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Java Look-and-Feel Design Guidelines – Part IV. Eileen Kraemer University of Georgia CSCI 4800/600. Previously, we talked about …. Applet v. Application Placement of applets Designing for accessibility Checking for accessibility Usability testing Internationalization / localization

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java look and feel design guidelines part iv

Java Look-and-Feel Design Guidelines – Part IV

Eileen Kraemer

University of Georgia

CSCI 4800/600

previously we talked about
Previously, we talked about …
  • Applet v. Application
  • Placement of applets
  • Designing for accessibility
  • Checking for accessibility
  • Usability testing
  • Internationalization / localization
  • Creating/using resource bundles
designing for accessibility
Designing for accessibility
  • Provide accessible names, accessible descriptions
  • Use mnemonics and keyboard shortcuts
  • All interface components must be keyboard traversable
    • Assign initial keyboard focus
    • Specify tab traversal order
  • Don’t customize fonts or colors unnecessarily
  • If necessary, use properties to specify colors, fonts
  • Use dynamic GUI layout
  • Custom components must implement accessible
slide4
Now, …
  • … let’s look at the “nuts and bolts” of accomplishing these goals
the java accessibility api jaapi
The Java Accessibility API (JAAPI)
  • standard extension in all releases of the Java 2 platform
  • component can utilize this extension by implementing the Accessible interface
    • only one method call: getAccessibleContext()
    • returns an instance of AccessibleContext
      • specific to the component
      • provides the info and functionality to enable accessibility
  • AccessibleContext
    • info about the component's role (button, checkbox, etc.)
    • accessible name (more on this soon)
    • Number of children, & more
    • Can generate accessibility events when a noteworthy event has occurred.
  • All of the standard JFC/Swing components implement the Accessible interface
accessible name description how used
Accessible name, description: how used
  • accessible name
    • succinct explanation of component’s purpose
    • assistive technology will often present (speak) the name of each component encountered by a user
  • accessible description
    • more verbose explanation
    • provide in cases where additional info needed
    • assistive tech retrieves when user requests it
accessible name how to set
Accessible name: how to set
  • JFC/Swing components with non-editable text (menu items, buttons, etc.) have accessible name set automatically
  • Other components need to have accessible name set by developer
  • If the component has a label:

JTextField text = new JTextField(20);

JLabel label = new Label("Address Line 1");

label.setLabelFor(text);

// ... Add the text and label to a Container

  • For ImageIcons , create using:

ImageIcon(URL url, String name);

accessible description how to set
Accessible description: how to set
  • Accessible descriptions set automatically by setting tooltiptext:

JComponent.setTooltipText( )

  • If component has no label or tooltip, directly set name & description:
    • permanently overrides values pulled from label or tooltip

AccessibleContext context = component.getAccessibleContext(); context.setAccessibleName("Zip"); context.setAccessibleDescription("Recipient's Zip Code");

don t customize fonts or colors unnecessarily
Don’t Customize Fonts or Colors Unnecessarily
  • JFC/Swing components/ applications automatically inherit font and color properties from desktop and user prefs.
  • In most cases, get good results by accepting user's preferences.  
but if you have to specify colors and fonts
But, if you have to specify colors and fonts ….
  • Use a properties file
  • Example:
    • want flight simulator to have a red "stop" button in Western countries
    • define a property,
    • store it in a file, flightsim.properties:

flightsim.stop.color=#ff0000

then use the properties
Then, use the properties:
  • The program can load properties file as a ResourceBundle:

ResourceBundle resources = null;

Color stopColor = Color.red; // the default

try {

resources=ResourceBundle.getBundle("flightsim");

String colorString = resources.getString("flightsim.stop.color");

stopColor = Color.decode(colorString); // the specified

}

catch (MissingResourceException missingException)

{

// Report the error, according to severity

} // stopColor has now been customized

use dynamic gui layout
Use Dynamic GUI Layout
  • Don’t call setSize() with constant values.
    • defeats dynamic layout
    • resulting application won’t adapt properly to users' settings.
  • Instead, adjust the size of each JFrame, JDialog, and JWindow at creation and each time its contents change

window.setSize(window.getPreferredSize());

    • allows all nested layout managers to affect the size and position of each object at runtime.
    • If component’s preferred size is not acceptable(rare), call setSize() with a value between getMinimumSize() and getMaximumSize().
dynamic layoutmanagers
Dynamic LayoutManagers
  • position graphical objects relative to each other
    • changes in size are handled automatically
    • components never obscure one another.
  • All JFC/Swing layout managers are dynamic (BorderLayout, FlowLayout, GridBagLayout, etc.)

setLayout(null); // Don’t do this!!

    • Requires manually setting (x,y) of every component.
    • interface won’t work right with many accessibility options, internationalization , user-defined preferences.
custom layout managers
Custom Layout Managers
  • Implement LayoutManager2 interface
    • (old LayoutManager interface is obsolete).
    • Components should be positioned relative to each other when the toolkit invokes layoutContainer() on the custom layout manager.
all interface components must be keyboard traversable
All Interface Components Must Be Keyboard Traversable
  • … because many people can’t use a pointing device effectively
  • Pressing tab key should move input focus from component to component
  • shift-tab should move focus in opposite direction.
how to implement
How to implement?
  • default FocusManager sets focus order : left-to-right and top-to-bottom.
  • If component shouldn’t receive input focus, create a subclass and override isFocusTraversable() to return false.
  • Invoke setNextFocusableComponent() on each JComponent to "hard-wire" the focus traversal order.
    • Messy to do this on some components and have others use the default ordering. If used, invoke on all JComponents in a window.
  • Implement a subclass of java.awt.FocusManager and install it with the static method FocusManager.setCurrentManager().
use mnemonics
Use Mnemonics
  • Mnemonics
    • underlined characters that appear in menu items and on the buttons in some dialog boxes.
    • can only be activated when the item is visible and does not require a modifier key (e.g., the user does not need to press the Alt key).
    • If keyboard use is to be practical, then All menu items must have mnemonics

