Learning Java, 4th Edition

FlowLayout

FlowLayout is a simple layout manager that tries to arrange components at their preferred sizes, from left to right and top to bottom in the container. A FlowLayout can have a specified row justification of LEFT, CENTER, or RIGHT and a fixed horizontal and vertical padding. By default, a flow layout uses CENTER justification, meaning that all components are centered within the area allotted to them. FlowLayout is the default for JPanels.

The following example adds five buttons to the content pane of a JFrame using the default FlowLayout:

    //file: Flow.java
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;

    public class Flow extends JPanel {

      public Flow() {
        // FlowLayout is default layout manager for a JPanel
        add(new JButton("One"));
        add(new JButton("Two"));
        add(new JButton("Three"));
        add(new JButton("Four"));
        add(new JButton("Five"));
      }

      public static void main(String[] args) {
        JFrame frame = new JFrame("Flow");
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

        frame.setSize(400, 75);
        frame.setLocation(200, 200);
        Flow flow = new Flow();
        frame.setContentPane(flow);
        frame.setVisible(true);
      }
    }

The result is shown in Figure 19-2.

Figure 19-2. A flow layout

Try resizing the window. If it is made narrow enough, some of the buttons will spill over to a second or third row.