private void updateAnimation(float factor) {
        float initial = mAnimationInitialValue;
        float destination = mReverse ? 0f : 1f;
        mCurrentScale = initial + (destination - initial) * factor;
        mCurColor = blendColors(mStartColor, mEndColor, mCurrentScale);
        computePath(getBounds());
        invalidateSelf();
    }
The two colors that will be used for the seek thumb.

@param startColor Color used for the seek thumb
@param endColor   Color used for popup indicator
caprice/ui/src/main/java/net/qiujuer/genius/ui/drawable/BalloonMarkerDrawable.java