| 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",
TL means "items top-to-bottom, lines left-to-right", 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.
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