The 'X' method could not be found in the 'Z' activity

When I run my code I get an alert that the program stopped. The code is about a motorcycle rental app. That I have to calculate the rental price per day:

public class MainActivity extends Activity {

    private RadioButton radio0,radio1,radio2,radio3,radio4;
    private CheckBox CheckBox1,CheckBox2;
    private TextView tv4;
    private EditText et2;
    private double precioinicial;
    private double preciofinal;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        radio0=(RadioButton)findViewById(R.id.radio0);
        radio1=(RadioButton)findViewById(R.id.radio1);
        radio2=(RadioButton)findViewById(R.id.radio2);
        radio3=(RadioButton)findViewById(R.id.radio3);
        radio4=(RadioButton)findViewById(R.id.radio4);

        CheckBox1=(CheckBox)findViewById(R.id.CheckBox1);
        CheckBox2=(CheckBox)findViewById(R.id.CheckBox2);
        et2=(EditText)findViewById(R.id.et2);   //CANTIDAD DIAS DE ALQUILAR 
        tv4=(TextView)findViewById(R.id.tv4);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    public void importe (View v){
        String CantidadDias= et2.getText().toString();
        int cd=Integer.parseInt(CantidadDias);  // CANTIDAD DE DIAS EN VARIABLE TIPO INT
        precioinicial=0;
        preciofinal=0;
        if (radio0.isChecked()) {  //custom
                precioinicial=20;
            }
        else if (radio1.isChecked()) {   //scooter
                precioinicial=10;
        }
        else if (radio2.isChecked()) {    //crooss
                precioinicial=15;
        }

        /*if (CheckBox1.isChecked()==true) {   //con seguro 20% mas por dia.
            for (int i=0; i<cd; i++){
                double por = (20*precioinicial) / 100 ;
                precioinicial = precioinicial + por;
            }
        }
        if (CheckBox2.isChecked()==true) {      //con casco 1USD por dia
            for (int z=0; z<cd; z++){
                precioinicial = precioinicial + 1;
            }

        }*/

        if (radio3.isChecked()) {      //contado
            double porcentaje= (10*precioinicial) /100;
            precioinicial = precioinicial - porcentaje;
        }



        preciofinal=precioinicial;
        tv4.setText("Importe: " + preciofinal);

    }

}

I do not know where the error may be.