AnimatedLayout part 4: update AnimatedLayout.java

AnimatedLayout.java

...
private int mIdleState = SUMMER_STATE; // set initial state as SUMMER_STATE
...

    public void animateBy(int dy) {
        float newOffset;
        if (dy > 0) {
            newOffset = (mOffsetValue - dy) < 0 ? 0 : mOffsetValue - dy;
        } else {
            //scroll to the left
            newOffset = (mOffsetValue - dy) > getWidth() ? getWidth() : mOffsetValue - dy;
        }

        if (mCurrentAnimation == IDLE_ANIMATION_STATE) {
            //start from idle state
            mCurrentAnimation = (dy < 0) ? FROM_LEFT_TO_RIGHT : FROM_RIGHT_TO_LEFT;

            performScreenShot();
            if (mIdleState == SUMMER_STATE) {
                applyWinter();
            } else {
                applySummer();
            }
        }

        if (newOffset == 0 || newOffset == getWidth()) {
            mIdleState = newOffset == 0 ? WINTER_STATE : SUMMER_STATE;
            if (mIdleState == SUMMER_STATE) {
                applySummer();
            } else {
                applyWinter();
            }
            mCurrentAnimation = IDLE_ANIMATION_STATE;
        }
        updateOffset(newOffset);
        invalidate();
    }

    public boolean isForwardAnimationPossible() {
        return mOffsetValue > 0;
    }

    public boolean isReverseAnimationPossible() {
        return mOffsetValue < getWidth();
    }