Calculator problem in android studio

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I’m a beginner and I’m developing a simple calculator in android studio, but it only shows the result of two values, ex: 1+1=2. I would like to do several operations at the same time, e.g. 1+2*3/4

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import static android.R.attr.id;

public class MainActivity extends AppCompatActivity  {

    private double operador1;
    private double operador2;
    private double operadores;

   boolean mAdicao, mSubtacao, mMultiplicacao, mDivisao;

    private EditText txt_visor;


    private Button n1;
    private Button n2;
    private Button n3;
    private Button n4;
    private Button n5;
    private Button n6;
    private Button n7;
    private Button n8;
    private Button n9;
    private Button n0;
    private Button dois_zeros;

    private Button ponto;

    private Button soma;
    private Button subitracao;
    private Button multiplicacao;
    private Button divisao;
    private Button porcento;
    private Button potenciacao;
    private Button raiz;

    private Button igual;

    private Button limpar;

    private Button sair;




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







        txt_visor = (EditText) findViewById(R.id.txt_visor);

        n1 = (Button) findViewById(R.id.n1);
        n2 = (Button) findViewById(R.id.n2);
        n3 = (Button) findViewById(R.id.n3);
        n4 = (Button) findViewById(R.id.n4);
        n5 = (Button) findViewById(R.id.n5);
        n6 = (Button) findViewById(R.id.n6);
        n7 = (Button) findViewById(R.id.n7);
        n8 = (Button) findViewById(R.id.n8);
        n9 = (Button) findViewById(R.id.n9);
        n0 = (Button) findViewById(R.id.n0);
        dois_zeros = (Button) findViewById(R.id.dois_zeros);


        ponto = (Button) findViewById(R.id.ponto);

        soma = (Button) findViewById(R.id.soma);
        subitracao = (Button) findViewById(R.id.subitracao);
        multiplicacao = (Button) findViewById(R.id.multiplicacao);
        divisao = (Button) findViewById(R.id.divisao);
        porcento = (Button) findViewById(R.id.porcento);
        potenciacao = (Button) findViewById(R.id.potenciacao);
        raiz = (Button) findViewById(R.id.raiz);


        igual = (Button) findViewById(R.id.igual);

        limpar = (Button) findViewById(R.id.limpar);


        /* setando o número de cada botão*/

        n1.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "1");
            }
        });


        n2.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "2");
            }
        });

        n3.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "3");
            }
        });

        n4.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "4");
            }
        });

        n5.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "5");
            }
        });

        n6.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "6");
            }
        });

        n7.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "7");
            }
        });

        n8.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "8");
            }
        });

        n9.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "9");
            }
        });

        n0.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "0");
            }
        });

        dois_zeros.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                txt_visor.setText(txt_visor.getText() + "00");
            }
        });

        soma.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {

                if (txt_visor==null){
                    txt_visor.setText("");
                }else {
                    operador1 = Double.parseDouble(txt_visor.getText() + "");
                    mAdicao = true;
                    txt_visor.setText(null);


                }
            }
        });

        subitracao.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {

                if (txt_visor==null){
                    txt_visor.setText("");
                }else {
                    operador1 = Double.parseDouble(txt_visor.getText() + "");
                    mSubtacao = true;
                    txt_visor.setText(null);

                }
            }
        });

        multiplicacao.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {

                if (txt_visor==null){
                    txt_visor.setText("");
                }else {
                    operador1 = Double.parseDouble(txt_visor.getText() + "");
                    mMultiplicacao = true;
                    txt_visor.setText(null);

                }
            }
        });

        divisao.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {

                if (txt_visor==null){
                    txt_visor.setText("");
                }else {
                    operador1 = Double.parseDouble(txt_visor.getText() + "");
                    mDivisao = true;
                    txt_visor.setText(null);

                }
            }
        });

        igual.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {

            operador2 = Double.parseDouble(txt_visor.getText().toString()+"" );

                if (mAdicao==true){

                    txt_visor.setText(operador1 +operador2 +"");


                }
                if (mSubtacao ==true){

                    txt_visor.setText(operador1-operador2+"");
                }
            }
        });



    }
java android calculus
  • 2

    Just accumulate the results in a variable for each change of operation.

  • A tip is to delegate the responsibility for arithmetic operations to a class. This makes it easier to do the treatments and accumulate results in numerical expressions, which is what the calculator does.

  • @diegofm can give an example?

1 answer

3

There are already questions and answers that can help you with this, because there are already libraries able to receive a String like "(2*6)+3" and return the result of the expression.

Maybe the easiest is to use a cited Javascript engine here, who does this.

Behold here some solutions, such as the use of "Beanshell" interpreter, which can be used so:

Interpreter interpreter = new Interpreter();
interpreter.eval("result = (7+21*6)/(32-27)");
System.out.println(interpreter.get("result"));

Behold here how to put Beanshell in Android Studio.

This other post can also help you. See also the use of Mathevaluator quoted here.

  • Thanks for the reply, but it was a prerequisite that I did not use libraries.

  • You can’t even use the "javax.script.Scriptengine" (which you don’t even need to download)?

  • That I do not know friend, but I am very beginner do not know how I use

Browser other questions tagged java android calculus

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