使用Tab键将焦点放在按钮上，然后按Enter

Question

I have a simple jFrame with a submit button and a cancel button. Currently, everything works perfectly. User perform action on mouse click. Now I want to press 'tab' first to focus the button then it should fire whenever someone presses the enter key. It should work for both keys. What am I missing here? I am using netbean IDE. Below is a sample of the code that works perfectly using mouse click.

 private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
         String ws = null;
         if(unitno.getText().length() == 14)
        {
            String substr=unitno.getText().substring(unitno.getText().length()-4);
            if (substr.equals("0678"))
            {
                model.setSelectedItem("Tesla");
            }
            else if(substr.equals("0675"))
            {
                 model.setSelectedItem("Weber Base");
            }
            else if(substr.equals("0676"))
            {
                 model.setSelectedItem("Weber Mid");
            }
               else if(substr.equals("0677")|| substr.equals("067j")|| substr.equals("067J"))
            {
                 model.setSelectedItem("Weber PDL");
            }
        }
        try{
             Double wd = Double.parseDouble(w.getText());
             if(wd<251.43 || wd>253.03){
                  w.setForeground(Color.BLUE);
                  w.setBackground(Color.YELLOW);
                  wt.setForeground(Color.red);
             }
             else{
                   ws = w.getText();
                  w.setForeground(Color.BLACK);
                  w.setBackground(Color.WHITE);
             }

             if(ws ==null || unitno.getText().equals("")){
                int dialogButton = JOptionPane.YES_NO_OPTION;
                int dialogResult = JOptionPane.showConfirmDialog(this, "Empty field or out of spec is detected. Press YES to save and NO to edit.", "Error", dialogButton);
                if(dialogResult ==0){
                    ws = w.getText();

                    w.setForeground(Color.BLACK);
                    w.setBackground(Color.WHITE);  

                    BufferedWriter output = null;
                    FileInputStream fs = null;
                    FileWriter fout = null;

                    try {
                        // TODO add your handling code here:
                        File desktop = new File(System.getProperty("user.home"), "Desktop");
                       // Double total = Double.parseDouble(ba) + Double.parseDouble(fr) ;
                        File dir = new File (desktop + "/WattCPC");
                        if(!dir.exists()){
                            dir.mkdirs();
                        }
                        File myFile = new File(desktop + "/WattCPC/topextimechwidth.txt");
                        if(!myFile.exists()) {
                            myFile.createNewFile();
                        } 
                        fs = new FileInputStream(desktop + "/WattCPC/topextimechwidth.txt");
                        BufferedReader br = new BufferedReader(new InputStreamReader(fs));
                        output = new BufferedWriter(new FileWriter(myFile,true));
                        PrintWriter fileout = new PrintWriter(output,true);
                        if (br.readLine() == null) {
                               fileout.println("Model" + "," + "Date" + "," + "Line" + "," + "Shift" + "," + "Unit Number" + "," + "Width");
                         }
                        DateFormat dateFormat = new SimpleDateFormat("MMM/dd/yyyy hh:mm");
                        Date date = new Date();
                        for(int i = 1; i<100; ++i){
                            String linez = br.readLine();
                            if(linez==null){
                               fileout.println(model.getSelectedItem() + "," + dateFormat.format(date) + "," + line.getSelectedItem() + "," + shift.getSelectedItem() + "," + unitno.getText() + "," + ws  );
                               break;
                            }
                        }        
                    } catch (IOException ex) {
                        Logger.getLogger(setup.class.getName()).log(Level.SEVERE, null, ex);
                    } finally {
                        try {
                            output.close();
                        } catch (IOException ex) {
                            Logger.getLogger(setup.class.getName()).log(Level.SEVERE, null, ex);
                        }
                    }
                    JOptionPane msg = new JOptionPane("Saved successfully", JOptionPane.INFORMATION_MESSAGE);
                    final JDialog dlg = msg.createDialog("Message");
                    dlg.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
                    new Thread(new Runnable() {    

Answer 1

Some look and feels (looking at you Metal) use the Space key as the "action key". A simple solution would be to use a different look at feel, personally, I prefer the system look and feel for this reason, it should work in ways that the user is use to for the current system.

The "action" key will call all the registered ActionListener s when triggered

If, for some reason, you are unable to change the look and feel, you could use add a key binding to the JButton

JButton press = new JButton("Press me");
InputMap im = press.getInputMap(WHEN_FOCUSED);

im.put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0, false), "pressed");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0, true), "released");

A JButton already has a registered key binding called pressed and released which is generally configured for the default "action" key, what this does is simply reuses that, so that when you press the default "action" key OR Enter key, they will do the same thing, you don't need to do any extra coding.

See How to Use Key Bindings

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.InputMap;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.KeyStroke;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());

            JButton press = new JButton("Press me");
            InputMap im = press.getInputMap(WHEN_FOCUSED);

            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0, false), "pressed");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0, true), "released");

            press.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    JOptionPane.showMessageDialog(TestPane.this, "You rang master?");
                }
            });

            add(press);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

}

This is cumbersome, as you will either need to do this for every JButton you have, create a custom JButton and use that instead or provide some kind of factory method to perform the configuration for you, none of which are particular pleasant solutions.

The other solution you have is to create your own look and feel delegate and replace the default delegate. This is not pretty and has it's own issues which need to be considered (like which delegate do you extend from, what happens if the look and feel is changed?)

Answer 2

Use key binding to register the pressing of Enter key to the JButton as shown below:

KeyStroke enterKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_ENTER);
String action = "Enter"
Action enterAction = new AbstractAction(ActionEvent evt){
    @Override
    public void actionPerformed(ActionEvent e) {
        jButton1ActionPerformed(evt);
    }
};
jButton1.getInputMap(WHEN_FOCUSED).put(enterKeyStroke, action);
jButton1.getActionMap().put(action, enterAction);

I hope this will solve your problem.

Answer 3

See https://stackoverflow.com/a/16923982/1614775 . It suggests

UIManager.put("Button.defaultButtonFollowsFocus", Boolean.TRUE);