Trail: Creating a GUI With Swing
Lesson: Laying Out Components Within a Container
The Java Tutorials have been written for JDK 8. Examples and practices described in this page don’t take advantage of improvements introduced in later releases and might use technology no longer available. See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases. See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
How to Use FlowLayout
Note: This lesson covers writing layout code by hand, which can be challenging. If you are not interested in learning all the details of layout management, you might prefer to use the GroupLayout
layout manager combined with a builder tool to lay out your GUI. One such builder tool is the
GroupLayout
, then GridBagLayout
is recommended as the next most flexible and powerful layout manager.
This lesson covers writing layout code by hand, which can be challenging. If you are not interested in learning all the details of layout management, you might prefer to use thelayout manager combined with a builder tool to lay out your GUI. One such builder tool is the NetBeans IDE . Otherwise, if you want to code by hand and do not want to use, thenis recommended as the next most flexible and powerful layout manager.
If you are interested in using JavaFX to create your GUI, see
Working With Layouts in JavaFX.
The
FlowLayout
class provides a very simple layout manager that is used, by default, by the JPanel
objects. The following figure represents a snapshot of an application that uses the flow layout:
Click the Launch button to run FlowLayoutDemo using
Java™ Web Start (download JDK 7 or later). Alternatively, to compile and run the example yourself, consult the example index.
The complete code of this demo is in the
FlowLayoutDemo.java
file.
The FlowLayout
class puts components in a row, sized at their preferred size. If the horizontal space in the container is too small to put all the components in one row, the FlowLayout
class uses multiple rows. If the container is wider than necessary for a row of components, the row is, by default, centered horizontally within the container. To specify that the row is to aligned either to the left or right, use a FlowLayout
constructor that takes an alignment argument. Another constructor of the FlowLayout
class specifies how much vertical or horizontal padding is put around the components.
The code snippet below creates a FlowLayout
object and the components it manages.
FlowLayout experimentLayout = new FlowLayout(); ... compsToExperiment.setLayout(experimentLayout); compsToExperiment.add(new JButton("Button 1")); compsToExperiment.add(new JButton("Button 2")); compsToExperiment.add(new JButton("Button 3")); compsToExperiment.add(new JButton("Long-Named Button 4")); compsToExperiment.add(new JButton("5"));
Select either the Left to Right or Right to Left option and click the Apply orientation button to set up the component’s orientation. The following code snippet applies the Left to Right components orientation to the experimentLayout
.
compsToExperiment.setComponentOrientation( ComponentOrientation.LEFT_TO_RIGHT);
The following table lists constructors of the FlowLayout
class.
Constructor
Purpose
FlowLayout()
Constructs a new FlowLayout
object with a centered alignment and horizontal and vertical gaps with the default size of 5 pixels.
FlowLayout(int align)
Creates a new flow layout manager with the indicated alignment and horizontal and vertical gaps with the default size of 5 pixels. The alignment argument can be FlowLayout.LEADING
, FlowLayout.CENTER
, or FlowLayout.TRAILING
. When the FlowLayout
object controls a container with a left-to right component orientation (the default), the LEADING
value specifies the components to be left-aligned and the TRAILING
value specifies the components to be right-aligned.
FlowLayout (int align, int hgap, int vgap)
Creates a new flow layout manager with the indicated alignment and the indicated horizontal and vertical gaps. The hgap
and vgap
arguments specify the number of pixels to put between components.
The following table lists code examples that use the FlowLayout
class and provides links to related sections.