防止出现JComboBox弹出。通过InputVerifier

Question

鉴于以下情况：

InputVerifier.

• The

• one有一个JComboBox和一个JTextField

• ，后者有一个InputVerifier提供自己的错误消息。

textField是当前的焦点所有者，它的输入不能满足inputVerifier (在这里:在组合框上单击不到3 JComboBox，这将触发 InputVerifier )显示它的错误消息。

• 您确认了错误消息，然后就会出现组合框的弹出式，可以接受选择。

F 213

对我来说，这是一种不想要的行为，在inputVerifier满意之前，我希望不让其他组件更改它的输入。在所描述的场景中，JComboBox可以有自己的ActionListener，在出现新的选择时可以改变整个情况。

下面的代码通过应用PopupMenuListener来解决这个问题，它在验证器中检查一个布尔值，告诉它的状态，然后决定是否显示弹出窗口。

我现在想要做的是编写一个扩展的JComboBox类，实现这个功能，并接受所有类型的(扩展) InputVerifiers。但是我已经被困在这里的测试代码中了，因为我不知道如何让PopupMenuListener访问普通的“布尔”“满意”。如果只将一个InputVerifier作为参数传递，则需要稍后进行转换，这就不具有通用性。-还是有“可变”铸造？

任何想法都是受欢迎的，即使它是一种完全不同的方法来解决最初的问题。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.plaf.basic.*;
import javax.swing.plaf.metal.*;

public class DisableComboPopupByVerifier extends JFrame {
  public static final long serialVersionUID = 100L;

  JComboBox<String> cmb;

  public DisableComboPopupByVerifier() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(450, 240);
    setLocationRelativeTo(null);
    setLayout(new FlowLayout(FlowLayout.LEFT, 2, 2));

    cmb= new JComboBox<>(new String[]{"AA", "BB", "CC"});
    cmb.setPreferredSize(new Dimension(43, 20));
    MyMinLenVerifier verifier= new MyMinLenVerifier(this, 3);
    MyPopupListener popupListener= new MyPopupListener(verifier);
    cmb.addPopupMenuListener(popupListener);
    add(cmb);
    JTextField tf1= new JTextField(5);
    tf1.setInputVerifier(verifier);
    add(tf1);
    JTextField tf2= new JTextField(5);
    tf2.setInputVerifier(verifier);
    add(tf2);
    SwingUtilities.invokeLater(() -> tf1.requestFocusInWindow());
    setVisible(true);
  }


  static public void main(String args[]) {
    EventQueue.invokeLater(DisableComboPopupByVerifier::new);
  }


  class MyMinLenVerifier extends InputVerifier {
    boolean satisfied;
    int minlen;
    Component parent;

    public MyMinLenVerifier(Component parent, int minlen) {
      this.minlen= minlen;
      this.parent= parent;
    }

    public boolean verify(JComponent input) {
      String s= ((JTextField)input).getText();
      if (s.length()>=minlen) {
        satisfied= true;
      }
      else {
        satisfied= false;
        JOptionPane.showMessageDialog(parent,
                    "Enter at least "+minlen+" characters.",
                    "Error", JOptionPane.ERROR_MESSAGE);
      }
      return satisfied;
    }
  }


  class MyPopupListener implements PopupMenuListener {
//** To accept all kinds of verifiers the specific one here needs to be replaced
 by the super class InputVerifier, which, however, makes casting necessary to access the boolean 'satisfied' below.
**//
    MyMinLenVerifier verifier;

    public MyPopupListener(MyMinLenVerifier verifier) {
      this.verifier= verifier;
    }

    public void popupMenuCanceled(PopupMenuEvent e) {
    }
    public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
    }
    public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
//**  boolean 'satisfied' is a requirement in all passed verifiers. **//
      if (!verifier.satisfied) {
        BasicComboPopup popup= (BasicComboPopup)cmb.getUI()
                                        .getAccessibleChild(cmb, 0);
        SwingUtilities.invokeLater(() -> {
          popup.setVisible(false);
//        This restauration of the button background is not reliable!
          MetalComboBoxButton btn= (MetalComboBoxButton)cmb.getComponent(0);
          btn.getModel().setPressed(false);
          btn.repaint();
          ((JComboBox)e.getSource()).repaint();
        });
      }
    }
  }

}

Answer 1

由于缺乏更好的想法，我在MyMinLenVerifier中忽略了MyMinLenVerifier()

    @Override
    public String toString() {
      return "satisfied:"+satisfied;
    }

MyPopupListener类现在看起来如下所示：

  class MyPopupListener implements PopupMenuListener {
    InputVerifier verifier;

    public MyPopupListener(InputVerifier verifier) {
      this.verifier= verifier;
    }

.
.
.
    public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
      if (verifier.toString().endsWith("false")) {
...