如何以编程方式确定不同键盘布局上“Ctrl + Plus”和“Ctrl + Minus”的正确击键？

Question

I'm trying to bind Ctrl + + and Ctrl + - to zoom in / out actions.

This question explains that on some keyboard layouts, + and - exist on the primary layer, whereas on others they exist on the secondary layer (you have to press a modifier key like Shift to type it). Also see bugs 4262044 and 6942481 .

Currently it looks like I have to analyze all layouts I want to support, and configure different key stroke bindings depending on the current layout, eg:

import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.KeyStroke;
import javax.swing.WindowConstants;

public class KeyStrokeTest extends JFrame {
  public static void main(String[] args) throws Exception {

    JFrame frame = new JFrame();

    // en_US
    register(frame, "control shift EQUALS");
    register(frame, "control MINUS");

    // de_DE
    //    register(frame, "control PLUS");
    //    register(frame, "control MINUS");

    // de_CH
    //    register(frame, "control shift 1");
    //    register(frame, "control MINUS");

    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    frame.setSize(200, 200);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    frame.getRootPane().setFocusable(true);
    frame.getRootPane().requestFocusInWindow();
  }

  private static void register(JFrame frame, String keyStrokeDefinition) {
    KeyStroke keyStroke = KeyStroke.getKeyStroke(keyStrokeDefinition);
    String key = keyStrokeDefinition;
    frame.getRootPane().getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(keyStroke, key);
    frame.getRootPane().getActionMap().put(key, new TestAction(keyStrokeDefinition));
  }

  private static class TestAction extends AbstractAction {
    private String info;

    public TestAction(String info) {
      this.info = info;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
      System.out.println("Action performed: " + info);
    }
  }
}

Is there a way to figure out the correct keystroke programmatically for + and - for all (or most) layouts?

Answer 1

I couldn't figure out how to do it use Key Bindings.

As an alternative you can listen for all KeyEvents and handle your specific situation:

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

public class Control implements AWTEventListener
{
    private boolean isPressed;

    public Control()
    {
        long eventMask = AWTEvent.KEY_EVENT_MASK;
        Toolkit.getDefaultToolkit().addAWTEventListener( this , eventMask);
    }

    public void eventDispatched(AWTEvent e)
    {
        KeyEvent ke = (KeyEvent)e;

        if (ke.getKeyCode() == KeyEvent.VK_CONTROL)
            isPressed = e.getID() == KeyEvent.KEY_PRESSED;

        if (isPressed
        &&  e.getID() == KeyEvent.KEY_PRESSED
        &&  ke.getKeyChar() == '+')
            System.out.println("Zoom In");
    }

    private static void createAndShowGUI()
    {
        new Control();

        JTextField textField = new JTextField(20);
        textField.setFont( textField.getFont().deriveFont(24.0f) );

        JFrame frame = new JFrame("SSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( textField );
        frame.pack();
        frame.setLocationByPlatform( true );
        frame.setVisible( true );
    }

    public static void main(String[] args) throws Exception
    {
        java.awt.EventQueue.invokeLater( () -> createAndShowGUI() );
    }
}

However, it only works for the "+" and not the "-". For some reason the Ctrl + "-" doesn't generate a valid key character.

So my next attempt was to try to use the Robot to use different key presses to see what character is generated:

import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.reflect.*;

public class KeyboardMap
{
    private HashMap<String, KeyStroke> keyStrokes = new HashMap<>();

    private JTextField textField = new JTextField(10);
    private Robot robot;

    public KeyboardMap()
    {
        // Create dummy dialog for usage by the Robot

        JDialog dialog = new JDialog();
//      dialog.setLocation(-200, -200);
        dialog.add( textField );
        dialog.pack();
        dialog.setVisible(true);

        try
        {
            robot = new Robot();
            robot.delay(32);

            ArrayList<Integer> keyCodes = getKeyCodes();

            for (Integer keyCode: keyCodes)
            {
                System.out.println(keyCode);
                generateCharacter(keyCode, false);
                generateCharacter(keyCode, true);
            }
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

