允许"Enter"键按下提交按钮,而不是仅使用MouseClick

Question

我现在正在学习Swing课程以及它的一切.我已经把这个玩具程序放在一起,提示输入一个名字然后出现一个JOptionPane,上面写着"你输入了(你的名字)".我只能点击我使用的提交按钮,但我也想让它与Enter按钮一起使用.我已经尝试添加KeyListener,正如我正在使用的Java书中推荐的那样(Eventful Java,Bruce Danyluk和Murtagh).

这是我的代码:

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class NamePrompt extends JFrame{


    private static final long serialVersionUID = 1L;

    String name;

    public NamePrompt(){

        setLayout(new BorderLayout());

        JLabel enterYourName = new JLabel("Enter Your Name Here:");
        JTextField textBoxToEnterName = new JTextField(21);
        JPanel panelTop = new JPanel();
        panelTop.add(enterYourName);
        panelTop.add(textBoxToEnterName);

        JButton submit = new JButton("Submit");
        submit.addActionListener(new SubmitButton(textBoxToEnterName));
        submit.addKeyListener(new SubmitButton(textBoxToEnterName));
        JPanel panelBottom = new JPanel();
        panelBottom.add(submit);

        //Add panelTop to JFrame
        add(panelTop, BorderLayout.NORTH);
        add(panelBottom, BorderLayout.SOUTH);

        //JFrame set-up
        setTitle("Name Prompt Program");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);


    }



    public static void main(String[] args) {
        NamePrompt promptForName = new NamePrompt();
        promptForName.setVisible(true); 
    }


}

这是actionListener,keyListener类:

import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextField;


public class SubmitButton implements ActionListener, KeyListener {

    JTextField nameInput;


    public SubmitButton(JTextField textfield){
        nameInput = textfield;
    }

    @Override
    public void actionPerformed(ActionEvent submitClicked) {

        Component frame = new JFrame();
        JOptionPane.showMessageDialog(frame , "You've Submitted the name " + nameInput.getText());
    }

    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode()==KeyEvent.VK_ENTER){
            System.out.println("Hello");
        }
        Component frame = new JFrame();
        JOptionPane.showMessageDialog(frame , "You've Submitted the name " + nameInput.getText());

    }

    @Override
    public void keyReleased(KeyEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void keyTyped(KeyEvent arg0) {

    }
}

Answer 1

有一个简单的技巧.用所有按钮构造框架后,执行以下操作:

frame.getRootPane().setDefaultButton(submitButton);

对于每个帧,您可以设置一个默认按钮,该按钮将自动侦听Enter键(可能还有其他一些我不知道的事件).当您在该帧中按Enter键时,actionPerformed()将调用ActionListeners的方法.

就我所看到的,你的代码问题在于,每次敲击键时都会弹出对话框,因为你没有把它放在if-body中.尝试将其更改为:

@Override
public void keyPressed(KeyEvent e) {
    if (e.getKeyCode()==KeyEvent.VK_ENTER){
        System.out.println("Hello");

        JOptionPane.showMessageDialog(null , "You've Submitted the name " + nameInput.getText());
    }

}

更新:我发现你的代码有什么问题.您正在将键侦听器添加到"提交"按钮而不是TextField.将您的代码更改为:

SubmitButton listener = new SubmitButton(textBoxToEnterName);
textBoxToEnterName.addActionListener(listener);
submit.addKeyListener(listener);

Answer 2

您可以使用顶级容器根窗格来设置默认按钮,这将允许它响应回车.

SwingUtilities.getRootPane(submitButton).setDefaultButton(submitButton);

当然,这假设您已将按钮添加到有效容器中;)

更新

这是使用JRootPane#setDefaultButton和键绑定API 的基本示例

public class DefaultButton {

    public static void main(String[] args) {
        new DefaultButton();
    }

    public DefaultButton() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public class TestPane extends JPanel {

        private JButton button;
        private JLabel label;
        private int count;

        public TestPane() {

            label = new JLabel("Press the button");
            button = new JButton("Press me");

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridy = 0;
            add(label, gbc);
            gbc.gridy++;
            add(button, gbc);
            gbc.gridy++;
            add(new JButton("No Action Here"), gbc);

            button.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    doButtonPressed(e);
                }

            });

            InputMap im = button.getInputMap(WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
            ActionMap am = button.getActionMap();

            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), "spaced");
            am.put("spaced", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    doButtonPressed(e);
                }

            });

        }

        @Override
        public void addNotify() {
            super.addNotify();
            SwingUtilities.getRootPane(button).setDefaultButton(button);
        }

        protected void doButtonPressed(ActionEvent evt) {
            count++;
            label.setText("Pressed " + count + " times");
        }

    }

}

当然,这假设具有焦点的组件不消耗有问题的键事件(例如消耗space或enter键的第二个按钮)