android.support.v4.view.ViewCompat#LAYOUT_DIRECTION_LTR源码实例Demo

/**
 * Replaces a movement direction with its relative version by taking layout direction into
 * account.
 *
 * @param flags           The flag value that include any number of movement flags.
 * @param layoutDirection The layout direction of the View. Can be obtained from
 *                        {@link ViewCompat#getLayoutDirection(android.view.View)}.
 * @return Updated flags which uses relative flags ({@link #START}, {@link #END}) instead
 * of {@link #LEFT}, {@link #RIGHT}.
 * @see #convertToAbsoluteDirection(int, int)
 */
public static int convertToRelativeDirection(int flags, int layoutDirection) {
    int masked = flags & ABS_HORIZONTAL_DIR_FLAGS;
    if (masked == 0) {
        return flags; // does not have any abs flags, good.
    }
    flags &= ~masked; //remove left / right.
    if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
        // no change. just OR with 2 bits shifted mask and return
        flags |= masked << 2; // START is 2 bits after LEFT, END is 2 bits after RIGHT.
        return flags;
    } else {
        // add RIGHT flag as START
        flags |= ((masked << 1) & ~ABS_HORIZONTAL_DIR_FLAGS);
        // first clean RIGHT bit then add LEFT flag as END
        flags |= ((masked << 1) & ABS_HORIZONTAL_DIR_FLAGS) << 2;
    }
    return flags;
}
 

public static int convertToRelativeDirection(int flags, int layoutDirection) {
    int masked = flags & ABS_HORIZONTAL_DIR_FLAGS;
    if (masked == 0) {
        return flags;// does not have any abs flags, good.
    }
    flags &= ~masked; //remove left / right.
    if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
        // no change. just OR with 2 bits shifted mask and return
        flags |= masked << 2; // START is 2 bits after LEFT, END is 2 bits after RIGHT.
        return flags;
    } else {
        // add RIGHT flag as START
        flags |= ((masked << 1) & ~ABS_HORIZONTAL_DIR_FLAGS);
        // first clean RIGHT bit then add LEFT flag as END
        flags |= ((masked << 1) & ABS_HORIZONTAL_DIR_FLAGS) << 2;
    }
    return flags;
}
 

public int convertToAbsoluteDirection(int flags, int layoutDirection) {
    int masked = flags & RELATIVE_DIR_FLAGS;
    if (masked == 0) {
        return flags;// does not have any relative flags, good.
    }
    flags &= ~masked; //remove start / end
    if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
        // no change. just OR with 2 bits shifted mask and return
        flags |= masked >> 2; // START is 2 bits after LEFT, END is 2 bits after RIGHT.
        return flags;
    } else {
        // add START flag as RIGHT
        flags |= ((masked >> 1) & ~RELATIVE_DIR_FLAGS);
        // first clean start bit then add END flag as LEFT
        flags |= ((masked >> 1) & RELATIVE_DIR_FLAGS) >> 2;
    }
    return flags;
}
 

/**
 * Replaces a movement direction with its relative version by taking layout direction into
 * account.
 *
 * @param flags           The flag value that include any number of movement flags.
 * @param layoutDirection The layout direction of the View. Can be obtained from
 *                        {@link ViewCompat#getLayoutDirection(android.view.View)}.
 * @return Updated flags which uses relative flags ({@link #START}, {@link #END}) instead
 * of {@link #LEFT}, {@link #RIGHT}.
 * @see #convertToAbsoluteDirection(int, int)
 */
public static int convertToRelativeDirection(int flags, int layoutDirection) {
    int masked = flags & ABS_HORIZONTAL_DIR_FLAGS;
    if (masked == 0) {
        return flags; // does not have any abs flags, good.
    }
    flags &= ~masked; //remove left / right.
    if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
        // no change. just OR with 2 bits shifted mask and return
        flags |= masked << 2; // START is 2 bits after LEFT, END is 2 bits after RIGHT.
        return flags;
    } else {
        // add RIGHT flag as START
        flags |= ((masked << 1) & ~ABS_HORIZONTAL_DIR_FLAGS);
        // first clean RIGHT bit then add LEFT flag as END
        flags |= ((masked << 1) & ABS_HORIZONTAL_DIR_FLAGS) << 2;
    }
    return flags;
}
 

