Using Input Methods on the Java
Platform
by Naoto Sato
Do you know how many characters are defined in
Unicode Standard 3.0
, the supported version in the Java 2
runtime environment? It is 49,194! You may wonder how these characters
are input into an application written for the Java platform. There are input
methods for this purpose. Input methods allow the user to input text where
each character may not be directly represented by a single keystroke. A
user may compose text in advance from a series of keystrokes and insert the
final desired text into the document when the composition is complete. In
the Java 2 development environment, we provide the
Input Method Framework
for the collaboration between text components and input methods. By using
this framework, Swing text components can handle the input method composition
on-the-spot, or inline; in other words, the text being composed
is immediately visually and logically inserted into the text backing store.
Swing text components accomplish this on-the-spot editing style using the
client API
in the Input Method Framework. The
engine SPI
in the Input Method Framework allows you to plug your favorite input methods
into any Java runtime environment. Like other Java technology-based applications,
an input method can be deployed on any platform where the Java runtime environment
is available. Furthermore, unlike applications, you can enjoy a common user
interface across platforms; a feature that platform-native input methods
seldom provide.
In this article, you will learn how to use input methods in
your Swing text components. The information in this article is based on
the Java 2 runtime environment, version 1.4.0 or higher, and the operating
systems listed in the
Supported Locales
document.
Here is the table of contents of this article:
Installing Input Methods
To install an input method is pretty easy. An input method
is provided in JAR archive form, and you need only to place it in the
extension directory. This is usually lib/ext, but you can
also specify the extension directory at runtime by setting the
java.ext.dirs system property. We provide a sample input method
named City Input Method, available
here
, to use in this article. Copy the CityIM.jar file to the
extension directory and the installation is done!
Selecting Input Methods
Once an input method is installed in the extension directory,
you will notice an extra menu item in the System menu on Solaris
TM or Microsoft Windows when you run an application which uses
the Swing text component, as shown here:
After selecting Select Input Method, the following popup appears:
This menu contains a list of all input methods available in this
runtime environment. Input methods that are provided by the underlying operating
system are listed in the System Input Methods submenu. Input methods
listed below the separator line are Java technology-based input methods.
In this example, City Input Method demonstrates that it can support
multiple languages. The specific languages supported are displayed as submenu
items.
If you set the user locale to Japanese, you would see Japanese
menu items if translations are provided by the input methods.
Using Input Methods
To use an input method, select it in the popup menu. Let's select
City Input Method in the Japanese locale; this menu item is highlighted
in the previous picture. A small popup window appears at the bottom-right
corner of the screen. This tells you that City Input Method - Japanese
is now selected.
Now, type s, f, and o from the keyboard.
You would see sfo with (dotted) underline, which means that
sfo is still in composition mode. This type of editing is often known
as pre-composing. Since City Input Method is an input method
to input city names from airport codes, such as SFO, you can see candidate
city names in some languages by pressing the space bar, as shown here:
Once you determine the candidate you prefer, commit that
pre-composed string into the text backing store. This is typically done
by pressing the Return key. In the example, it looks like
this:
Input Method Selection by a Hot Key
For platforms that do not have the Select Input Method menu
item in the system menu (e.g. Linux), we provide an alternative way to select
an input method by pressing a user-defined hot key. This way of selecting
an input method is also useful for platforms that have the menu item in the
system menu, e.g., Solaris and Microsoft Windows. If you press the hot key,
the same popup menu discussed previously is displayed.
To define a hot key combination, download the Input Method
Hot Key tool by clicking the button below.
and run it as follows:
java -jar InputMethodHotKey.jar [-system]
This pops up a window like this:
After you set up your favorite hot key, press that combination on
any Swing text component. You will see the same popup menu for selecting
an input method. For multi-user platforms, the -system option
is provided. If you set a hot key with the -system option,
that hot key is active for all users.
Other Sample Input Methods
We've seen how the City Input Method works in the Swing
text component. We also provide the following useful, but unsupported, input
methods:
Code Point Input Method
The Code Point Input Method is a simple input method
that allows Unicode characters to be entered via their hexadecimal code
point values. A user enters the hexadecimal code point value using the
\uxxxx notation for character literals.
In general, the input method passes characters through unchanged. However,
when the user types a \, the input method enters composition
mode. In composition mode, the user types the desired code point using
the \uxxxx notation, where x is one of the set
[0-9a-fA-F]. When a valid sequence is entered it is converted to
the corresponding Unicode character and committed. The input method then
returns to pass-through mode until another \ character is entered.
While in composition mode, the user can use the left arrow, right arrow,
backspace and delete keys to edit the sequence. The \u characters
can only be deleted if there are no hex digits present in the composition
sequence. Deleting the \u returns the input method to pass-through
mode.
Since the \ character triggers composition mode to begin,
a user must type two \ characters in order for a single
\ to be added to the text. When a single \ has been
entered, if the next character is not a u, both the \
and the subsequent character are committed and the input method returns
to pass-through mode.
The Code Point Input Method can be downloaded by clicking the
button below.
Indic Input Method
This input method archive contains several writing
scripts used in India. Other than Devanagari, which is the supported writing
system in Java 2 runtime edition, version 1.4, it also contains the input
methods for the following writing scripts: Bengali, Gujarati, Gurmukhi,
Kannada, Malayalam, Oriya, Tamil, and Telugu. This input method basically
maps the US 101/104 keyboard layout to the INSCRIPT layouts used in these
writing scripts. Here are the diagrams
for each keyboard layout, and the mapping
table
from the Latin alphabet to each writing script.
You can download the Indic input method by clicking the button below.
Thai Input Method
This input method implements the input-sequence checking
for Thai, as defined in the Thai API Consortium's "WTT" Input/Output
Methods document. This input method also maps the US 101/104 keyboard
layout to the
Thai TIS820-2538 layout
. Here is the mapping table
from the Latin alphabet to the Thai writing script.
The Thai input method is available by clicking the button below.
Further Information
For further information on using the Input Method Framework, see the documentation
here
. Also, you may find this
Java internationalization forum
useful.
Finally, you can send
feedback
to the Java Internationalization team.
|
|
Print-friendly Version
