Basic calculator with details of the resolution of the operations, for example, you know that 2 + 2/2 = 3, because if we are not alert we could assume that the result is 2, this calculator will show you the order of the operations that are performing, In this case first make the division 2/2 = 1 and then the sum 2 + 1 = 3, it will leave a detail as follows:

2/2 = 1.0
2 + 1.0 = 3.0
2 + 2/2 = 3.0

In this way you can audit the resolution of more complex operations involving square roots, exponents, grouping signs, etc. And have a clear idea of how the calculator came to that result.

If you press a few seconds you can copy the detail to the clipboard and paste it in a text message or another part to send it to your friends.

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-- For developers
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* .- You can invoke the calculator from any Android application and pass a formula:

String formula = "175.26*16%";
Intent intentCalculadora = new Intent(Intent.ACTION_VIEW);
ComponentName componentName = new ComponentName("com.rb.calculadorae", "com.rb.calculadorae.CalcActivity");
intentCalculadora.setComponent(componentName);
intentCalculadora.putExtra("formula", formula );
startActivityForResult(intentCalculadora, RESULTADO_CALCULADORA);

* - and the result can be recovered:

if (requestCode == RESULTADO_CALCULADORA){
if (resultCode == RESULT_OK){
String resultado = data.getStringExtra("resultado");
if (resultado != null && !resultado.isEmpty()){
txtFormula.setText(resultado);
}
}
}