Advanced Java Class GUI part 1 Intro to GUI GUI = Graphical User - - PowerPoint PPT Presentation

Advanced Java Class

GUI – part 1

Intro to GUI

• GUI = Graphical User Interface -- “Gooey”
• Just because it’s “gooey” does not mean you may

write messy code.

– GUI is the “view layer”, and it should be separated from the controller and model layers.

• AWT = Abstract Windowing Toolkit
• Swing = better versions of AWT classes

GUI terminology

• Components = buttons, text fields, frames, dialog boxes,

scrollbars, popup menus, scrollable lists, etc.

• Containers = things that hold Components. A container is also

a component. Examples: Panel, Window.

• LayoutManagers arrange Components inside of Containers.
• Use Graphics objects to draw directly onto a component. This

can draw shapes, text, images, etc.

• “Painting” is when a component is drawn onto the screen.
• Events occur when a user clicks the mouse, types on the

keyboard, types in a text field, or selects an item from a list.

• Listeners (or adapters) handle events, and are specific to a

certain type of event.

A few important GUI packages

• AWT (java.awt and subpackages)

– AWT Events (java.awt.event) – Java2D (java.awt.geom)

• Swing (javax.swing and subpackages)

– Swing Events (javax.swing.event)

Swing vs. AWT

• Don’t mix AWT with Swing, and always use Swing if available
• AWT was original GUI API – quite limited!

– not very platform independent – you must do double-buffering yourself – native windows consume a lot of system resources

• Swing is built on AWT, and is a big improvement

– mostly light-weight classes – 100% pure java = platform independent, because it doesn’t depend on native code – pluggable look and feel allows the program to reflect the platform it’s currently running on – double buffers automatically

• Note that Swing components start with “J”.

– “Frame” refers to the old AWT class. – “JFrame” refers to the new Swing class.

Swing Components

• common swing components: see figure 6-

3, p 393-396

• MVC layers

– The model layer is a separate class, which may be shared by multiple Swing components – The Controller and View layers of a component are not separated, because of the nature of GUI components – the view is the controller! – See figure 6-4 on page 397 & 398

Layout Managers

• LayoutManagers arrange components

within Containers.

• They account for things that you cannot

know at compile time, like differing screen resolutions, platform differences, fonts, etc.

• Containers are components, and child

containers can have a LayoutManger that is different from their parent’s.

Using LayoutManagers

• Create a new Container. It has a default

LayoutManager, which you can override by calling the setLayout method on it.

• LayoutManager classes:

– BorderLayout – BoxLayout – CardLayout – FlowLayout – GridBagLayout – GridLayout

Layout Paradigms

• BorderLayout: North, South, East, West, and Center. figures 6-12

& 6-13

• FlowLayout: lines the components up horizontally from left to right.

Can specifiy justification; default is center. fig. 6-14

• GridLayout: has columns and rows. components are added left to

right and top to bottom, like a text editor. figure 6-15

• GridbagLayout: more flexible than GridLayout – components can

be added to any cell, and can span multiple rows and columns. figure 6-16

• CardLayout: imagine a deck of cards – only one component is

visible at a time.

• BoxLayout: components are in a single-file line, which can be

horizontal or vertical. figure 6-17

• Note: the above figures are in a JTabbedPane, which does it’s own

LayoutManaging.

Painting

• You can override a Swing component’s

paintComponent method if you don’t want to use the component’s default appearance. Call super.paintComponent (unless you want transparency).

• Call repaint() when you want to explicitly refresh

what the user is seeing.

• You can also override update() if you want close

control over the refreshing of a part of the component’s appearance.

Methods you can paint with

• Graphics class

– drawString – drawLine – drawRect – drawPolygon – drawArc – drawImage – fillRect – fillPolygon – fillArc

• Graphics class,

continued...

– setColor – setFont – setXORMode( Color c)

• gives colors that are an

XOR of c and what was already there – fun to play with

– setPaintMode()

• just overwrite what’s there

– this is the default

Java 2D

• Parts of API

– Graphics2D class in java.awt – java.awt.geom – java.awt.font – java.awt.image

• Advantages over Graphics class

– antialiasing smooths edges – can fill with contents other than a solid color – can use any system font – printing is easier (see chapter 7) – can paint any shape you want, not just predefined ones – “Strokes” – any width, and varying patterns (dashed, etc.) – can squish, stretch, rotate, etc. anything you draw