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ComponentOrientation.javaAPI DocJava SE 5 API6203Fri Aug 26 14:56:44 BST 2005java.awt

ComponentOrientation

public final class ComponentOrientation extends Object implements Serializable
The ComponentOrientation class encapsulates the language-sensitive orientation that is to be used to order the elements of a component or of text. It is used to reflect the differences in this ordering between Western alphabets, Middle Eastern (such as Hebrew), and Far Eastern (such as Japanese).

Fundamentally, this governs items (such as characters) which are laid out in lines, with the lines then laid out in a block. This also applies to items in a widget: for example, in a check box where the box is positioned relative to the text.

There are four different orientations used in modern languages as in the following table.

LT RT TL TR
A B C C B A A D G G D A
D E F F E D B E H H E B
G H I I H G C F I I F C

(In the header, the two-letter abbreviation represents the item direction in the first letter, and the line direction in the second. For example, LT means "items left-to-right, lines top-to-bottom", BL means "items bottom-to-top, lines bottom-to-top", and so on.)

The orientations are:

  • LT - Western Europe (optional for Japanese, Chinese, Korean)
  • RT - Middle East (Arabic, Hebrew)
  • TR - Japanese, Chinese, Korean
  • TL - Mongolian
Components whose view and controller code depends on orientation should use the isLeftToRight() and isHorizontal() methods to determine their behavior. They should not include switch-like code that keys off of the constants, such as: 
if (orientation == LEFT_TO_RIGHT) {
...
} else if (orientation == RIGHT_TO_LEFT) {
...
} else {
// Oops
}
This is unsafe, since more constants may be added in the future and since it is not guaranteed that orientation objects will be unique.

Fields Summary
private static final int
UNK_BIT
private static final int
HORIZ_BIT
private static final int
LTR_BIT
public static final ComponentOrientation
LEFT_TO_RIGHT
Items run left to right and lines flow top to bottom Examples: English, French.
public static final ComponentOrientation
RIGHT_TO_LEFT
Items run right to left and lines flow top to bottom Examples: Arabic, Hebrew.
public static final ComponentOrientation
UNKNOWN
Indicates that a component's orientation has not been set. To preserve the behavior of existing applications, isLeftToRight will return true for this value.
private int
orientation
Constructors Summary
private ComponentOrientation(int value)

        orientation = value;
Methods Summary
public static java.awt.ComponentOrientationgetOrientation(java.util.Locale locale)
Returns the orientation that is appropriate for the given locale.

param
locale the specified locale

        // A more flexible implementation would consult a ResourceBundle
        // to find the appropriate orientation.  Until pluggable locales
        // are introduced however, the flexiblity isn't really needed.
        // So we choose efficiency instead.
        String lang = locale.getLanguage();
        if( "iw".equals(lang) || "ar".equals(lang) 
            || "fa".equals(lang) || "ur".equals(lang) ) 
        {
            return RIGHT_TO_LEFT;
        } else {
            return LEFT_TO_RIGHT;
        }
public static java.awt.ComponentOrientationgetOrientation(java.util.ResourceBundle bdl)
Returns the orientation appropriate for the given ResourceBundle's localization. Three approaches are tried, in the following order:
  1. Retrieve a ComponentOrientation object from the ResourceBundle using the string "Orientation" as the key.
  2. Use the ResourceBundle.getLocale to determine the bundle's locale, then return the orientation for that locale.
  3. Return the default locale's orientation.

deprecated
As of J2SE 1.4, use {@link #getOrientation(java.util.Locale)}.

        ComponentOrientation result = null;

        try {
            result = (ComponentOrientation)bdl.getObject("Orientation");
        }
        catch (Exception e) {
        }

        if (result == null) {
            result = getOrientation(bdl.getLocale());
        }
        if (result == null) {
            result = getOrientation(Locale.getDefault());
        }
        return result;
public booleanisHorizontal()
Are lines horizontal? This will return true for horizontal, left-to-right writing systems such as Roman.


                        
       
        return (orientation & HORIZ_BIT) != 0;
public booleanisLeftToRight()
HorizontalLines: Do items run left-to-right?
Vertical Lines: Do lines run left-to-right?
This will return true for horizontal, left-to-right writing systems such as Roman.

        return (orientation & LTR_BIT) != 0;