private void drawGuideLine(@NonNull Canvas canvas){
  float offset=(float)(mRadius / Math.sqrt(2));
  float topLeftPointX=mCenterPointX - offset;
  float topLeftPointY=mCenterPointY - offset;
  float topRightPointX=mCenterPointX + offset;
  float bottomLeftPointY=mCenterPointY + offset;
  canvas.drawLine(topLeftPointX,topLeftPointY,topRightPointX,topLeftPointY,mGuideLinePaint);
  canvas.drawLine(mCenterPointX - mRadius,mCenterPointY,mCenterPointX + mRadius,mCenterPointY,mGuideLinePaint);
  canvas.drawLine(topLeftPointX,bottomLeftPointY,topRightPointX,bottomLeftPointY,mGuideLinePaint);
  canvas.drawLine(topLeftPointX,topLeftPointY,topLeftPointX,bottomLeftPointY,mGuideLinePaint);
  canvas.drawLine(mCenterPointX,mCenterPointY - mRadius,mCenterPointX,mCenterPointY + mRadius,mGuideLinePaint);
  canvas.drawLine(topRightPointX,topLeftPointY,topRightPointX,bottomLeftPointY,mGuideLinePaint);
}

private void drawGuideLine ( @ NonNull Canvas canvas ) { float offset = ( float ) ( mRadius / Math . sqrt ( 2 ) ) ; float topLeftPointX = mCenterPointX - offset ; float topLeftPointY = mCenterPointY - offset ; float topRightPointX = mCenterPointX + offset ; float bottomLeftPointY = mCenterPointY + offset ; canvas . drawLine ( topLeftPointX , topLeftPointY , topRightPointX , topLeftPointY , mGuideLinePaint ) ; canvas . drawLine ( mCenterPointX - mRadius , mCenterPointY , mCenterPointX + mRadius , mCenterPointY , mGuideLinePaint ) ; canvas . drawLine ( topLeftPointX , bottomLeftPointY , topRightPointX , bottomLeftPointY , mGuideLinePaint ) ; canvas . drawLine ( topLeftPointX , topLeftPointY , topLeftPointX , bottomLeftPointY , mGuideLinePaint ) ; canvas . drawLine ( mCenterPointX , mCenterPointY - mRadius , mCenterPointX , mCenterPointY + mRadius , mGuideLinePaint ) ; canvas . drawLine ( topRightPointX , topLeftPointY , topRightPointX , bottomLeftPointY , mGuideLinePaint ) ; }
draw a guideline on canvas