@Override
public void onRtlPropertiesChanged(int layoutDirection) {
    super.onRtlPropertiesChanged(layoutDirection);
    int viewCompatLayoutDirection = layoutDirection == View.LAYOUT_DIRECTION_RTL ?
            ViewCompat.LAYOUT_DIRECTION_RTL :
            ViewCompat.LAYOUT_DIRECTION_LTR;
    if (viewCompatLayoutDirection != mLayoutDirection) {
        PagerAdapter adapter = super.getAdapter();
        int position = 0;
        if (adapter != null) {
            position = getCurrentItem();
        }
        mLayoutDirection = viewCompatLayoutDirection;
        if (adapter != null) {
            adapter.notifyDataSetChanged();
            setCurrentItem(position);
        }
    }
}
 

private Drawable resolveLeftShadow() {
    int layoutDirection = ViewCompat.getLayoutDirection(this);
    // Prefer shadows defined with start/end gravity over left and right.
    if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
        if (mShadowStart != null) {
            // Correct drawable layout direction, if needed.
            mirror(mShadowStart, layoutDirection);
            return mShadowStart;
        }
    } else {
        if (mShadowEnd != null) {
            // Correct drawable layout direction, if needed.
            mirror(mShadowEnd, layoutDirection);
            return mShadowEnd;
        }
    }
    return mShadowLeft;
}
 

private Drawable resolveRightShadow() {
    int layoutDirection = ViewCompat.getLayoutDirection(this);
    if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
        if (mShadowEnd != null) {
            // Correct drawable layout direction, if needed.
            mirror(mShadowEnd, layoutDirection);
            return mShadowEnd;
        }
    } else {
        if (mShadowStart != null) {
            // Correct drawable layout direction, if needed.
            mirror(mShadowStart, layoutDirection);
            return mShadowStart;
        }
    }
    return mShadowRight;
}
 

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    Resources r = context.getResources();
    int horizontalPadding = (int) r.getDimension(R.dimen.category_preview__app_list__padding__horizontal);
    int horizontalPaddingFirst = (int) r.getDimension(
            R.dimen.category_preview__app_list__padding__horizontal__first);
    int horizontalPaddingLast = (int) r.getDimension(
            R.dimen.category_preview__app_list__padding__horizontal__last);
    boolean isLtr = ViewCompat.getLayoutDirection(parent) == ViewCompat.LAYOUT_DIRECTION_LTR;
    int itemPosition = parent.getChildLayoutPosition(view);
    boolean first = itemPosition == 0;
    boolean end = itemPosition == categoryItemCount - 1;

    // Leave this "paddingEnd" local variable here for clarity when converting from
    // left/right to start/end for RTL friendly layout.
    // noinspection UnnecessaryLocalVariable
    int paddingEnd = end ? horizontalPaddingLast : horizontalPadding;
    int paddingStart = first ? horizontalPaddingFirst : horizontalPadding;

    int paddingLeft = isLtr ? paddingStart : paddingEnd;
    int paddingRight = isLtr ? paddingEnd : paddingStart;
    outRect.set(paddingLeft, 0, paddingRight, 0);
}
 

