Question

    buttonOne = new JButton("Who are you?");
    buttonOne.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            nameField.setText("Taha Sabra");
            ageField.setText("24 years old");
            buttonOne.setText("Clear Me!");
        }
    });

这是我第一次点击时发生的情况。现在，一旦按钮显示Clear Me !,我希望能够再次单击它并清除nameField和ageField。谢谢！

Answer 1

保持状态变量（类字段），指示是否已单击该按钮：

private boolean hasBeenClicked = false;

然后更改actionPerformed的逻辑：

    public void actionPerformed(ActionEvent arg0) {
        if ( ! hasBeenClicked ) {
            nameField.setText("Taha Sabra");
            ageField.setText("24 years old");
            buttonOne.setText("Clear Me!");
        } else {
            // Clear the fields
            nameField.setText("");
            ageField.setText("");

            // Set the the text on the button to the original.
            buttonOne.setText("Who are you?");
        }
        hasBeenClicked = ! hasBeenClicked;
    }

最后一项操作意味着如果hasBeenClicked为false，则会true，如果是true，则会false。{{1}}如果您愿意，可以再次重复此操作。

Answer 2

你可以在ActionListener中使用一个简单的布尔标志：

buttonOne = new JButton("Who are you?");
buttonOne.addActionListener(new ActionListener() {
    boolean clicked = false;
    @Override
    public void actionPerformed(ActionEvent e) {
        if (clicked) {
            nameField.setText("");
            ageField.setText("");
            buttonOne.setText("Clear me again!");
        } else {
            nameField.setText("Taha Sabra");
            ageField.setText("24 years old");
            buttonOne.setText("Clear Me!");
            clicked = true;
        }
    }
});

Answer 3

如果你想要的只是你想要的，你也可以使用三元运算符：

public void actionPerformed(ActionEvent arg0) {
    nameField.setText(nameField.getText().equals("") ? "Taha Sabra" : "");
    ageField.setText(ageField.getText().equals("") ? "24 years old" : "");
    buttonOne.setText(buttonOne.getText().equals("Clear Me!") ? "Who are you?" : "Clear Me!");
}

Answer 4

在班级中使用sentinel instance variable来切换这两项操作。

boolean clicked = false;

...

buttonOne = new JButton("Who are you?");
buttonOne.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if (!clicked) {
          nameField.setText("Taha Sabra");
          ageField.setText("24 years old");
          buttonOne.setText("Clear Me!");
          clicked = true;
        } else {
          nameField.setText("");
          ageField.setText("");
          clicked = false;
        }
    }
});

在Java中再次单击时，如何使按钮执行第二个操作？

4 个答案: