GridBagLayout错误地显示元素

Question

I'm currently writing a test function, that dynamically adds elements into JPanel on button click. I'm using GridBagLayout . Here is the code of my function:

 public void buildGui(){
       ConnectionInfoPanel.removeAll();
       //test first group of items
       listOfLabels.add(new JLabel("Label 1"));
       listOfLabels.add(new JLabel("Label 2"));
       listOfLabels.add(new JLabel("Label 3"));
       listOfLabels.add(new JLabel("Label 4"));

       GridBagConstraints c = new GridBagConstraints();
              c.weightx = 1;
              c.weighty = 1;
              c.insets = new Insets(10,10,10,10);
              c.anchor = GridBagConstraints.NORTHWEST;

        ConnectionInfoPanel.add(listOfLabels.get(0), c);
        ConnectionInfoPanel.add(new JLabel(), c);

        ConnectionInfoPanel.add(listOfLabels.get(1), c);
        ConnectionInfoPanel.add(new JLabel(), c);


        ConnectionInfoPanel.add(listOfLabels.get(2), c);
        ConnectionInfoPanel.add(new JLabel(), c);

        ConnectionInfoPanel.add(listOfLabels.get(3), c);
        ConnectionInfoPanel.add(new JLabel(), c);

       //test second group
       listOfLabels.add(new JLabel("Label 5"));
       listOfLabels.add(new JLabel("Label 6"));
       listOfLabels.add(new JLabel("Label 7"));
       listOfLabels.add(new JLabel("Label 8"));

       GridBagConstraints x = new GridBagConstraints();
              x.weightx = 1;
              x.weighty = 2;
              x.insets = new Insets(10,10,10,10);
             // x.anchor = GridBagConstraints.NORTHWEST;

        ConnectionInfoPanel.add(listOfLabels.get(4), x);
        ConnectionInfoPanel.add(new JLabel(), x);

        ConnectionInfoPanel.add(listOfLabels.get(5), x);
        ConnectionInfoPanel.add(new JLabel(), x);


        ConnectionInfoPanel.add(listOfLabels.get(6), x);
        ConnectionInfoPanel.add(new JLabel(), x);

        ConnectionInfoPanel.add(listOfLabels.get(7), x);
        ConnectionInfoPanel.add(new JLabel(), x);

        ConnectionInfoPanel.updateUI();
    }

In the first group of elements everything works fine. They lay into the line from top-left corner(0,0).

But in second group of elements their starting position becomes center of the panel(in Y-axis) and end of the Label4 (in X-axis). But what i'm trying to achieve is to set their starting position to (0, 1). So this group is displayed directly below first one. Can anyone show me what i'm doing wrong?

Answer 1

You need to set gridX and gridY values in your grid constraints or the layout manager has no idea where to put the components.

And I think you are also confusing weightX and weightY with gridX and gridY. The are two different things.

For each component reset the constraints like this :

GridBagConstraints c = new GridBagConstraints();

c.gridx = 0;
c.gridy = 0;


ConnectionInfoPanel.add(listOfLabels.get(0), c);
c.gridx++;
ConnectionInfoPanel.add(listOfLabels.get(1), c);
c.gridx++;
ConnectionInfoPanel.add(listOfLabels.get(2), c);
c.gridx++;
ConnectionInfoPanel.add(listOfLabels.get(3), c);

c.gridx = 0;
c.gridy = 1;


ConnectionInfoPanel.add(listOfLabels.get(4), c);
c.gridx++;
ConnectionInfoPanel.add(listOfLabels.get(5), c);
c.gridx++;
ConnectionInfoPanel.add(listOfLabels.get(6), c);
c.gridx++;
ConnectionInfoPanel.add(listOfLabels.get(7), c);

If you don't know how long the list is, then you need to add some loops which will continuously increment the y.

Alternatively you could add the two rows to two flowlaout panels, and then add this to a gridbaglaout panel like so :

JPanel panel1 = new JPanel();
panel1.add(listOfLabels.get(0));
panel1.add(listOfLabels.get(1));
panel1.add(listOfLabels.get(2));
panel1.add(listOfLabels.get(3));
ConnectionInfoPanel.add(panel1, c);


JPanel panel2 = new JPanel();
panel2.add(new JLabel("Label 5"));
panel2.add(new JLabel("Label 6"));
panel2.add(new JLabel("Label 7"));
panel2.add(new JLabel("Label 8"));

GridBagConstraints x = new GridBagConstraints();
x.weightx = 1;
x.weighty = 2;
x.insets = new Insets(10, 10, 10, 10);
// x.anchor = GridBagConstraints.NORTHWEST;

x.gridy = 0;
ConnectionInfoPanel.add(panel1, x);
x.gridy = 1;
ConnectionInfoPanel.add(panel2, x);