问题描述
I am learning Java gui. The way I learnt to create a window is to inherit or Extend JFrame
class and it is good to use it, as JFrame
contains all the properties of a Window. Now If I want to add something to this window, I need to use add()
method. But Today I came across JPanel
which also creates a windows and we can add stuff by jpanelObjec.add()
.
What is the difference between the two methods? Are they somehow related?
You should not extend the JFrame
class unnecessarily (only if you are adding extra functionality to the JFrame
class)
JFrame:
JFrame
extends Component
and Container
.
It is a top level container used to represent the minimum requirements for a window. This includes Border
s, resizability (is the JFrame
resizeable?), title bar, controls (minimize/maximize allowed?), and event handlers for various Event
s like windowClose
, windowOpened
etc.
JPanel:
JPanel
extends Component
, Container
and JComponent
It is a generic class used to group other Component
s together.
It is useful when working with
LayoutManager
s e.g.GridLayout
f.i adding components to differentJPanel
s which will then be added to theJFrame
to create the gui. It will be more manageable in terms ofLayout
and re-usability.It is also useful for when painting/drawing in Swing, you would override
paintComponent(..)
and of course have the full joys of double buffering.
A Swing GUI cannot exist without a top level container like (JWindow
, Window
, JFrame
Frame
or Applet
), while it may exist without JPanel
s.
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