public void evaluate(String expr, EvaluateCallback callback) {
    expr = mTokenizer.getNormalizedExpression(expr);
    // remove any trailing operators
    while (expr.length() > 0 && "+-/*".indexOf(expr.charAt(expr.length() - 1)) != -1) {
      expr = expr.substring(0, expr.length() - 1);
    }
    /*try {
      if (expr.length() == 0 || Double.valueOf(expr) != null) {
        callback.onEvaluate(expr, null, Calculator.INVALID_RES_ID);
        return;
      }
    } catch (NumberFormatException e) {
      // expr is not a simple number
    }*/
    if (expr.length() == 0) {
    callback.onEvaluate(expr, null, Calculator.INVALID_RES_ID);
    return;
    }
    try {
     /*************代值的代码在这里**********/
      double result = mSymbols.eval(expr);
      if (Double.isNaN(result)) {
        callback.onEvaluate(expr, null, R.string.error_nan);
      } else {
        /* The arity library uses floating point arithmetic when evaluating the expression
        leading to precision errors in the result. The method doubleToString hides these
         errors; rounding the result by dropping N digits of precision.*/
        final String resultString = mTokenizer.getLocalizedExpression(
            Util.doubleToString(result, MAX_DIGITS, ROUNDING_DIGITS));
        callback.onEvaluate(expr, resultString, Calculator.INVALID_RES_ID);
      }
    } catch (SyntaxException e) {
      callback.onEvaluate(expr, null, R.string.error_syntax);
    }
}

public void evaluate(String expr, EvaluateCallback callback) {
    expr = mTokenizer.getNormalizedExpression(expr);
    // remove any trailing operators
    while (expr.length() > 0 && "+-/*".indexOf(expr.charAt(expr.length() - 1)) != -1) {
      expr = expr.substring(0, expr.length() - 1);
    }
    /*try {
      if (expr.length() == 0 || Double.valueOf(expr) != null) {
        callback.onEvaluate(expr, null, Calculator.INVALID_RES_ID);
        return;
      }
    } catch (NumberFormatException e) {
      // expr is not a simple number
    }*/
    if (expr.length() == 0) {
    callback.onEvaluate(expr, null, Calculator.INVALID_RES_ID);
    return;
    }
    try {
      /**************   添加的过滤代码  ***********/
      expr=expr.replaceAll("(?<=(sin|cos|tan)[(])(?!pi)","pi/180*");
      double result = mSymbols.eval(expr);
      if (Double.isNaN(result)) {
        callback.onEvaluate(expr, null, R.string.error_nan);
      } else {
        /* The arity library uses floating point arithmetic when evaluating the expression
         leading to precision errors in the result. The method doubleToString hides these
         errors; rounding the result by dropping N digits of precision.*/
        final String resultString = mTokenizer.getLocalizedExpression(
            Util.doubleToString(result, MAX_DIGITS, ROUNDING_DIGITS));
        callback.onEvaluate(expr, resultString, Calculator.INVALID_RES_ID);
      }
    } catch (SyntaxException e) {
      callback.onEvaluate(expr, null, R.string.error_syntax);
    }
}