GUI Components: Part 2 - Java: How to Program Early Objects - page 951

1 // Fig. 22.24: GridBagDemo2.java

2 // Demonstrating GridBagLayout constants.

3 import javax.swing.JFrame;

4
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public class GridBagDemo2

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{

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public static void main(String[] args)

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{

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GridBagFrame2 gridBagFrame = new GridBagFrame2();

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gridBagFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

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gridBagFrame.setSize( 300 , 200 );

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gridBagFrame.setVisible( true );

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}

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} // end class GridBagDemo2

Fig. 22.24 | Test class for GridBagDemo2 .

Setting the JFrame 's Layout to a GridBagLayout
Lines 21-22 create a GridBagLayout and use it to set the JFrame 's layout manager. The
components that are placed in GridBagLayout are created in lines 27-38—they are a
JComboBox , a JTextField , a JList and five JButton s.

Configuring the JTextField
The JTextField is added first (lines 41-45). The weightx and weighty values are set to
1. The fill variable is set to BOTH . Line 44 specifies that the JTextField is the last com-
ponent on the line. The JTextField is added to the content pane with a call to our utility
method addComponent (declared at lines 79-83). Method addComponent takes a Compo-
nent argument and uses GridBagLayout method setConstraints to set the constraints
for the Component . Method add attaches the component to the content pane.

Configuring JButton buttons[0]
JButton buttons[0] (lines 48-49) has weightx and weighty values of 1. The fill vari-
able is BOTH . Because buttons[0] is not one of the last two components on the row, it's
given a gridwidth of 1 and so will occupy one column. The JButton is added to the con-
tent pane with a call to utility method addComponent .