Sum in Textview

Question

I have a Json that returns the values of positive and negative, and that sets the text in mine TextView. This is the calculation I try to do, but it returns a invalid double:

public double num1,num2,resultado;

saldo = (TextView) findViewById(R.id.saldouser);
negativo = (TextView) findViewById(R.id.vendaliv);
positivo = (TextView) findViewById(R.id.compraliv);
date = (TextView) findViewById(R.id.datatrans);

num1 = Double.parseDouble(positivo.getText().toString());
num2 = Double.parseDouble(negativo.getText().toString());
resultado = num1-num2;
System.out.println(resultado);
saldo.setText(resultado);

The mistake is:

Caused by: java.lang.Numberformatexception: Invalid double: ""

Answer 1

Of the two:

1) You use in the text a value like 12,9 or 10,0with comma, as we use in Brazil. But Double uses . as it is used in the US, so he can not interpret that 12,9 is 12.9 and explode.

2) You try to parse an empty string, which is invalid because it does not automatically convert to 0.

Sugestao, use a Try catch block to treat this Exception and/or a function to convert your comma to point if that’s the problem.