RTEditor/src/main/java/com/onegravity/rteditor/utils/Helper.java
public static boolean isRTL(CharSequence s, int start, int end) {
        if (s == null || s.length() == 0) {
            // empty string --> determine the direction from the default language
            return isRTL(Locale.getDefault());
        }

        if (start == end) {
            // if no character is selected we need to expand the selection
            start = Math.max(0, --start);
            if (start == end) {
                end = Math.min(s.length(), ++end);
            }
        }

        try {
            Bidi bidi = new Bidi(s.subSequence(start, end).toString(), Bidi.DIRECTION_DEFAULT_LEFT_TO_RIGHT);
            return ! bidi.baseIsLeftToRight();
        }
        catch (IndexOutOfBoundsException e) {
            return false;
        }
    }
public static boolean isRTL(CharSequence s, int start, int end) {
        if (s == null || s.length() == 0) {
            // empty string --> determine the direction from the default language
            return isRTL(Locale.getDefault());
        }

        if (start == end) {
            // if no character is selected we need to expand the selection
            start = Math.max(0, --start);
            if (start == end) {
                end = Math.min(s.length(), ++end);
            }
        }

        try {
            Bidi bidi = new Bidi(s.subSequence(start, end).toString(), Bidi.DIRECTION_DEFAULT_LEFT_TO_RIGHT);
            return ! bidi.baseIsLeftToRight();
        }
        catch (IndexOutOfBoundsException e) {
            return false;
        }
    }
public static boolean isRTL ( CharSequence s , int start , int end ) { if ( s == null || s . length ( ) == 0 ) { // empty string --> determine the direction from the default language return isRTL ( Locale . getDefault ( ) ) ; } if ( start == end ) { // if no character is selected we need to expand the selection start = Math . max ( 0 , -- start ) ; if ( start == end ) { end = Math . min ( s . length ( ) , ++ end ) ; } } try { Bidi bidi = new Bidi ( s . subSequence ( start , end ) . toString ( ) , Bidi . DIRECTION_DEFAULT_LEFT_TO_RIGHT ) ; return ! bidi . baseIsLeftToRight ( ) ; } catch ( IndexOutOfBoundsException e ) { return false ; } }
This method determines if the direction of a substring is right-to-left.
If the string is empty that determination is based on the default system language
Locale.getDefault().
The method can handle invalid substring definitions (start > end etc.), in which case the
method returns False.

@return True if the text direction is right-to-left, false otherwise.
This method determines if the direction of a substring is right - to - left . If the string is empty that determination is based on the default system language Locale . getDefault () . The method can handle invalid substring definitions ( start > end etc . ) in which case the method returns False .