almal almal - 5 months ago 25
Java Question

Java nested class dont react to MouseListener events

in Java i'm try to create a class for display into a JFrame two JPanel components and add a Mouselistener at one of that.
I create a main JPanel and nested into it a private class named drawRec (JPanel type) used for draw a rectangle who should handle the mouse events over him but when I make a click, nothing happens. here is my code:

public class Exercise2 extends JPanel {

private drawRec square;


public static void main(String[] args) {
JFrame wind = new JFrame();
Exercise2 content = new Exercise2();
wind.setContentPane(content);
wind.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
wind.setLocation(100, 100);
wind.setSize(new Dimension(500,500));
wind.setVisible(true);

}

Exercise2() {
setBackground(Color.BLACK);
square = new drawRec();
}

public void paintComponent(Graphics g) {

super.paintComponent(g);
square.draw(g, 100, 90);
}

private class drawRec extends JPanel implements MouseListener {


drawRec() {
addMouseListener(this);
}

private void draw(Graphics g, int x, int y) {

g.setColor(Color.BLUE);
g.fillRect(x, y, 50, 20);


}

public void mouseClicked(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}

public void mousePressed(MouseEvent e) {
System.out.println("Test");
}

public void mouseReleased(MouseEvent e) {}

}
}


Thanks in advance

Answer

Your frame doesn't contain a drawRec panel. It contains an Exercise2 panel that calls drawRec.draw() to paint its content. If you click, you are clicking in an Exercise2 panel, which does not have a mouse listener.

Perhaps you should merge these two classes. At least you must add the mouse listener to a component that is actually added to the frame.

The shortest fix might be:

Exercise2() {
    setBackground(Color.BLACK);
    square = new drawRec();
    this.addMouseListener(square); // add this line
}

In that case you are still not using drawRec as a panel (because you are not adding it to anything), but you can use it as a mouse listener for your Exercise2 panel.