    }

    private ArrayList<Integer> getKeyCodes() throws Exception
    {
        ArrayList<Integer> keyCodes = new ArrayList<>();
        keyCodes.add( KeyEvent.VK_0 );
        keyCodes.add( KeyEvent.VK_1 );
        keyCodes.add( KeyEvent.VK_2 );
        keyCodes.add( KeyEvent.VK_3 );
        keyCodes.add( KeyEvent.VK_4 );
        keyCodes.add( KeyEvent.VK_5 );
        keyCodes.add( KeyEvent.VK_6 );
        keyCodes.add( KeyEvent.VK_7 );
        keyCodes.add( KeyEvent.VK_8 );
        keyCodes.add( KeyEvent.VK_9 );
//      keyCodes.add( KeyEvent.VK_PLUS );
//      keyCodes.add( KeyEvent.VK_ADD );
        keyCodes.add( KeyEvent.VK_EQUALS );
        keyCodes.add( KeyEvent.VK_MINUS );

        return keyCodes;
    }

    private ArrayList<Integer> getKeyCodes2() throws Exception
    {
        ArrayList<Integer> keyCodes = new ArrayList<>();

        Field[] fields = KeyEvent.class.getFields();

        for (Field field: fields)
        {
            if (field.getName().startsWith("VK_"))
            {
                int keyCode = field.getInt(null);
                System.out.println(keyCode + " : " + field.getName());

//              if (keyCode < 1000)
                if (field.getName().length() == 4)
                {
                    keyCodes.add( keyCode );
//                  System.out.println(field.getName());
                }
            }
        }

        return keyCodes;
    }

    private void generateCharacter(int keyCode, boolean useShift)
    {
        if (useShift) robot.keyPress( KeyEvent.VK_SHIFT );

        robot.keyPress( keyCode );
        robot.keyRelease( keyCode );

        if (useShift) robot.keyRelease( KeyEvent.VK_SHIFT );

        robot.delay(50);

        String text = textField.getText();
//      System.out.println(keyCode + " : " + useShift + " : " + text);
        textField.setText("");

        if (text.length() == 1)
        {
            int modifier = (useShift) ? KeyEvent.SHIFT_DOWN_MASK : 0;

            KeyStroke ks = KeyStroke.getKeyStroke(keyCode, modifier);

            keyStrokes.put(text, ks);
        }
    }

        public KeyStroke getKeyStroke(String character)
        {
            return keyStrokes.get(character);
        }

    public static void main(String[] args) throws Exception
    {
        KeyboardMap map = new KeyboardMap();
        System.out.println(map.getKeyStroke("0"));
        System.out.println(map.getKeyStroke(")"));
        System.out.println(map.getKeyStroke("1"));
        System.out.println(map.getKeyStroke("!"));
        System.out.println(map.getKeyStroke("+"));
        System.out.println(map.getKeyStroke("-"));
    }
}

However this approach has timing issues. I tried to add delays to the various steps, which did seem so help.

Neither approach solves your problem, but it may give you some ideas?

Answer 2

This covers typing a 'plus' by any means which include pressing down CTRL or CTRL SHIFT:

register(f, "control MINUS");
register(f, "control SUBTRACT"); // minus on the numpad
// this covers typing a 'plus' by any means which include pressing down CTRL or CTRL SHIFT
f.getRootPane().addKeyListener(new KeyAdapter() {
    @Override
    public void keyPressed(KeyEvent evt) {
        String name = "control (shift) +";
        int mods = evt.getModifiersEx();
        if (mods == KeyEvent.CTRL_DOWN_MASK
                || mods == (KeyEvent.CTRL_DOWN_MASK | KeyEvent.SHIFT_DOWN_MASK)) {
            if (evt.getKeyChar() == '+') {
                System.out.println("Action performed: " + name);
            }
        }
    }
});

Answer 3

I eventually went with a modified version of thgw's answer.

On keyboard layouts where + or - is on the

• primary layer, it triggers for both Ctrl and Ctrl + Shift .

• secondary (Shift) layer, it triggers just for Ctrl + Shift .

Works for the numpad add and subtract keys as well.

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

public class Test {
  public static void main(String[] args) throws Exception {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    frame.setSize(600, 400);
    frame.setLocationByPlatform(true);
    frame.setVisible(true);

    frame.addKeyListener(new KeyAdapter() {
      @Override
      public void keyPressed(KeyEvent e) {
        if(e.getModifiersEx() == InputEvent.CTRL_DOWN_MASK //
            || e.getModifiersEx() == (InputEvent.CTRL_DOWN_MASK | InputEvent.SHIFT_DOWN_MASK)) {

          if(e.getKeyChar() == '+' || e.getKeyCode() == KeyEvent.VK_PLUS) {
            System.out.println("zoom in");
          }

          if(e.getKeyChar() == '-' || e.getKeyCode() == KeyEvent.VK_MINUS) {
            System.out.println("zoom out");
          }
        }
      }
    });
  }
}