private double getInch() {
            DisplayMetrics display = MainActivity.this.getResources().getDisplayMetrics();
            int height = (int) (display.heightPixels / display.ydpi);
            int width = (int) (display.widthPixels / display.xdpi);

            return Math.sqrt((width * width) + (height * height));
        }
        
    int inch = (int)getInch();
 
	private void setTextSize() {
 		if (inch >= 10) { //10-inch
            reserveFieldStoreText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 26);
            reserveFieldDateText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 26);
            reserveFieldTimeText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 26);
        } else if (inch >= 7) { //7-inch
            reserveFieldStoreText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 22);
            reserveFieldDateText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 22);
            reserveFieldTimeText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 22);
        } else {
            reserveFieldStoreText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 14);
            reserveFieldDateText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 14);
            reserveFieldTimeText.setTextSize(TypedValue.COMPLEX_UNIT_SP, 14);
        }
  }