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Is there a way in Java to be able to click through a JFrame?

I'm trying to make an overlay for a HTML-based game running in a browser window and created an JFrame which is opaque. I'd like to be able to still play the game whilst having the overlay above the window. I tried some solutions that I've found but those didn't work for me.
I've thought of catching the click-event on my JFrame and "simulating" the click on the game window. But sadly I don't have an idea how thats possible.
My current code is using the JNA libarys to access the position and scale of the window (in my test code Task-Manager).
I'm fine with using another libary or something like that, if it's even possible.
Thats my code so far:
import com.sun.jna.platform.DesktopWindow;
import com.sun.jna.platform.WindowUtils;
import javax.swing.*;
import java.awt.*;
public class Test {
public static void main(String[] args) throws InterruptedException {
JFrame frame = new JFrame("title");
frame.setUndecorated(true);
frame.setBackground(new Color(255, 69, 0, 100));
frame.setAlwaysOnTop(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Rectangle rect = null;
while (true) {
for (DesktopWindow desktopWindow : WindowUtils.getAllWindows(true)) {
if (desktopWindow.getTitle().contains("Task-Manager")) {
rect = desktopWindow.getLocAndSize();
frame.setSize(rect.width - 16, rect.height - 8);
frame.setLocation(rect.x + 8, rect.y);
frame.setVisible(true);
Thread.sleep(10);
}
}
}
}
}

A JFrame is a heavyweight component. There is a window in the host OS GUI system to go with it. The host OS GUI directs mouse events to the window. Perhaps using a lightweight component for your overlay and then disabling mouse events on it would be a better solution.
Your idea of catching the click event and "simulating it" on you game window should be fairly easy. If your JFrame event processing code has a reference to your game engine, it can determine the relative position of the windows and tell your game engine the corresponding point at which it should act as if it received a click. I.e. just call the same method of your game engine for click events that it received normally and also for the simulated ones.
An ugly hack (there is noticeable flicker) would be to hide the window and send the click through with the Robot class... like this:
import java.awt.AWTException;
import java.awt.Color;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Robot;
import java.awt.event.InputEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.SwingUtilities;
public class ClickThrough extends Frame implements MouseListener, MouseMotionListener {
private final Robot robot;
private Color bgColor = new Color(0x80808080, true);
private Point dragPoint;
public ClickThrough() throws AWTException {
setAlwaysOnTop(true);
robot = new Robot();
}
public static void main(String[] args) throws AWTException {
ClickThrough w = new ClickThrough();
w.setUndecorated(true);
w.setSize(200, 100);
w.setOpacity(0.7f);
w.addMouseListener(w);
w.addMouseMotionListener(w);
w.setVisible(true);
}
#Override
public void paint(Graphics g) {
int w = getWidth();
int h = getHeight();
g.setColor(Color.GRAY);
g.fillRect(0, 0, w, 16);
g.setColor(bgColor);
g.fillRect(0, 16, w, h-16);
g.setColor(Color.BLACK);
g.drawString("Go ahead, click on me...", 20, 50);
}
private void makeHole(MouseEvent e) {
// Tried making a shape with a hole where the mouse was clicked,... didn't work (macOS).
//setShape(windowWithHoleShape);
setVisible(false);
}
private void repairHole(MouseEvent e) {
//setShape(windowShape);
setVisible(true);
}
#Override
public void mousePressed(MouseEvent e) {
Point p = e.getPoint();
// give it a draggable area at the top
if (p.y < 16) {
dragPoint = p;
return;
}
dragPoint = null;
SwingUtilities.convertPointToScreen(p,this);
makeHole(e);
robot.mouseMove(p.x, p.y);
robot.mousePress(InputEvent.getMaskForButton(e.getButton()));
repairHole(e);
}
#Override public void mouseReleased(MouseEvent e) { }
#Override public void mouseClicked(MouseEvent e) { }
#Override public void mouseEntered(MouseEvent e) { }
#Override public void mouseExited(MouseEvent e) { }
#Override
public void mouseDragged(MouseEvent e) {
if (dragPoint != null) {
Point p = e.getPoint();
SwingUtilities.convertPointToScreen(p, this);
p.translate(-dragPoint.x, -dragPoint.y);
setLocation(p);
}
}
#Override
public void mouseMoved(MouseEvent e) { }
}
I tried to see if I could cut a hole in the window by setting the window Shape, but at least on macOS the hole does not allow the mouse events through.
I should also point out that if you switch your GUI framework to JAvaFX, then you have the option of running your HTML-based game UI in a JavaFX WebView, so you can integrate your game and overlay into a single coherent application. You could specifically make your overlay "mouse transparent". IMO that would be a much better approach than hacking around with the mouse events.

