java - 如何在文本字段中包含 'some' 文本时禁用按钮，并在该文本在文本字段中消失时重新启用它们

Question

情况是JButton1对应JLabel1，JButton2对应JLabel2，依此类推。不过，我想当 Jlabel 的值在 TextField 上返回时禁用 JButton#，并在它消失时重新启用它们。

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

public class qwerty {

ArrayList<JTextField> tfs = new ArrayList<JTextField>();
ArrayList<JButton> bts = new ArrayList<JButton>();


int counter = 0;
String answer;
JLabel j1 = new JLabel("Mark");
JLabel j2 = new JLabel("Joe");
JLabel j3 = new JLabel("John");
JLabel j4 = new JLabel("Ray");

public static void main(String[] args) {
   EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            new qwerty();
        }
    });
}
 public qwerty() {

    JFrame frame = new JFrame();
    frame.getContentPane().setLayout(new FlowLayout());

    // Add new buttons to bts
    bts.add(new JButton("Button1"));
    bts.add(new JButton("Button2"));
    bts.add(new JButton("Button3"));
    bts.add(new JButton("Button4"));

   // Add new textfields to tfs
   tfs.add(new JTextField());
   tfs.add(new JTextField());
   tfs.add(new JTextField());



   j1.setPreferredSize(new Dimension(100, 25));
   j2.setPreferredSize(new Dimension(100, 25));
   j3.setPreferredSize(new Dimension(100, 25));
   j4.setPreferredSize(new Dimension(100, 25));


    for (JButton b : bts) {
        b.addActionListener(new ButtonActionListener());
        b.setPreferredSize(new Dimension(100, 25));
        frame.getContentPane().add(b);
    }

        frame.getContentPane().add(j1);
        frame.getContentPane().add(j2);
        frame.getContentPane().add(j3);
        frame.getContentPane().add(j4);



    for (JTextField tf : tfs) {
        tf.setPreferredSize(new Dimension(100, 25));
        tf.setEditable(false);
        frame.getContentPane().add(tf);
    }


    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(500, 500);
    frame.setVisible(true);

}

public class ButtonActionListener implements ActionListener {


    @Override
    public void actionPerformed(ActionEvent e) {
        if (counter >= tfs.size()) {
            counter = 0;
        }

        String a = ((AbstractButton) e.getSource()).getText();
        if (a == "Button1"){
        tfs.get(counter).setText(j1.getText());
        }   

        if (a == "Button2"){
        tfs.get(counter).setText(j2.getText());
        }

        if (a == "Button3"){
        tfs.get(counter).setText(j3.getText());
        } 

        if (a == "Button4"){
        tfs.get(counter).setText(j4.getText());
        } 

        counter++;
    }


}

}

Answer 1

您可以使用 DocumentListener 来监视文本字段中的更改，然后设置按钮的状态。

下面是一些代码，允许您将 1 个(或更多)文本字段与按钮关联。

import java.awt.*;
import java.awt.event.*;
import java.util.List;
import java.util.ArrayList;
import javax.swing.*;
import javax.swing.event.*;

public class DataEntered implements DocumentListener
{
    private JButton button;
    private List<JTextField> textFields = new ArrayList<JTextField>();

    public DataEntered(JButton button)
    {
        this.button = button;
    }

    public void addTextField(JTextField textField)
    {
        textFields.add( textField );
        textField.getDocument().addDocumentListener( this );
    }

    public boolean isDataEntered()
    {
        for (JTextField textField : textFields)
        {
            if (textField.getText().trim().length() == 0)
                return false;
        }

        return true;
    }

    @Override
    public void insertUpdate(DocumentEvent e)
    {
        checkData();
    }

    @Override
    public void removeUpdate(DocumentEvent e)
    {
        checkData();
    }

    @Override
    public void changedUpdate(DocumentEvent e) {}

    private void checkData()
    {
        button.setEnabled( isDataEntered() );
    }

    private static void createAndShowUI()
    {
        JButton submit = new JButton( "Submit" );
        submit.setEnabled( false );

        JTextField textField1 = new JTextField(10);
        JTextField textField2 = new JTextField(10);

        DataEntered de = new DataEntered( submit );
        de.addTextField( textField1 );
        de.addTextField( textField2 );

        JFrame frame = new JFrame("SSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(textField1, BorderLayout.WEST);
        frame.add(textField2, BorderLayout.EAST);
        frame.add(submit, BorderLayout.SOUTH);
        frame.pack();
        frame.setLocationByPlatform( true );
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowUI();
            }
        });
    }
}

必须在所有文本字段中输入文本才能启用该按钮。

在您的情况下，您有文本字段到按钮的一对一映射，因此您只需在一个文本字段中输入文本即可启用相关按钮。