JFrame - ActionListener

Question

我正在构建一个使用JFrame的程序。我最终想要的结果是实现一个ActionListener，当用户单击一个按钮时它将删除标签。例如：当用户点击JButton时，5个标签中的一个从框架中移除。当他们再次点击该按钮时，其余的4个标签中的一个被删除...等等，直到剩下0个标签。从技术上讲，我有程序按要求工作，但是，我试图看看是否有方法通过循环实现ActionListener事件，而不是为每个单独的标签列出if语句。非常感谢！

import java.awt.*; 
import javax.swing.*; 
import java.awt.event.*; 

//calls for public class to inherit features of JFrame within Java 
public class NoPurchaseReason extends JFrame implements ActionListener { 

private int removeText = 0; 

JButton btn = new JButton("Select"); 

JLabel lbl = new JLabel("Found better price"); 
JLabel lbl1 = new JLabel("Not as shown on website"); 
JLabel lbl2 = new JLabel("Wrong product"); 
JLabel lbl3 = new JLabel("Damaged upon delivery"); 
JLabel lbl4 = new JLabel("None of the above"); 

public static void main(String[] args) { 
    JFrame f = new NoPurchaseReason("Please tell us why you wish to return your purchase."); 
    f.setBounds(300, 100, 500, 500); 
    f.setVisible(true); 
    f.setBackground(Color.blue); 
} 

public NoPurchaseReason(String title) { 
    super(title); 
    setLayout(null); 
    lbl.setBounds(40, 40, 600, 40); 
    btn.setBounds(320, 10, 80, 20); 
    lbl.setBounds(100, 40, 100, 20); 
    lbl1.setBounds(100, 70, 100, 20); 
    lbl2.setBounds(100, 100, 150, 20); 
    lbl3.setBounds(100, 130, 100, 20); 
    lbl4.setBounds(100, 160, 100, 20); 

    add(btn); 
    add(lbl); 
    add(lbl); 
    add(lbl1); 
    add(lbl2); 
    add(lbl3); 
    add(lbl4); 
    btn.addActionListener(this); 
} 

public void actionPerformed(ActionEvent e) { 
    removeText++; 
    if (removeText == 1) { 
     lbl.setVisible(false); 
     lbl1.setBounds(100, 40, 100, 20); 
     lbl2.setBounds(100, 70, 100, 20); 
     lbl3.setBounds(100, 100, 150, 20); 
     lbl4.setBounds(100, 130, 100, 20); 
    } 
    if (removeText == 2) { 
     lbl1.setVisible(false); 
     lbl2.setBounds(100, 40, 100, 20); 
     lbl3.setBounds(100, 70, 150, 20); 
     lbl4.setBounds(100, 100, 100, 20); 
    } 
    if (removeText == 3) { 
     lbl2.setVisible(false); 
     lbl3.setBounds(100, 40, 150, 20); 
     lbl4.setBounds(100, 70, 100, 20); 
    } 
    if (removeText == 4) { 
     lbl3.setVisible(false); 
     lbl4.setBounds(100, 40, 100, 20); 
    } 
    if (removeText == 5) { 
     lbl4.setVisible(false); 
    } 
} 

}

Answer 1

学习如何正确使用layout managers会为你节省很多的麻烦，从长远来看。

你还会发现人们会告诉你要坚持single responsibility principle，并避免犯类违反这个原则的类（例如，扩展JFrame和实现ActionListener）。

你也会听到人们告诉你比操作监听器更喜欢使用动作（如果你需要跨多个组件共享功能，那就是）。

一个简单的方法是专用整个面板来保存标签，并直接删除面板中的第一个标签，直到没有更多标签。这里有一个例子：

import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 

class LabelDemo 
{ 
    public static void main(String[] args) { 
     String[] labels = { 
       "Found better price", 
       "Not as shown on website", 
       "Wrong product", 
       "Damaged upon delivery", 
       "None of the above" 
     }; 
     final JFrame frame = new JFrame(); 
     final JPanel panel = new JPanel(); 
     panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); 
     for (String s: labels) { 
      panel.add(new JLabel(s)); 
     } 
     frame.add(panel); 
     JButton button = new JButton("Select"); 
     button.addActionListener(new ActionListener() { 
      @Override public void actionPerformed(ActionEvent e) { 
       if (panel.getComponentCount() > 0) 
        panel.remove(0); 
       frame.repaint(); 
      } 
     }); 
     frame.add(button, BorderLayout.NORTH); 
     frame.pack(); 
     frame.setVisible(true); 
    } 
} 

而且，你可能只是心里有一定的目标，我是不知道的，但说实话看起来像一个清单将是在这种情况下更好。这里有一个例子：

String[] labels = { 
     "Found better price", 
     "Not as shown on website", 
     "Wrong product", 
     "Damaged upon delivery", 
     "None of the above" 
}; 
JList<String> list = new JList<>(labels); 
int option = JOptionPane.showConfirmDialog(null, list, 
     "Please tell us why you wish to return your purchase.", 
     JOptionPane.OK_CANCEL_OPTION); 
if (option == JOptionPane.OK_OPTION) { 
    String selectedValue = list.getSelectedValue(); 
    System.out.println(selectedValue); // Do something with it. 
}