How do I use GridBagLayout

Question

I have have a JLabel, a JButton and a JTextField; I need to put the JLabel in cell (0,0) from the JFrame origin and then put a JTextField (1,0) and finally put a JButton (0,1) on the second line. But, all my components are put in the same row and they start from left to right.

My code:

public static  void initializeFrame(){
  GridBagLayout layout  = new GridBagLayout();
  // set frame layout      
  JFrame frame = new JFrame("JFrame Source Demo");
  frame.setSize(new Dimension(400,200));
  frame.setLayout(new GridBagLayout());
  GridBagConstraints c = new GridBagConstraints();
  c.fill = GridBagConstraints.HORIZONTAL;
  JPanel    topPanel = new JPanel();
  JLabel jlbempty = new JLabel("MacAddress");
  c.gridx = 0;
  c.gridy = 0;
  c.ipadx = 30;
  c.ipady = 10;
  topPanel.add(jlbempty,c);
  JTextField field1 = new JTextField();
  c.gridx = 1;   
  c.gridy = 0;
  c.ipadx = 30;
  c.ipady = 10;
  topPanel.add(field1,c);
  field1.setPreferredSize(new Dimension(150, 20));
  JButton jb = new JButton("Generation Mac");
  c.gridx = 0;
  c.gridy = 1;
  c.ipadx = 30;
  c.ipady = 10; 
  layout.setConstraints( jb, c ); // set constraints
  topPanel.add(field1,c); 
  topPanel.add(jb,c);
  frame.add(topPanel);
  frame.pack();
  frame.setVisible(true);
}

Answer 1

Some of the things that I observed in your code.

• Set layout of the topPanel to GridBagLayout.

• You are calling topPanel.add(field1, c); two times.

• Don't use preferred size instead use relative size. Just hand over it to Layout manger to size the component.

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Read more about How to Use GridBagLayout for more clarity and find the sample code as well.

Please read more about the other properties of GridBagLayout.

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Here is the simplified code with inline comments.

GridBagConstraints c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
// c.insets=new Insets(5,5,5,5);   // margin outside the panel

JPanel topPanel = new JPanel(new GridBagLayout());

JLabel jlbempty = new JLabel("MacAddress");
c.gridx = 0;
c.gridy = 0;
// c.weightx=0.25;     // width 25% for 1st column
topPanel.add(jlbempty, c);

JTextField field1 = new JTextField();
c.gridx = 1;
c.gridy = 0;
// c.weightx=0.75;     // width 75% for 2nd column
topPanel.add(field1, c);

JButton jb = new JButton("Generation Mac");
c.gridx = 0;
c.gridy = 1;
//c.gridwidth = 2;    //SPAN to 2 columns if needed
// c.weightx=1.0;     // back to width 100%
topPanel.add(jb, c);