Swing JPanel and JFrame

Swing is an extension library to the AWT, includes new and improved components that enhance the look and functionality of GUIs. Swing can be used to build Standalone swing gui Apps as well as Servlets and Applets. It employs a model/view design architecture. Swing is more portable and more flexible than AWT.

Swing is another GUI toolkit which is used to add more interactivity in java programmes. In this section we will discuss about Swing with an example and we will have a look at different features of Swing in comparison with AWT.

JPanel and JFrame

We know that Swing contains several components. In this chapter and all the subsequent chapters in this section we will see how we can use these components with examples.

JPanel
JPanel is Swing’s version of the AWT class Panel and uses the same default layout, FlowLayout. JPanel is descended directly from JComponent.

JFrame
Java Swing Tutorial Explaining the JFrame class. The components added to the frame are referred to as its contents; these are managed by the contentPane. To add a component to a JFrame, we must use its contentPane instead.JFrame is a Window with border, title and buttons. When JFrame is set visible, an event dispatching thread is started. JFrame objects store several objects including a Container object known as the content pane. To add a component to a JFrame, add it to the content pane.

JFrame Features
It’s a window with title, border, (optional) menu bar and user-specified components.
It can be moved, resized, iconified. It is not a subclass of JComponent.
Delegates responsibility of managing user-specified components to a content pane, an instance of JPanel.

Centering JFrame
By default, a Jframe is displayed in the upper-left corner of the screen. To display a frame at a specified location, you can use the setLocation(x, y) method in the JFrame class. This method places the upper-left corner of a frame at location (x, y).

The Swing API keeps improving with abstractions such as the setDefaultCloseOperation method for the JFrame

Crating a JFrame Window

Step 1: Construct an object of the JFrame class.
Step 2: Set the size of the Jframe.
Step 3: Set the title of the Jframe to appear in the title bar (title bar will be blank if no title is set).
Step 4: Set the default close operation. When the user clicks the close button, the program stops running.
Step 5: Make the Jframe visible.

How to position JFrame on Screen?

frame.setLocationRelativeTo( null );

Java JFrame Hierarchy
javax.swing
Class JFrame
java.lang.Object
java.awt.Component
java.awt.Container
java.awt.Window
java.awt.Frame
javax.swing.JFrame

All Implemented Interfaces:
Accessible, ImageObserver, MenuContainer, RootPaneContainer, Serializable, WindowConstants

JFrame Constructor
JFrame()
Constructs a new frame that is initially invisible.

JFrame(GraphicsConfiguration gc)
Creates a Frame in the specified GraphicsConfiguration of a screen device and a blank title.

JFrame(String title)
Creates a new, initially invisible Frame with the specified title.

JFrame(String title, GraphicsConfiguration gc)
Creates a JFrame with the specified title and the specified GraphicsConfiguration of a screen device.