FlowLayoutlayout manager.When run this program will show a window with options for a FlowLayout at the top. A radio button group for the alignment and a couple of drop downs for horizontal and vertical spacing values. The "Set Layout" button will change the properties of the FlowLayout manager of the JPanel containing three JButtons.
The article relating to this program is Using the FlowLayout. There is another example program called GoingWithTheFlow which looks at the effect of changing the component orientation on the
FlowLayout.Note: To run the Java code this program should be saved in a file called
FlowLayoutExample.java//Imports are listed in full to show what's being used//could just import javax.swing.* and java.awt.* etc..import java.awt.EventQueue;import java.awt.FlowLayout;import java.awt.BorderLayout;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.JButton;import javax.swing.JRadioButton;import javax.swing.ButtonGroup;import javax.swing.JComboBox;import javax.swing.JLabel;import java.awt.event.ActionListener;import java.awt.event.ActionEvent;public class FlowLayoutExample {JFrame guiFrame;JPanel buttonPanel;JComboBox hGap;JComboBox vGap;JRadioButton leftAlign;JRadioButton rightAlign;JRadioButton centerAlign;//Note: Typically the main method will be in a//separate class. As this is a simple one class//example it's all in the one class.public static void main(String[] args) {//Use the event dispatch thread for Swing components EventQueue.invokeLater(new Runnable() { @Override public void run() {new FlowLayoutExample();} });}public FlowLayoutExample(){guiFrame = new JFrame();//make sure the program exits when the frame closesguiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);guiFrame.setTitle("FlowLayout Example");guiFrame.setSize(700,300);//This will center the JFrame in the middle of the screenguiFrame.setLocationRelativeTo(null);//The optionpanel uses the FlowLayout in its default form//to show the options (i.e., align = center, vgap = 5, hgap = 5)JPanel optionPanel = new JPanel();FlowLayout f = (FlowLayout)optionPanel.getLayout();System.out.println(f.getHgap() + "v:" + f.getVgap());leftAlign = new JRadioButton("Left");leftAlign.setActionCommand("Left");rightAlign = new JRadioButton("Right");rightAlign.setActionCommand("Right");centerAlign = new JRadioButton("Center");centerAlign.setActionCommand("Center");centerAlign.setSelected(true);//Group the radio buttons.ButtonGroup group = new ButtonGroup();group.add(leftAlign);group.add(rightAlign);group.add(centerAlign);optionPanel.add(leftAlign);optionPanel.add(centerAlign);optionPanel.add(rightAlign);Integer[] options = {0,20,40,60,80,100};hGap = new JComboBox(options);hGap.setSelectedIndex(0);vGap = new JComboBox(options);vGap.setSelectedIndex(0);JLabel horizontalGap = new JLabel("Horizontal Gap:");JLabel verticalGap = new JLabel("Vertical Gap:");JButton setLayout = new JButton("Set Layout");setLayout.setActionCommand("Set Layout");setLayout.addActionListener(new ActionListener(){@Overridepublic void actionPerformed(ActionEvent event){//create a new FlowLayout based on the options selected//and give it to the buttonPanel.FlowLayout flow = new FlowLayout();flow.setHgap((Integer)hGap.getSelectedItem());flow.setVgap((Integer)vGap.getSelectedItem());int alignment = FlowLayout.CENTER;if (leftAlign.isSelected()){alignment = FlowLayout.LEFT;}else if (rightAlign.isSelected()){alignment = FlowLayout.RIGHT;}flow.setAlignment(alignment);buttonPanel.setLayout(flow);buttonPanel.revalidate();buttonPanel.repaint();}});optionPanel.add(horizontalGap);optionPanel.add(hGap);optionPanel.add(verticalGap);optionPanel.add(vGap);optionPanel.add(setLayout);buttonPanel = new JPanel();//example buttons to show how the layout of //components changesJButton button1 = new JButton("Button One");button1.setActionCommand("Button One");JButton button2 = new JButton("Button Two");button2.setActionCommand("Button Two");JButton button3 = new JButton("Button Three");button3.setActionCommand("Button Three");buttonPanel.add(button1);buttonPanel.add(button2);buttonPanel.add(button3);guiFrame.add(optionPanel, BorderLayout.NORTH);guiFrame.add(buttonPanel, BorderLayout.SOUTH);guiFrame.setVisible(true);}}