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    int position = parent.getChildAdapterPosition(view);
    Resources resources = context.getResources();
    int horizontalPadding = (int) resources.getDimension(R.dimen.whats_new__padding__app_card__horizontal);
    int verticalPadding = (int) resources.getDimension(R.dimen.whats_new__padding__app_card__vertical);

    int relativePositionInCycle = position % 5;
    if (position == 0) {
        outRect.set(horizontalPadding, verticalPadding, horizontalPadding, verticalPadding);
    } else if (relativePositionInCycle != 0) {
        // The item on the left will have both left and right padding. The item on the right
        // will only have padding on the right. This will allow the same amount of padding
        // on the left, centre, and right of the grid, rather than double the padding in the
        // middle (which would happen if both left and right padding was set for both items).
        boolean isLtr = ViewCompat.getLayoutDirection(parent) == ViewCompat.LAYOUT_DIRECTION_LTR;
        boolean isAtStart = relativePositionInCycle == 1 || relativePositionInCycle == 3;
        int paddingStart = isAtStart ? horizontalPadding : 0;
        int paddingLeft = isLtr ? paddingStart : horizontalPadding;
        int paddingRight = isLtr ? horizontalPadding : paddingStart;
        outRect.set(paddingLeft, 0, paddingRight, verticalPadding);
    } else {
        outRect.set(horizontalPadding, 0, horizontalPadding, verticalPadding);
    }
}
 

/**
 * Show a toast message with the hex color code below the view.
 */
public void showHint() {
    final int[] screenPos = new int[2];
    final Rect displayFrame = new Rect();
    getLocationOnScreen(screenPos);
    getWindowVisibleDisplayFrame(displayFrame);
    final Context context = getContext();
    final int width = getWidth();
    final int height = getHeight();
    final int midy = screenPos[1] + height / 2;
    int referenceX = screenPos[0] + width / 2;
    if (ViewCompat.getLayoutDirection(this) == ViewCompat.LAYOUT_DIRECTION_LTR) {
        final int screenWidth = context.getResources().getDisplayMetrics().widthPixels;
        referenceX = screenWidth - referenceX; // mirror
    }
    StringBuilder hint = new StringBuilder("#");
    if (Color.alpha(color) != 255) {
        hint.append(Integer.toHexString(color).toUpperCase(Locale.ENGLISH));
    } else {
        hint.append(String.format("%06X", 0xFFFFFF & color).toUpperCase(Locale.ENGLISH));
    }
    Toast cheatSheet = Toast.makeText(context, hint.toString(), Toast.LENGTH_SHORT);
    if (midy < displayFrame.height()) {
        // Show along the top; follow action buttons
        cheatSheet.setGravity(Gravity.TOP | GravityCompat.END, referenceX,
                screenPos[1] + height - displayFrame.top);
    } else {
        // Show along the bottom center
        cheatSheet.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL, 0, height);
    }
    cheatSheet.show();
}
 

/**
 * Return the layout direction for a given Locale
 *
 * @param locale the Locale for which we want the layout direction. Can be null.
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
public static int getLayoutDirectionFromLocale(Locale locale) {
    if (locale != null && !locale.equals(ROOT)) {
        final String scriptSubtag = ICUCompat.getScript(
                ICUCompat.addLikelySubtags(locale.toString()));
        if (scriptSubtag == null) return getLayoutDirectionFromFirstChar(locale);

        if (scriptSubtag.equalsIgnoreCase(ARAB_SCRIPT_SUBTAG) ||
                scriptSubtag.equalsIgnoreCase(HEBR_SCRIPT_SUBTAG)) {
            return ViewCompat.LAYOUT_DIRECTION_RTL;
        }
    }

    return ViewCompat.LAYOUT_DIRECTION_LTR;
}
 

/**
 * Return the layout direction for a given Locale
 *
 * @param locale the Locale for which we want the layout direction. Can be null.
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
public static int getLayoutDirectionFromLocale(Locale locale) {
    if (locale != null && !locale.equals(ROOT)) {
        final String scriptSubtag = ICUCompat.getScript(
                ICUCompat.addLikelySubtags(locale.toString()));
        if (scriptSubtag == null) return getLayoutDirectionFromFirstChar(locale);

