如何在Java中再次單擊按鈕時執行第二個操作？

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!"); 
     } 
    }); 

這是我第一次點擊它時發生的情況。現在，一旦按鈕顯示Clear Me！，我希望能夠再次單擊它並清除nameField和ageField。謝謝！

Answer 1

保持一個狀態變量（類字段），指示是否按鈕已經被點擊：

private boolean hasBeenClicked = false; 

然後改變你的actionPerformed的邏輯：

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; 
    } 

這最後的操作手段如果hasBeenClicked是false，它將變成true，如果它是true它將變成false。所以如果你願意，你可以重複一遍。

Answer 2

你可以使用你的ActionListener內一個簡單的布爾標誌：

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

如果這是你想要的OT實現，你也可以使用三元運算符：

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內你的班級在兩個動作之間切換。

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; 
     } 
    } 
});