menu = new JMenu();

menu.setText(resources.getString("fileMenu.label"));

menu.setMnemonic( resources.getString("fileMenu.mnemonic").charAt(0));

item = new JMenuItem();

item.setMnemonic( resources.getString("menuitem.file.new.mnemonic").charAt(0));

use accelerators
Use Accelerators
  • displayed on menu items or buttons in parentheses after the item's text [e.g., "Save (Ctrl+S)"].
  • requires the use of a modifier key
  • can be activated any time the application's window has the input focus.

item = new JMenuItem(); item.setAccelerator(KeyStroke.getKeyStroke( resources.getString("menuitem.file.new.accelerator")));

custom components must implement accessible
Custom Components Must Implement Accessible
  • All standard JComponent subclasses implement this interface and do everything necessary to be accessible
  • All custom components should extend a standard class as far down the JFC/Swing inheritance hierarchy as possible.
    • For example, you want round buttons
      • First try to extend JButton, override all paint methods, add support for any new properties.
      • If JButton is too restrictive, then try to extend JButton's superclass, AbstractButton.
      • Only if AbstractButton is too restrictive should you extend directly from JComponent.
  • JComponent doesn’t implement Accessible, so subclass must do more work to work w/ assistive technologies.
    • Some methods do exist in JComponent to help: getAccessibleParent() and getAccessibleName() will work properly for most JComponent subclasses, with no additional code (other than 'implements Accessible').
custom components continued
Custom components, continued
  • must express its accessible role as specifically as possible. See: http://java.sun.com/j2se/1.4.2/docs/api/javax/accessibility/AccessibleContext.html
  • Each JFC/Swing class contains a protected inner class that actually does the accessibility work, and the root class is JComponent.AccessibleJComponent
    • To extend accessibility behavior of subclass, create a protected inner class that extends the inner class of the superclass
    • override getAccessibleContext() to create an instance of this new accessibility class.
example
Example

public class WarningLight extends JComponent

implements Accessible {

public AccessibleContext getAccessibleContext() {

// variable accessibleContext is protected in superclass

if (accessibleContext == null) {

accessibleContext = new AccessibleWarningLight();

}

return accessibleContext;

}

protected class AccessibleWarningLight extends AccessibleJComponent {

public AccessibleRole getAccessibleRole() {

return AccessibleRole.ALERT;

}

… // Implementation of WarningLight omitted...

}

test cases
Test Cases
  • 1. Don't touch your mouse
    • Bring up each window and popup in your application and attempt to visit every component using only the Tab key on the keyboard.
    • Use the application without touching the mouse
    • Verify that:
      • Application’s features are all available
      • Frequently-used functionality is directly accessible via an accelerator
      • All menu items have mnemonics  
test cases23
Test Cases
  • 2. Change the default font and color
    • Choose a font of 24 points or larger, and colors other than the default.
    • Bring up each window of the application and verify that screen objects do not overlap and that the colors are correct.
    • If overlapping occurs, check the code that interacts with the LayoutManager in that window.  
test cases24
Test Cases
  • Try using a low-vision look-and-feel
  • Here’s a sample LowVisionMetalLookAndFeel.java
  • Compile the file
  • Add this code to your application:

import LowVisionMetalLookAndFeel; // ... code omitted

try { UIManager.setLookAndFeel("LowVisionMetalLookAndFeel");

}

catch (Exception ex) {

System.out.println("Failed loading Low Vision Metal

Look and Feel");

ex.printStackTrace(System.out);

}

test cases25
Test Cases
  • 3. Use a screen reader
    • Download and install a trial version of a screen reader that works with Java applications, (more/better links coming soon)
      • http://cap.ic.gc.ca/english/learning.html
  • Bring up each window in your application and tab to every component, verifying that you hear a reasonable description of each component as it receives the input focus.
  • Turn your display off.
    • Try to use your application in this mode, accessing both core functionality and more lightly-used features.
internationalization
Internationalization
  • Identify Culturally Dependent Data
  • Isolate Translatable Text in Resource Bundles
  • Deal with Compound Messages
  • Format Dates and Times
  • Use Unicode Character Properties
  • Compare Strings Properly
  • Convert Non-Unicode Text
nuts and bolts
Nuts and Bolts …
  • Creating and accessing resource bundles …
  • ResourceBundle objects contain locale-specific objects.
  • When you need a locale-specific object, you fetch it from a ResourceBundle, which returns the object that matches the end user's Locale.
the resourcebundle class
The ResourceBundle Class
  • each ResourceBundle is a set of related subclasses that share the same base name.
  • Example:

ButtonLabel // base_name

ButtonLabel_de // with language code

ButtonLabel_en_GB // with language and country codes

ButtonLabel_fr_CA_UNIX // with lang, country, and variant codes

to select a resourcebundle
To select a ResourceBundle
  • invoke the ResourceBundle.getBundle method.
  • Example:

Locale currentLocale = new Locale("fr", "CA", "UNIX"); ResourceBundle introLabels = ResourceBundle.getBundle(“ButtonLabel”, currentLocale);