如何在Java中再次单击按钮时执行第二个操作？

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!"); 
     } 
    }); 

这是我第一次点击它时发生的情况。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

保持一个状态变量（类字段），指示是否按钮已经被点击：

private boolean hasBeenClicked = false; 

然后改变你的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; 
    } 

这最后的操作手段如果hasBeenClicked是false，它将变成true，如果它是true它将变成false。所以如果你愿意，你可以重复一遍。

Answer 2

你可以使用你的ActionListener内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

如果这是你想要的OT实现，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

使用sentinelinstance variable内你的班级在两个动作之间切换。

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; 
     } 
    } 
});