Frame by frame #3

SpinnerLoaderView.java

private float calculateArcSize(float animationProgress) {
    final double adjustedProgress = Math.sin(animationProgress * Math.PI);
    // ARC_MAX_DEGREES is the maximum size the arc will have in degrees.
    // ARC_MAX_DEGREES = 180 means that at it's largest it will cover
    // half the circle.
    return (float) adjustedProgress * -ARC_MAX_DEGREES;
}

private float calculateArcStart(float animationProgress) {
    final float deceleratedProgress = mDecelerateInterpolator.getInterpolation(animationProgress);
    // ARC_START_OFFSET_DEGREES is used to offset the starting position,
    // -90 makes the top of the view the starting point.
    return ARC_START_OFFSET_DEGREES + deceleratedProgress * DEGREES_IN_CIRCLE;
}