Java Reference
In-Depth Information
The basics of JFrames
As you know from Chap. 1, an instance of class JFrame is a window that can
appear on your monitor (See Fig. 17.1). The window has two visible parts: the
border and the content pane . The border contains the title bar and resize control
(in the lower right corner). The title bar contains the title and the usual maximize,
minimize, and close buttons. The content pane contains GUI components such as
buttons, scrollbars, and text areas —whatever the program has placed on it.
Creating a JFrame
The first statement below declares a variable jf and assigns to it the name
of a new instance of class JFrame , with title "example" . The JFrame window is
initially not visible. The second statement, jf.pack() , tells the JFrame to “lay
out” all the components that have been placed in it. The third statement makes
the window visible. (The JFrame of Fig. 17.1 has no components.)
JFrame jf= new JFrame("example");
jf.setVisible( true );
You can set the size and location of the window. Statement
jf.setSize(200, 70);
changes the window to a width of 200 pixels and a height of 70 pixels.
jf.setLocation(60, 30);
moves the window so that its top left corner is at horizontal pixel 60 and vertical
pixel 30 . To retrieve the current width and height of jf , use function calls:
jf.getWidth() and
To retrieve the position of the top-left corner, use function calls:
jf.getX() and
Figure 17.1:
A JFrame
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