TurnLayoutManager.java 文件源码

/**
 * Accounting for the settings of {@link Gravity} and {@link Orientation}, find the center point
 * around which this layout manager should arrange list items.  Place the resulting coordinates
 * into {@code out}, to avoid reallocation.
 */
private Point deriveCenter(@Gravity int gravity,
                           int orientation,
                           @Dimension int radius,
                           @Dimension int peekDistance,
                           Point out) {
    final int gravitySign = gravity == Gravity.START ? -1 : 1;
    final int distanceMultiplier = gravity == Gravity.START ? 0 : 1;
    int x, y;
    switch (orientation) {
        case Orientation.HORIZONTAL:
            y = (distanceMultiplier * getHeight()) + gravitySign * (Math.abs(radius - peekDistance));
            x = getWidth() / 2;
            break;
        case Orientation.VERTICAL:
        default:
            y = getHeight() / 2;
            x = (distanceMultiplier * getWidth()) + gravitySign * (Math.abs(radius - peekDistance));
            break;
    }
    out.set(x, y);
    return out;
}