Java Community | Help. Code. Learn.•12mo ago

How does KeyListener work?

I have two(relevant) classes which ive made trying to figure out how this works.

package com.blockgoblin31.game;

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

public class Main {
    public static int xSize;
    public static int ySize;
    public static void main(String[] args) {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        JTextArea area = new JTextArea();
        JScrollPane pane = new JScrollPane(area);
        pane.setPreferredSize(new Dimension(375, 125));
        area.setEditable(false);
        frame.getContentPane().add(pane);
        Game game = new Game(area, frame);
        frame.addKeyListener(game);
        frame.pack();
        frame.setVisible(true);
        System.out.println("running");
    }
}

package com.blockgoblin31.game;

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

public class Main {
    public static int xSize;
    public static int ySize;
    public static void main(String[] args) {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        JTextArea area = new JTextArea();
        JScrollPane pane = new JScrollPane(area);
        pane.setPreferredSize(new Dimension(375, 125));
        area.setEditable(false);
        frame.getContentPane().add(pane);
        Game game = new Game(area, frame);
        frame.addKeyListener(game);
        frame.pack();
        frame.setVisible(true);
        System.out.println("running");
    }
}

package com.blockgoblin31.game;

import com.blockgoblin31.game.input.KeyContainer;

import javax.swing.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.WindowEvent;

public class Game implements KeyListener {

    private JTextArea area;

    private JFrame frame;

    public Game(JTextArea area, JFrame frame) {
        this.area = area;
        this.frame = frame;
    }

    public boolean close = false;

    @Override
    public void keyTyped(KeyEvent e) {
        turn(new KeyContainer(e));
        System.out.println("Text");
    }

    @Override
    public void keyPressed(KeyEvent e) {

    }

    @Override
    public void keyReleased(KeyEvent e) {

    }

    public void turn(KeyContainer key) {
        if (key.isKey("A")) {
            area.append("A Pressed");
            area.setCaretPosition(area.getDocument().getLength());
        }
        else if (key.isKeyCombination("C", new KeyContainer.ModifierType[]{KeyContainer.ModifierType.CONTROL})) frame.dispatchEvent(new WindowEvent(frame, WindowEvent.WINDOW_CLOSING));
    }
}

package com.blockgoblin31.game;

import com.blockgoblin31.game.input.KeyContainer;

import javax.swing.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.WindowEvent;

public class Game implements KeyListener {

    private JTextArea area;

    private JFrame frame;

    public Game(JTextArea area, JFrame frame) {
        this.area = area;
        this.frame = frame;
    }

    public boolean close = false;

    @Override
    public void keyTyped(KeyEvent e) {
        turn(new KeyContainer(e));
        System.out.println("Text");
    }

    @Override
    public void keyPressed(KeyEvent e) {

    }

    @Override
    public void keyReleased(KeyEvent e) {

    }

    public void turn(KeyContainer key) {
        if (key.isKey("A")) {
            area.append("A Pressed");
            area.setCaretPosition(area.getDocument().getLength());
        }
        else if (key.isKeyCombination("C", new KeyContainer.ModifierType[]{KeyContainer.ModifierType.CONTROL})) frame.dispatchEvent(new WindowEvent(frame, WindowEvent.WINDOW_CLOSING));
    }
}

21 Replies

JavaBot•12mo ago

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Hey @blockgoblin31! Please use /close or the Close Post button above when your problem is solved. Please remember to follow the help guidelines. This post will be automatically closed after 300 minutes of inactivity.

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blockgoblin31OP•12mo ago

Running prints and the window is created but after that nothing else happens most of this is me trying random stuff from the tutorial linked from the KeyListener page on the oracle docs

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

Ive done that frame.addKeyListener(game); line 18 of the first giant code block

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

yes, that line is called(the println for "running" works), but none of the other printlns ive scattered around work say the one in keyTyped

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

It also didn’t work when I didn’t have any other components Just the jframe and keylistener

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

so what here would be focusable? I tried adding the listener to the JScrollPane and JTextArea too in the example they added it to a JTextField, which makes sense I guess though I thought I tried that and it didnt work ok when I do that it works now... Is there a way to get it to work without needing a textbox?

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

I've been looking at that, when I said "the tutorial" I meant the file linked at the bottom there and I dont understand how I'd convert an Action into code somewhere else with key bindings, or what an Action is really

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

ok thanks I'll try that out, but tomorrow, Ive done too much coding already today

JavaBot•12mo ago

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blockgoblin31OP•12mo ago

so I've now tried doing it with keybindings, which is way nicer, but I can't figure out why one keybind works and the other doesnt

        pane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0), "a");
        pane.getActionMap().put("a", new KeyAction(game, "a"));
        pane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_C, InputEvent.CTRL_DOWN_MASK), "ctrl+c");
        pane.getActionMap().put("ctrl+c", new KeyAction(game, "c", new KeyContainer.ModifierType[]{KeyContainer.ModifierType.CONTROL}));

        pane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_A, 0), "a");
        pane.getActionMap().put("a", new KeyAction(game, "a"));
        pane.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_C, InputEvent.CTRL_DOWN_MASK), "ctrl+c");
        pane.getActionMap().put("ctrl+c", new KeyAction(game, "c", new KeyContainer.ModifierType[]{KeyContainer.ModifierType.CONTROL}));

so with this the first action works but the second doesnt I've confirmed with debugger only the first one is getting triggered

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

oh yep that was it, worked fine with b

Unknown User•12mo ago

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blockgoblin31OP•12mo ago

Maybe thats left alone because the focused component is a textbox, so it uses copy instead of passing it on either way ty again

JavaBot•12mo ago

Post Closed

This post has been closed by <@501514065068294154>.

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How does KeyListener work?