onMeasure.java

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

	final int width = getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec);
	final int height = getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec);
	final int min = Math.min(width, height);

	mTranslateX = (int) (width * 0.5f);
	mTranslateY = (int) (height * 0.5f);

	int arcDiameter = min - getPaddingLeft();
	mArcRadius = arcDiameter / 2;
	float top = height / 2 - (arcDiameter / 2);
	float left = width / 2 - (arcDiameter / 2);
	mArcRect.set(left, top, left + arcDiameter, top + arcDiameter);

	updateIndicatorIconPosition();
	super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}