How do I make a (keyPressed) KeyListener?

Im trying to write a very simple program that allows you to control a sprite with arrow keys and move around the screen. From what I understand, to do this I need a keyPressed() KeyListener. I believe Im doing this correctly based on the Java Doc but its not returning the correct output when I press the designated key. Can someone please tell me what is wrong with my code, and if possible, provide a simple example of the usage of this class? Thanks!
(Note, code is unfinished)
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
public class Display extends JPanel implements ActionListener, KeyListener {
Display() {
// super();
loadImages();
initTimer();
this.addKeyListener(this);
}
BufferedImage sprite;
Timer timer;
int up = 0;
public void loadImages() {
File spriteImage = new File("Pacman_sprite.png");
try {
sprite = ImageIO.read(spriteImage);
} catch (IOException e) {
System.out.println("Sprite import failed");
}
}
public void initTimer() {
timer = new Timer(100, this);
timer.start();
this.addKeyListener(this);
}
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
System.out.println("Key press registered"); //does not print this?
if (key == KeyEvent.VK_UP) {
System.out.println("sucess"); // does not print this?
up++;
repaint();
}
}
#Override
public void keyReleased(KeyEvent e) {
System.out.println("release");
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
setBackground(Color.WHITE);
Graphics2D g2d = (Graphics2D) g;
g2d.drawImage(sprite, 500, 500 + up, null);
}
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
repaint();
}
}
EDIT:
May have found the answer here. I moved the key handling code to a new class called KeyHandler then added these two lines to the constructor:
addKeyListener(new KeyHandler());
setFocusable(true);
It now appears to be working just fine (sort of, at least it is detecting when the up key is hit. My graphics aren't.)

You are not adding the listener to the JPanel.
Note: I would suggest you to change your design. Right now, Display class is both a JPanel and a Listener (which doesn't make sense in my opinion).
But to add the listener in your code do something like,
this.addKeyListener(this); // This looks awkward right. That's why you should change the design.
in your constructor.

Java: Repaint in Swing Not Working

I am learning java swing and am having trouble with the following program. It creates a small frame with a quit button at top. The objective is to display coordinates wherever the mouse is clicked. When I click the mouse 2 unwanted things are happening:
the quit button is overridden by the mouse clicks and it no longer responds (instead of responding to event and quitting, it displays coordinates on top of the quit button).
when I click at a new location, the coordinates from the old location persist.
I used removeAll() and revalidate() before doing repaint() based on this discussion but that has not helped. This code is taken from here and the code to says to research online documentation for why this is happening.
Any pointers?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.Color;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.BorderLayout;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JLabel;
public class QuitCoordinateTest {
public static void main(String[] args){
GUI gui = new GUI();
}
}
class MyFrame extends JFrame implements ActionListener{
int clickX;
int clickY;
public void paint(Graphics g){
g.drawString("" + clickX + ", " + clickY, clickX, clickY);
}
public void actionPerformed(ActionEvent e){
System.exit(0);
}
}
//=======================================================//
class GUI extends MyFrame {
JButton quitButton = new JButton("Quit");
public GUI(){
MyFrame displayWindow = new MyFrame();
displayWindow.setTitle("Title");
/*
JPanel buttonPanel = new JPanel();
buttonPanel.add(quitButton);
displayWindow.getContentPane().add(buttonPanel,BorderLayout.NORTH);
JPanel textPanel = new JPanel();
*/
displayWindow.getContentPane().add(quitButton,BorderLayout.NORTH);
quitButton.addActionListener(displayWindow);
displayWindow.setSize(201,201);
displayWindow.setVisible(true);
// displayWindow.pack();
displayWindow.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
displayWindow.addMouseListener(new MouseProc(displayWindow));
}//end constructor
}//end class GUI definition
//=======================================================//
//This listener class monitors for mouse presses and
// displays the coordinates of the mouse pointer when the
// mouse is pressed on the source object.
class MouseProc extends MouseAdapter{
MyFrame refToWin;
MouseProc(MyFrame inWin){
refToWin = inWin;
}
//Override the mousePressed method to determine and
// display the coordinates when the mouse is pressed.
public void mousePressed(MouseEvent e){
refToWin.removeAll();
refToWin.clickX = e.getX();
refToWin.clickY = e.getY();
//Force the JFrame object to be repainted in order to
// display the coordinate information.
refToWin.removeAll();
refToWin.validate();
refToWin.repaint();
}
}

