The easiest way would be to parse the expression string in the textView control. There are some primitiv algorithm available. See http://en.wikipedia.org/wiki/Shunting-yard_algorithm

does it show 3 ?

if yes , i think it occures because you actually just add latest pressed digits (btn_val1,2,3) and not all of pressed digits . coz of that when u type 11+22 it adds 1+2.

if it is the problem we can say that this program only adds one digit numbers and for other numbers just adds their last digits . so maybe if we change some lines like following it will work :

btn_val1 += btn1.getText().toString();

textview .append("1");

btn_val2 += btn2.getText().toString();

textview .append("2");

btn_val3 += btn3.getText().toString();

textview .append("3"); and so on 

1. In your XML file, there is no component with id = editText1. I'm not sure that your User Interface can work properly.

2. Your code will never work like You want because

public void btn1Click(View view){

  btn1 = (Button) findViewById(R.id.btn1);

  btn_val1 = btn1.getText().toString();

  textview = (TextView) findViewById(R.id.textView2);

  textview.append(btn_val1);

}

this is one case in Your code btn_val1 value will always = 1 because this code btn_val1 = btn1.getText().toString(); same with btn2 and btn3.

for the solution I agree with Mr. Morteza Taghipour

3. in function public void btnEq(View view)

I'm not sure that btnAdd value can be null, I think btnAdd will always not null, You'd better change btnAdd to Your btn_valAdd and then check the value isNullorEmpty or have string value.

at the End You Should reset your variable value if you want make it reusable.

Hope that can help You.

Good Luck.

Hi. I am not an android expert, but I tried some experiments. I suggest you to do the following thing:

1. create 2 textviews for input values, 1 button for add operation and a label for result of the computation

2. simplify your main class to get the contents from testViews and add them and show the result in the label

3. if this works, begin to build more complex examples, by using buttons for each digit and so on.

Br,

Claudiu

Dear Nitish,

Here is a complete working code that I have written just for you I hope it helps you, and feel free to contact me if you need more help:

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/** Author @Kelechi C Ofoleta*/

package com.kogonuso.calculator;

import android.os.Bundle;

import android.support.v7.app.ActionBarActivity;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class Main extends ActionBarActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Button b = (Button)findViewById(R.id.button1);

b.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

EditText n1 = (EditText)findViewById(R.id.editText1);

EditText n2 = (EditText)findViewById(R.id.editText2);

TextView msg = (TextView)findViewById(R.id.msg);

try{

if((n1.getText().equals("")) || (n2.getText().equals(""))){

return;

}else{

double a = Double.valueOf(n1.getText().toString()).doubleValue();

double b = Double.parseDouble(n2.getText().toString());

double result = a+b;

msg.setText(result+"");

}

}catch(Exception e){

Toast bread = Toast.makeText(Main.this, "You must enter numbers to continue",Toast.LENGTH_LONG);

bread.show();

}

}

});

}

}

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Calculator

Hello world!

Settings

Number 1:

Number 2:

Calc

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http://www.kogonuso.com/