Android Example for addition of two numbers or basic calculator

I have collected all the resources from Internet and also added my own, This blog is only for educational purpose. The program codes are written in java and I will not take any responsibility if it caused any damage to your device. But feel free to contact me via my email. I would like to express my gratitude to all youtube chnnels for creating this blog. 

The following file will be activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"    
android:layout_height="match_parent" 
android:paddingLeft="@dimen/activity_horizontal_margin"    
android:paddingRight="@dimen/activity_horizontal_margin"    
android:paddingTop="@dimen/activity_vertical_margin"    
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"    
android:orientation="vertical"    
android:weightSum="1"    
android:background="#0f0"    >

<EditText        
android:layout_width="336dp"        
android:layout_height="wrap_content"        
android:id="@+id/tfNum1" />
<EditText        
android:layout_width="334dp"        
android:layout_height="wrap_content"        
android:id="@+id/tfNum2" />

<TextView        
android:layout_width="333dp"        
android:layout_height="wrap_content"        
android:textAppearance="?android:attr/textAppearanceLarge"        
android:text="@string/emptystring"        
android:id="@+id/Lresult" />
<LinearLayout        
android:orientation="horizontal"        
android:layout_width="match_parent"        
android:layout_height="wrap_content"        
android:layout_gravity="right"        
android:layout_weight="0.05">    
<Button       
android:layout_width="wrap_content"        
android:layout_height="wrap_content"        
android:text="+"        
android:id="@+id/Badd"        
android:layout_weight="0.05"        
android:onClick="onButtonClick" />
<Button        
android:layout_width="wrap_content"        
android:layout_height="wrap_content"        
android:text=" -"        
android:id="@+id/Bsub"        
android:layout_weight="0.05"        
android:onClick="onButtonClick" />
<Button        
android:layout_width="wrap_content"        
android:layout_height="wrap_content"        
android:text="*"        
android:id="@+id/Bmul"        
android:layout_weight="0.05"        
android:onClick="onButtonClick" />

<Button        
android:layout_width="wrap_content"        
android:layout_height="wrap_content"        
android:text="/"        
android:id="@+id/Bdiv"        
android:layout_weight="0.05"        
android:onClick="onButtonClick" />    
</LinearLayout>
</LinearLayout>




The Java file below is named as MainActivity.java
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {

Double num1,num2,ans;
Boolean flag;    
@Override    
protected void onCreate(Bundle savedInstanceState) 
{
        super.onCreate(savedInstanceState);        
setContentView(R.layout.activity_main);   
 }

public void onButtonClick(View v)
{

EditText a1=(EditText)  findViewById(R.id.tfNum1);        
EditText a2=(EditText)  findViewById(R.id.tfNum2);
TextView tv=(TextView) findViewById(R.id.Lresult);
num1=Double.parseDouble(a1.getText().toString());        
num2=Double.parseDouble(a1.getText().toString());
if (v.getId()==R.id.Badd)
            ans=num1+num2;        
if (v.getId()==R.id.Bsub)
            ans=num1-num2;        
if (v.getId()==R.id.Bmul)
            ans=num1*num2;        
if(v.getId()==R.id.Bdiv)
            if(num2==0)
                flag=true;            
else                
ans=num1/num2;
tv.setText(ans+"");   
 }
}