repaint() is working fine.
Avoid drawing directly on the JFrame.
Instead draw in the protected void paintComponent(Graphics g) method override of a JPanel that is then displayed in your JFrame.
Be sure to call the super's paintComponent(g) method inside of your paintComponent override -- this will erase the old images and is the reason for one of your problems.
Use reasonable comments in your code. Too many comments and too much text distracts and makes understanding your code harder, not easier.
Calling removeAll() on your JFrame will do just that -- remove all components including your button. Why are you calling this? Are you sure that you want to call this method?
A minor nitpick -- you'll want to avoid directly setting the fields of another class, such as your clickX and clickY fields. Instead, make them private, and only allow outside classes to modify them through public methods. While it may not matter much for this small program, it will matter greatly when you start scaling up your programming and create large programs with complex interactions. The key to success here will be to limit and control all communication between classes to avoid hard to detect side effects.
For example, something like...
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
String str = String.format("[%d, %d]", clickX, clickY);
g.drawString(str, clickX, clickY);
}
public int getClickX() {
return clickX;
}
public void setClickX(int clickX) {
this.clickX = clickX;
}
public int getClickY() {
return clickY;
}
public void setClickY(int clickY) {
this.clickY = clickY;
}
For example
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;
#SuppressWarnings("serial")
public class DetectClicks extends JPanel {
private static final int PREF_W = 800;
private static final int PREF_H = 650;
private int clickX;
private int clickY;
public DetectClicks() {
MyMouseListener mouseAdapter = new MyMouseListener(this);
addMouseListener(mouseAdapter);
addMouseMotionListener(mouseAdapter); // to allow dragging!
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
String str = String.format("[%d, %d]", clickX, clickY);
g.drawString(str, clickX, clickY);
}
public int getClickX() {
return clickX;
}
public void setClickX(int clickX) {
this.clickX = clickX;
}
public int getClickY() {
return clickY;
}
public void setClickY(int clickY) {
this.clickY = clickY;
}
private static void createAndShowGui() {
DetectClicks mainPanel = new DetectClicks();
JFrame frame = new JFrame("DetectClicks");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class MyMouseListener extends MouseAdapter {
private DetectClicks detectClicks;
public MyMouseListener(DetectClicks detectClicks) {
this.detectClicks = detectClicks;
}
#Override
public void mousePressed(MouseEvent evt) {
showPoint(evt);
}
#Override
public void mouseDragged(MouseEvent evt) {
showPoint(evt);
}
private void showPoint(MouseEvent evt) {
detectClicks.setClickX(evt.getX());
detectClicks.setClickY(evt.getY());
detectClicks.repaint();
}
}

Your event is getting consumed by the handler that prints the coordinates, you need to redispatch the event so that the button can see it. You can do it like this, inside the coordinate display event handler:
Component c = e.getComponent();
c.getParent().dispatchEvent( e );
Also, I'd be tempted to use the glass pane of the frame, and put a JLabel on it with the co-ordinates rather than messing with the paint method.

you don't have to use any of repaint(),invalidate() etc.
i highly recommend to use
SwingUtilities.invokeLater(new Runnable() {
public void run() {
//TODO udpdate UI compontents, layouts etc.
}
});
this guarantees that UI components update on real time. Because we don't know when the system update UI hierarchy so we can't force it. This allow system to determine by it's self.

