCommand("upDown");
downUpButton.setActionCommand("downUp");
ActionListener actionListener = new IncrementDecrementAction(leftLabel, rightLabel);
upDownButton.addActionListener(actionListener);
downUpButton.addActionListener(actionListener);
add(leftLabel);
add(rightLabel);
add(upDownButton);
add(downUpButton);
}
}
现在，在理解这一点之前，我经历了十几个想法-我的观点是尝试使它尽可能简单，而又不尝试引入可能不需要添加的一堆复杂性-提防-我不知道练习的目的是什么，所以我可能已经从您的老师试图让您做的那一个方向走错了]