        if (scriptSubtag.equalsIgnoreCase(ARAB_SCRIPT_SUBTAG) ||
                scriptSubtag.equalsIgnoreCase(HEBR_SCRIPT_SUBTAG)) {
            return ViewCompat.LAYOUT_DIRECTION_RTL;
        }
    }

    return ViewCompat.LAYOUT_DIRECTION_LTR;
}
 

/**
 * Return the layout direction for a given Locale
 *
 * @param locale the Locale for which we want the layout direction. Can be null.
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
public static int getLayoutDirectionFromLocale(Locale locale) {
    if (locale != null && !locale.equals(ROOT)) {
        final String scriptSubtag = ICUCompat.getScript(
                ICUCompat.addLikelySubtags(locale.toString()));
        if (scriptSubtag == null) return getLayoutDirectionFromFirstChar(locale);

        if (scriptSubtag.equalsIgnoreCase(ARAB_SCRIPT_SUBTAG) ||
                scriptSubtag.equalsIgnoreCase(HEBR_SCRIPT_SUBTAG)) {
            return ViewCompat.LAYOUT_DIRECTION_RTL;
        }
    }

    return ViewCompat.LAYOUT_DIRECTION_LTR;
}
 

/**
 * Return the layout direction for a given Locale
 *
 * @param locale the Locale for which we want the layout direction. Can be null.
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
public static int getLayoutDirectionFromLocale(@Nullable Locale locale) {
    if (locale != null && !locale.equals(ROOT)) {
        final String scriptSubtag = ICUCompat.getScript(
                ICUCompat.addLikelySubtags(locale.toString()));
        if (scriptSubtag == null) return getLayoutDirectionFromFirstChar(locale);

        if (scriptSubtag.equalsIgnoreCase(ARAB_SCRIPT_SUBTAG) ||
                scriptSubtag.equalsIgnoreCase(HEBR_SCRIPT_SUBTAG)) {
            return ViewCompat.LAYOUT_DIRECTION_RTL;
        }
    }

    return ViewCompat.LAYOUT_DIRECTION_LTR;
}
 

/**
 * Return the layout direction for a given Locale
 *
 * @param locale the Locale for which we want the layout direction. Can be null.
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
public static int getLayoutDirectionFromLocale(Locale locale) {
    if (locale != null && !locale.equals(ROOT)) {
        final String scriptSubtag = ICUCompat.getScript(
                ICUCompat.addLikelySubtags(locale.toString()));
        if (scriptSubtag == null) return getLayoutDirectionFromFirstChar(locale);

        if (scriptSubtag.equalsIgnoreCase(ARAB_SCRIPT_SUBTAG) ||
                scriptSubtag.equalsIgnoreCase(HEBR_SCRIPT_SUBTAG)) {
            return ViewCompat.LAYOUT_DIRECTION_RTL;
        }
    }

    return ViewCompat.LAYOUT_DIRECTION_LTR;
}
 

/**
 * Check the lock mode of the drawer with the given gravity.
 *
 * @param edgeGravity Gravity of the drawer to check
 * @return one of {@link #LOCK_MODE_UNLOCKED}, {@link #LOCK_MODE_LOCKED_CLOSED} or
 *         {@link #LOCK_MODE_LOCKED_OPEN}.
 */
@LockMode
public int getDrawerLockMode(@EdgeGravity int edgeGravity) {
    int layoutDirection = ViewCompat.getLayoutDirection(this);