motion of rectangle by keyboard

I made the following code to move a rectangle using arrowkeys of keyboard. The "keyPressed" function does not seem to be working properly.Infact, i don't think it is even getting called when a key is pressed bcz when i tried to print some text when a key is pressed, it was not getting printed.All i see in the output window is a stationary rectangle fixed at the top left corner of the window.Here is my code....pls help me...i need it desperately
import javax.swing.JFrame;
public class Main
{
public static void main(String args[])
{
JFrame window=new JFrame();
window.setSize(600,400);
window.setTitle("window");
window.setVisible(true);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
drawingComponent DC=new drawingComponent();
window.add(DC);
}
}
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JComponent;
import javax.swing.Timer;
public class drawingComponent extends JComponent implements ActionListener,KeyListener
{
Timer t=new Timer(2000,this);//moving after 5 milliseconds
static int x=0;
static int y=0;
private static int velx=0;
private static int vely=0;
public drawingComponent()
{
t.start();
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
System.out.println("tr1");
}
public void paintComponent(Graphics g)
{
Graphics2D g2=(Graphics2D) g;
Rectangle rect1=new Rectangle(x,y,50,30);
g2.setColor(Color.RED);
g2.fill(rect1);
System.out.println("tr2");
}
public void actionPerformed(ActionEvent e) //inbuilt fncn f actionListener(interface) which needs to be created
{
x+=velx; //changing values
y+=vely;
System.out.println("tr3");
repaint(); //inbuilt fncn to repeat the paintComponent method
}
public void keyPressed(KeyEvent e)
{
int code=e.getKeyCode();
if(code==KeyEvent.VK_UP)
{ velx=0; vely=-1;repaint(); }
if(code==KeyEvent.VK_DOWN)
{ velx=0; vely=1; repaint(); }
if(code==KeyEvent.VK_LEFT)
{vely=0; velx=-1; repaint(); }
if(code==KeyEvent.VK_RIGHT)
{vely=0; velx=1; repaint();}
}
public void keyTyped(KeyEvent e)
{}
public void keyReleased(KeyEvent e)
{}
}

Welcome to the wonderful world of KeyListeners...
While you have set the component focusable, you've not requested that the component be focused.
You could try calling requestFocusInWindow, but he this raises the question of when to call it.
You could call it within the constructor, but because the component doesn't belong to a valid visible component yet, the call may fail. You could override the components addNotify method and add the call to it, after you call super.addNotify, but the requestFocusInWindow method doesn't gurentee that focus will be given the component
Instead, you could simply avoid all this hassle and use the key bindings API instead, which will give you control over the level of focus require for key events to be triggered
As a side note, you should call setVisible on your frame after you've set up the UI completely

Swing - Avoid line filling between different lines

I'm trying to get into Swing by developing a simple drawing application in Java.
The problem is that I'm using an array of Points to keep track on the mouseDragged event, but when I release the mouse button and I begin to draw a new line they get connected (previous line's last node to the first point of the new line).
I was thinking maybe to keep track of the Points listened by the mousePressed and mouseReleased listeners in another ArrayList, to know which are the begin and end points of every line and then, when it's time to draw the lines between the points, checking if they are in the ArrayList and avoid drawing that line.
What is your suggested approach? How can I implement this in my code? Thank you!
package ccdraw;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
import javax.swing.event.MouseInputListener;
#SuppressWarnings("serial")
public class DrawingArea extends JPanel implements MouseInputListener {
private ArrayList<Point> pointList = new ArrayList<Point>();
//private ArrayList<Point> beginEndPoints = new ArrayList<Point>();
public DrawingArea() {
super();
super.setPreferredSize(new Dimension(400,400));
setBorder(BorderFactory.createLineBorder(Color.black));
addMouseListener(this);
addMouseMotionListener(this);
}
public void paintComponent(Graphics g){
super.paintComponent(g);
doDrawing(g);
}
private void doDrawing(Graphics g){
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.RED);
g2d.setStroke(new BasicStroke(1.5f));
for (int i=1;i<pointList.size()-1;i++){
// here i should check when it changes between old and new line
// and don't draw the line between those two points!
//if(pointList.get(i).x - pointList.get(i+1).x <= 1 && pointList.get(i).y - pointList.get(i+1).y <= 1)
g2d.drawLine(pointList.get(i).x, pointList.get(i).y, pointList.get(i+1).x, pointList.get(i+1).y);
}
}
#Override
public void mouseClicked(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mousePressed(MouseEvent arg0) {
pointList.add(arg0.getPoint());
}
#Override
public void mouseReleased( MouseEvent arg0) {
pointList.add(arg0.getPoint());
repaint();
}
#Override
public void mouseDragged(MouseEvent arg0) {
pointList.add(arg0.getPoint());
repaint();
}
#Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mouseMoved(MouseEvent e) {
// TODO Auto-generated method stub
}
}

I was thinking maybe to keep track of the Points listened by the mousePressed and mouseReleased listeners in another arraylist,
Keep an ArrayList of ArrayLists.
So every time you do a mousePressed you start an new ArrayList for the series of Points to be added by the mouseDragged event.
Then in the painting code you iterate through the two ArrayLists. This should be easier than adding exception logic for the start/end points.
Another option is to do the drawing directly to a BufferedImage, so you don't need to keep track of the Points at all. Check out Custom Painting Approaches which compares these two general custom painting approaches to decide which approach is best for your requirment.