Moving JComponent object based on mouse coordinates

[Chaz Branham]

I'm a little puzzled that when I create a basic JComponent and make it draggable by setting the location during the event it defaults and goes back to the original location once I let go of the mouse button and move the mouse. Can anyone kindly lead me in the right direction on what to do?

Below is my custom Component code.

package manning;
import javax.swing.*;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.dnd.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Rectangle2D;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;

public class DndCommandButton extends JComponent implements MouseListener, MouseMotionListener{
	//private JComponent component;
	private int Left;
	private int Top;
	private int Width;
	private int Height;
	private Rectangle2D Person = new Rectangle2D.Double(0,0,0,0);
	private volatile int screenX = 0;
	private volatile int screenY = 0;
	private volatile int myX = 0;
	private volatile int myY = 0;
	private int pCount;
	
	public DndCommandButton(int T, int L, int W, int H){
		Left = L;
		Top = T;
		Width = W;
		Height = H;
		this.addMouseListener(this);
		this.addMouseMotionListener(this);
		
	}
	
	public void paint(Graphics g){
		
		Graphics2D g2d = (Graphics2D) g;
		
		Person.setRect(Left, Top, Width, Height);
		g2d.setColor(Color.BLUE);
		g2d.fill(Person);
		pCount++;
		System.out.println("Painted: " + pCount);
	}
	/*public void paintComponent(Graphics g) {
		g.create();
		g.drawRect(50, 50, 50, 50);
		g.setColor(Color.BLUE);
		g.dispose();
		//super.paintComponents(g);
		
	}*/

	@Override
	public void mouseClicked(MouseEvent e) {
		// TODO Auto-generated method stub
		if ((e.getButton()) == 1 && Person.contains(e.getX(), e.getY())){ //Left Click
			JOptionPane.showMessageDialog(null, "Just a test!");
		}else if ((e.getButton()) == 3 && Person.contains(e.getX(), e.getY())){ //Right  Click
			JOptionPane.showMessageDialog(null, "Right Click! YES!");
		}
	}

	@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 mousePressed(MouseEvent e) {
		// TODO Auto-generated method stub
		screenX = e.getXOnScreen();
        screenY = e.getYOnScreen();

        myX = getX();
        myY = getY();

	}

	@Override
	public void mouseReleased(MouseEvent e) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void mouseDragged(MouseEvent e) {
		// TODO Auto-generated method stub
		int deltaX = e.getXOnScreen() - screenX;
        int deltaY = e.getYOnScreen() - screenY;

        setLocation(myX + deltaX, myY + deltaY);

	}

	@Override
	public void mouseMoved(MouseEvent e) {
		// TODO Auto-generated method stub
		
		if (Person.contains(e.getX(), e.getY())){ 
			ManningProgram.setText("Moved at ["+
					e.getX()+ ", "+e.getY()+"]");
		}else{
			ManningProgram.setText("");
		}
		
	}
	
	
}

Thank you for your help and time,

TheChazm

[Rob Camick]

First of all, custom painting is done by overriding the paintComponent() method NOT the paint() method. Also, super.paintComponent() (without the "s") is done at the start of the method not the end.

goes back to the original location once I let go of the mouse button and move the mouse.

Sound like the parent container is using a LayoutManager. You need to use

panel.setLayout(null)

on the parent panel of the component. You will now be responsible for setting the size/location of any component added to the panel.

[Chaz Branham]

Thanks for the reply and while I have read the PaintComponent was the correct place to work with the object I believe I had tried working with it but couldn't make it work correctly for some reason. I'll try it again but as for the Layout manager I am not specifying any so does it adopt one automatically anyway? I had previously tried to set the layout to null but it would never show the component I was making so once I took that line out it showed up. I'll post my main panel code as it's very basic since I am just trying to get the hang of writing custom components.

Thanks again for all the help

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

public class ManningProgram {
	public static JLabel statusBar;
	public static void main(String[] args) {

		JFrame e = new JFrame();
		WindowFunctions W = new WindowFunctions();
		
		e.setSize(W.GetWidth(), W.GetHeight());
		statusBar = new JLabel();
		statusBar.setBackground(Color.white);
		e.getContentPane().add(statusBar, BorderLayout.SOUTH);
		
		DndCommandButton cmdButton = new DndCommandButton(100,100,100,100);
				
		e.add(cmdButton);
		e.setTitle("Fun");
		e.setVisible(true);
		
	}
		public static void setText(String S){
			statusBar.setText(S);
		}
	}

[Chaz Branham]

Yes as expected when I set the layout to null it no longer paints my custom control. Also I moved all the code from paint to paintcomponent and it worked this time so must have been something in my old code that I was experimenting with that caused it not to work earlier. The component still goes back to 100,100,100,100 which is where it was originally created at using the following line of code.

DndCommandButton cmdButton = new DndCommandButton(100,100,100,100);

So long story short I still am having the same problem as before.

Thanks for your help and if you offer additional comments or help to resolve this it would greatly be appreciated.

My goal is that the object stays where I drag and let it go at.

[Rob Camick]

as for the Layout manager I am not specifying any so does it adopt one automatically anyway?

Your component is added to the content pane (which is just a JPanel) of the frame. The default LayoutManager for the content pane is a BorderLayout. So the size of you component is set to be whatever space is available in the frame (minus the space used for the borders and titlebar). That is the only reason your component displays.

Yes as expected when I set the layout to null it no longer paints my custom control.

I already explained what you need to do in my first reply in order to get a component to display when using a null layout.

The component still goes back to 100,100,100,100 which is where it was originally created

No, the component is displayed at location (0, 0). Your custom painting takes places at (100, 100). This is NOT the way to create a custom component. Your painting should be done at (0, 0) with a size of (100, 100). Now when you drag the component around the screen you just change the location of the component, but you need to use a null layout otherwise the layout manager will keep resetting the location to (0, 0).

Read the Swing tutorial on Custom Painting for an explanation and example of how to create a custom component. You should also be overriding the getPreferredSize() method to specify the size of your component.

[Chaz Branham]

Ok I think I understand most of that with the exception of the location being at (0, 0). Are you saying that since it has a BorderLayout then that is the border Layouts (0,0) position not the actual frame correct? The reason I brought up the 100,100,100,100 dimensions is that if I change it to 50,50,100,100 or 500,500,100,100 it does paint the component at those positions and does return the component to those locations in the frame. This is why I am a little confused about the (0,0) statement.

Please forgive me as I am just trying to understand and am not in any way trying to test or bother you in any way.

Thank you for being patiant with me. Thank you for the reference.

[Rob Camick]

Read the Swing tutorial on LayoutManagers. I gave you the link to the tutorial, search the table of contents for the layout tutorial.

One of the jobs of a layout manager is to position a component within the panel. This is done invoking the setLocation() method on the component. In your case you are adding the component to the CENTER of the BorderLayout. Since it is the only component added to the content pane it will be displayed at location (0, 0). You can verify this by displaying the bounds of your component AFTER the frame has been made visible.

if I change it to 50,50,100,100 or 500,500,100,100 it does paint the component at those positions

All Swing painting is done relative to the component, in the first case at (50, 50). Your component is located at (0, 0) of the content pane so the painting looks like it is being painted at (50, 50). If however you more your component to location (100, 100) then your painting is still done at (50, 50) but it will look like it is done at (150, 150) relative to the content pane.

[Chaz Branham]

Thank you for taking the time to help me understand. I will continue to look at the tutorials and really read up on Border Layouts. Appreciate it and I'm going to mark this as resolved as the rest is just a learning step for myself.

Have a good one