SwingUtilities.convertPoint () returns negative values

Question

I ran into this problem in another project that has a complex JPanels structure and a lot of code.

It has the following snippet

Point point = label.getLocation(); Point point2 = SwingUtilities.convertPoint(label.getParent(), point, panel); 

in which the shortcut and panel are selected dynamically, and JLabel should be grandiose -... - a child of JPanel.

So, why the question is, in which case SwingUtilities.convertPoint() can return negative values ​​if the source and destination are parent-parent? Is this even possible?

This code shows a negative coordinate problem, but panel22 is not the label parent.

 import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Point; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.SwingUtilities; public class NegativeLocation { public static void main(String[] args) { new NegativeLocation(); } public NegativeLocation() { EventQueue.invokeLater(new Runnable() { @Override public void run() { JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLayout(new BorderLayout()); JPanel panel1 = new JPanel() { @Override public Dimension getPreferredSize() { return new Dimension(600, 400); } }; JPanel panel21 = new JPanel() { @Override public Dimension getPreferredSize() { return new Dimension(300, 400); } }; panel1.add(panel21); JPanel panel22 = new JPanel() { @Override public Dimension getPreferredSize() { return new Dimension(300, 400); } }; panel1.add(panel22); JPanel panel3 = new JPanel() { @Override public Dimension getPreferredSize() { return new Dimension(300, 400); } }; panel21.add(panel3); JLabel label = new JLabel("Label"); panel3.add(label); frame.getContentPane().add(panel1); frame.setPreferredSize(new Dimension(600, 400)); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); Point point = label.getLocation(); Point point2 = SwingUtilities.convertPoint(label.getParent(), point, panel21); Point point3 = SwingUtilities.convertPoint(label.getParent(), point, panel22); System.out.println(point2); System.out.println(point3); } }); } } 

Thus output

 java.awt.Point[x=134,y=10] java.awt.Point[x=134,y=-395] 

UPD: Basically, I need to find the location of the label relative to panel21 . How to change this line to achieve it?

 Point point = label.getLocation(); Point point2 = SwingUtilities.convertPoint(label.getParent(), point, panel21); 

Answer 1

Take the following example ...

 public class TestLocation01 { public static void main(String[] args) { new TestLocation01(); } public TestLocation01() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { } JPanel outter = new JPanel(new BorderLayout()); outter.setBorder(new CompoundBorder(new LineBorder(Color.RED), new EmptyBorder(10, 10, 10, 10))); JPanel inner = new JPanel(new GridBagLayout()); inner.setBorder(new CompoundBorder(new LineBorder(Color.BLUE), new EmptyBorder(10, 10, 10, 10))); JLabel label = new JLabel("Testing"); inner.add(label); outter.add(inner); JLabel below = new JLabel("Below"); JFrame frame = new JFrame("Test"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLayout(new BorderLayout()); frame.add(outter); frame.add(below, BorderLayout.SOUTH); frame.setSize(200, 200); frame.setLocationRelativeTo(null); frame.setVisible(true); System.out.println("lable.location: " + label.getLocation()); System.out.println("label to inner: " + SwingUtilities.convertPoint(label, new Point(0, 0), inner)); System.out.println("label to outter: " + SwingUtilities.convertPoint(label, new Point(0, 0), outter)); System.out.println("label.parent to inner: " + SwingUtilities.convertPoint(label.getParent(), new Point(0, 0), inner)); System.out.println("label.parent to outter: " + SwingUtilities.convertPoint(label.getParent(), new Point(0, 0), outter)); System.out.println("label to frame: " + SwingUtilities.convertPoint(label, new Point(0, 0), frame)); System.out.println("label.getParent to frame: " + SwingUtilities.convertPoint(label.getParent(), new Point(0, 0), frame)); System.out.println("outter to label: " + SwingUtilities.convertPoint(outter, new Point(0, 0), label)); System.out.println("label to below: " + SwingUtilities.convertPoint(label, new Point(0, 0), below)); System.out.println("below to label: " + SwingUtilities.convertPoint(below, new Point(0, 0), label)); } }); } } 

What generates (on my system) the following output

 lable.location: java.awt.Point[x=65,y=62] label to inner: java.awt.Point[x=65,y=62] label to outter: java.awt.Point[x=76,y=73] label.parent to inner: java.awt.Point[x=0,y=0] label.parent to outter: java.awt.Point[x=11,y=11] label to frame: java.awt.Point[x=76,y=95] label.getParent to frame: java.awt.Point[x=11,y=33] outter to label: java.awt.Point[x=-76,y=-73] label to below: java.awt.Point[x=76,y=-89] below to label: java.awt.Point[x=-76,y=89] 

If I pass the label as the source component, I get relative positions based on the relationship between the label and the component whose coordinate space I'm trying to transform. If I pass in the parent label element, instead I use the original coordinate space instead, which is associated with creating the wrong result

If you look at the relationship between label and below , it makes sense that you get negative results, since the label is above and to the right of below

Answer 2

This is the right behavior for me. Imagine the following. The main panel contains a child with the location x = 0 y = 100. If you convert the main panel 0,0 to a child, it returns us 0, -100. It doesn't really matter which component is the parent. The logic is to add (subtract all) all translate () calls that apply to the graphic when the parent makes the child.