Android Simple Calculator

Simple Calculator example..
I created a simple calculator  Android application to understand basic functions in Android.
 
CalculatorActivity.java

package codesstore.calculator;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class CalculatorActivity extends Activity implements OnClickListener {
    Button buttonPlus;
    Button buttonMinus;
    Button buttonDivide;
    Button buttonMultiply;
    Button buttonOk;
    TextView textAnswer;
    TextView textOperator;
    EditText num1;
    EditText num2;
    double sum;

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

        buttonMinus = (Button) findViewById(R.id.buttonMinus);
        buttonPlus = (Button) findViewById(R.id.buttonPlus);
        buttonDivide = (Button) findViewById(R.id.buttonDivide);
        buttonMultiply = (Button) findViewById(R.id.buttonMultiply);
        buttonOk = (Button) findViewById(R.id.buttonOk);
        num1 = (EditText) findViewById(R.id.num1);
        num2 = (EditText) findViewById(R.id.num2);
        textAnswer = (TextView) findViewById(R.id.textAnswer);
        textOperator = (TextView) findViewById(R.id.textOperator);
        
        buttonOk.setOnClickListener(this);
        buttonPlus.setOnClickListener(this);
        buttonMinus.setOnClickListener(this);
        buttonMultiply.setOnClickListener(this);
        buttonDivide.setOnClickListener(this);

    }

    @Override
    public void onClick(View src) {

        switch (src.getId()) {
        case R.id.buttonOk:
            textAnswer.setText(String.valueOf(sum));
            break;
        case R.id.buttonPlus:
            sum = Double.parseDouble(String.valueOf(num1.getText()))
                    + Double.parseDouble(String.valueOf(num2.getText()));
            textOperator.setText("+");
            break;
        case R.id.buttonMinus:
            sum = Double.parseDouble(String.valueOf(num1.getText()))
                    - Double.parseDouble(String.valueOf(num2.getText()));
            textOperator.setText("-");
            break;
        case R.id.buttonMultiply:
            sum = Double.parseDouble(String.valueOf(num1.getText()))
                    * Double.parseDouble(String.valueOf(num2.getText()));
            textOperator.setText("*");
            break;
        case R.id.buttonDivide:
            sum = Double.parseDouble(String.valueOf(num1.getText()))
                    / Double.parseDouble(String.valueOf(num2.getText()));
            textOperator.setText("/");
            break;
        }

    }
}

main.xml
Main xml is used to create user interface.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/title" android:gravity="center" android:textSize="30dp" android:paddingTop="3dp" android:paddingBottom="10dp"/>


    <LinearLayout
        android:id="@+id/inputs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >


        <EditText
            android:id="@+id/num1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1" />



        <TextView
            android:id="@+id/textOperator"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1" android:gravity="center" android:textSize="25dp"/>



        <EditText
            android:id="@+id/num2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1" >

            <requestFocus />
        </EditText>

    </LinearLayout>


    <LinearLayout
        android:id="@+id/answerbox"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >



        <TextView
            android:id="@+id/textAnswer"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:layout_weight="1" android:textSize="25dp"/>

    </LinearLayout>


    <LinearLayout
        android:id="@+id/buttons"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/buttonPlus"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+" android:layout_weight="1"/>


        <Button
            android:id="@+id/buttonMinus"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="-" android:layout_weight="1"/>


        <Button
            android:id="@+id/buttonDivide"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="/" android:layout_weight="1"/>


        <Button
            android:id="@+id/buttonMultiply"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="*" android:layout_weight="1"/>


        <Button
            android:id="@+id/buttonOk"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="=" android:layout_weight="1"/>

    </LinearLayout>

</LinearLayout>v 

strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="title">Simple Calculator</string>
    <string name="app_name">Calculator</string>

</resources>

R.java
This is a file auto generated by android.

/* AUTO-GENERATED FILE.  DO NOT MODIFY.
 *
 * This class was automatically generated by the
 * aapt tool from the resource data it found.  It
 * should not be modified by hand.
 */

package codesstore.calculator;

public final class R {
    public static final class attr {
    }
    public static final class drawable {
        public static final int calculator_icon=0x7f020000;
        public static final int ic_launcher=0x7f020001;
    }
    public static final class id {
        public static final int answerbox=0x7f050004;
        public static final int buttonDivide=0x7f050009;
        public static final int buttonMinus=0x7f050008;
        public static final int buttonMultiply=0x7f05000a;
        public static final int buttonOk=0x7f05000b;
        public static final int buttonPlus=0x7f050007;
        public static final int buttons=0x7f050006;
        public static final int inputs=0x7f050000;
        public static final int num1=0x7f050001;
        public static final int num2=0x7f050003;
        public static final int textAnswer=0x7f050005;
        public static final int textOperator=0x7f050002;
    }
    public static final class layout {
        public static final int main=0x7f030000;
    }
    public static final class string {
        public static final int app_name=0x7f040001;
        public static final int title=0x7f040000;
    }
}

Project structure in eclipse

 outline window