Code in android studio closes before finishing

Question

The code in android studio closes before finishing. I’m a beginner, so I don’t know where the problem is, but the program must be to multiply one value entered by the percentage of another chosen. The chosen one is in Radio and the inserted in text.

package com.example.djalmacunha.aulatwo;

import android.app.Activity;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.RadioGroup;


public class MainActivity extends Activity {

    //declaracao de todas as variaveis
    private RadioGroup porc;
    private RadioButton op1, op2, op3;
    private Button vai;
    private EditText put;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //colocando os ID's referentes a cada coisa
        porc = (RadioGroup) findViewById(R.id.radioGroup);
        vai = (Button) findViewById(R.id.button);
        put = (EditText) findViewById(R.id.insere);
        op1 = (RadioButton) findViewById(R.id.quarenta);
        op2 = (RadioButton) findViewById(R.id.quarentaCinco);
        op3 = (RadioButton) findViewById(R.id.cinquenta);

        //para executar quando apertar o botao
        vai.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //checa o valor digitado e o valor no radio
                double var1 = Double.parseDouble(put.getText().toString());
                double var2 = 0;
                boolean checked = ((RadioButton) v).isChecked();
                switch(v.getId()) {
                    case R.id.quarenta:
                        if (checked)
                            var2 = 1.40;
                            break;
                    case R.id.quarentaCinco:
                        if (checked)
                            var2 = 1.45;
                        break;
                    case R.id.cinquenta:
                        if (checked)
                            var2 = 1.50;
                            break;
                }

                //faz a conta
                double resp = var1 * var2;
                AlertDialog.Builder alerta = new AlertDialog.Builder(MainActivity.this);
                alerta.setTitle("Resultado");

                //imprime a resposta
                alerta.setMessage("O resultado é " + resp);
                alerta.setNeutralButton("OK", null);
                alerta.show();
            }

        });
    }
}