    switch (edgeGravity) {
        case Gravity.LEFT:
            if (mLockModeLeft != LOCK_MODE_UNDEFINED) {
                return mLockModeLeft;
            }
            int leftLockMode = (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) ?
                    mLockModeStart : mLockModeEnd;
            if (leftLockMode != LOCK_MODE_UNDEFINED) {
                return leftLockMode;
            }
            break;
        case Gravity.RIGHT:
            if (mLockModeRight != LOCK_MODE_UNDEFINED) {
                return mLockModeRight;
            }
            int rightLockMode = (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) ?
                    mLockModeEnd : mLockModeStart;
            if (rightLockMode != LOCK_MODE_UNDEFINED) {
                return rightLockMode;
            }
            break;
        case GravityCompat.START:
            if (mLockModeStart != LOCK_MODE_UNDEFINED) {
                return mLockModeStart;
            }
            int startLockMode = (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) ?
                    mLockModeLeft : mLockModeRight;
            if (startLockMode != LOCK_MODE_UNDEFINED) {
                return startLockMode;
            }
            break;
        case GravityCompat.END:
            if (mLockModeEnd != LOCK_MODE_UNDEFINED) {
                return mLockModeEnd;
            }
            int endLockMode = (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) ?
                    mLockModeRight : mLockModeLeft;
            if (endLockMode != LOCK_MODE_UNDEFINED) {
                return endLockMode;
            }
            break;
    }

    return LOCK_MODE_UNLOCKED;
}
 

/**
 * Fallback algorithm to detect the locale direction. Rely on the fist char of the
 * localized locale name. This will not work if the localized locale name is in English
 * (this is the case for ICU 4.4 and "Urdu" script)
 *
 * @param locale
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
private static int getLayoutDirectionFromFirstChar(Locale locale) {
    switch(Character.getDirectionality(locale.getDisplayName(locale).charAt(0))) {
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT:
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC:
            return ViewCompat.LAYOUT_DIRECTION_RTL;

        case Character.DIRECTIONALITY_LEFT_TO_RIGHT:
        default:
            return ViewCompat.LAYOUT_DIRECTION_LTR;
    }
}
 

/**
 * Fallback algorithm to detect the locale direction. Rely on the fist char of the
 * localized locale name. This will not work if the localized locale name is in English
 * (this is the case for ICU 4.4 and "Urdu" script)
 *
 * @param locale
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
private static int getLayoutDirectionFromFirstChar(Locale locale) {
    switch(Character.getDirectionality(locale.getDisplayName(locale).charAt(0))) {
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT:
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC:
            return ViewCompat.LAYOUT_DIRECTION_RTL;

        case Character.DIRECTIONALITY_LEFT_TO_RIGHT:
        default:
            return ViewCompat.LAYOUT_DIRECTION_LTR;
    }
}
 

/**
 * Fallback algorithm to detect the locale direction. Rely on the fist char of the
 * localized locale name. This will not work if the localized locale name is in English
 * (this is the case for ICU 4.4 and "Urdu" script)
 *
 * @param locale
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
private static int getLayoutDirectionFromFirstChar(Locale locale) {
    switch(Character.getDirectionality(locale.getDisplayName(locale).charAt(0))) {
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT:
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC:
            return ViewCompat.LAYOUT_DIRECTION_RTL;

        case Character.DIRECTIONALITY_LEFT_TO_RIGHT:
        default:
            return ViewCompat.LAYOUT_DIRECTION_LTR;
    }
}
 

/**
 * Fallback algorithm to detect the locale direction. Rely on the fist char of the
 * localized locale name. This will not work if the localized locale name is in English
 * (this is the case for ICU 4.4 and "Urdu" script)
 *
 * @param locale
 * @return the layout direction. This may be one of:
 * {@link ViewCompat#LAYOUT_DIRECTION_LTR} or
 * {@link ViewCompat#LAYOUT_DIRECTION_RTL}.
 *
 * Be careful: this code will need to be updated when vertical scripts will be supported
 */
private static int getLayoutDirectionFromFirstChar(Locale locale) {
    switch(Character.getDirectionality(locale.getDisplayName(locale).charAt(0))) {
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT:
        case Character.DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC:
            return ViewCompat.LAYOUT_DIRECTION_RTL;

        case Character.DIRECTIONALITY_LEFT_TO_RIGHT:
        default:
            return ViewCompat.LAYOUT_DIRECTION_LTR;
    }
}