How do a simple calculator in Android? How to do it using Buttons and single edit text?

Question

I am learning Android so I want to keep things simple.

I have to add two numbers and display the result in a single editbox. To add with the second number you have stor

Answer 1

//Below having correct programming .
//I did some changes in your code.This code was working nicely try this.
//`import android.os.Bundle;
import android.R.integer;
import android.R.string;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

 public EditText display;  
TextView edt;
Integer c,d,r,b;
String a="0",aa;


Button b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16;

@Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    edt=(EditText)findViewById(R.id.editText1);
    b1=(Button)findViewById(R.id.button1);
    b2=(Button)findViewById(R.id.button2);
    b3=(Button)findViewById(R.id.button3);
    b4=(Button)findViewById(R.id.button4);
    b5=(Button)findViewById(R.id.button5);
    b6=(Button)findViewById(R.id.button6);
    b7=(Button)findViewById(R.id.button7);
    b8=(Button)findViewById(R.id.button8);
    b9=(Button)findViewById(R.id.button9);
    b10=(Button)findViewById(R.id.button0);
    b11=(Button)findViewById(R.id.button11);
    b12=(Button)findViewById(R.id.button12);
    b13=(Button)findViewById(R.id.button13);
    b14=(Button)findViewById(R.id.button14);
    b15=(Button)findViewById(R.id.button15);
    b16=(Button)findViewById(R.id.button16);



    b1.setOnClickListener(new View.OnClickListener() {
         public void onClick(View v) {
             // TODO Auto-generated method stub

             a=edt.getText().toString();
             a=a+"1";
             edt.setText(a);

         }
     });

     b2.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     // TODO Auto-generated method stub

                     a=edt.getText().toString();
                     a=a+"2";
                     edt.setText(a);
                                         }
             });

     b3.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     a=edt.getText().toString();
                     a=a+"3";
                     edt.setText(a);
                                         }
             });


     b4.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     a=edt.getText().toString();
                     a=a+"4";
                     edt.setText(a);

                                         }
             });


     b5.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {

                     a=edt.getText().toString();
                     a=a+"5";
                     edt.setText(a);

                 }
             });


     b6.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     // TODO Auto-generated method stub

                     a=edt.getText().toString();
                     a=a+"6";
                     edt.setText(a);
                                         }
             });


     b7.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {

                     a=edt.getText().toString();
                     a=a+"7";
                     edt.setText(a);
                                         }
             });


     b8.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     // TODO Auto-generated method stub

                     a=edt.getText().toString();
                     a=a+"8";
                     edt.setText(a);

                 }
             });


     b9.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     // TODO Auto-generated method stub

                     a=edt.getText().toString();
                     a=a+"9";
                     edt.setText(a);
                                         }
             });


     b10.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     // TODO Auto-generated method stub

                     a=edt.getText().toString();
                     a=a+"0";
                     edt.setText(a);
                 }
             });


 b11.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {

                       aa=a; 
                       b=1;    
                       a="";
                       edt.setText("+");

                     edt.setText("");
          }
             });





     b12.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {

                     aa=a;
                     b=2;
                     a="";
                     edt.setText("-");
                     edt.setText("");

                 }
             });


     b13.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     aa=a;
                     b=3;
                     a="";
                     edt.setText("*");
                     edt.setText("");

                 }
             });



     b14.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     aa=a;
                     b=4;
                     a="";
                     edt.setText("/");
                     edt.setText("");

                 }
             });


     b15.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {

                     if(b==1){
                       c=Integer.parseInt(aa);

                       d=Integer.parseInt(a);             
                       r=c+d;
                     }
                     else
                     if(b==4){
                         c=Integer.parseInt(aa);
                       d=Integer.parseInt(a);
                       r=c/d; 
                     }else
                         if(b==2){
                             c=Integer.parseInt(aa);
                           d=Integer.parseInt(a);
                           r=c-d; 
                         }
                         else
                             if(b==3){
                                 c=Integer.parseInt(aa);
                               d=Integer.parseInt(a);
                               r=c*d; 
                             }
                     Toast.makeText(MainActivity.this, "Result is::"+r, 10000).show();
                     c=0;
                     b=0;
                     d=0;
                     a="";
                     aa="";
                     edt.setText("");
                 }
             });


     b16.setOnClickListener(new View.OnClickListener()
     {

                 public void onClick(View v) {
                     // TODO Auto-generated method stub

                 edt.setText("");
                 }
             });




 }`