Simple Android Application for Native Calculator

Aim:

To develop a Simple Android Application for Native Calculator.

Procedure:

Creating a New project:

Open Android Stdio and then click on File -> New -> New project.

Then type the Application name as “ex.no.3″ and click Next.

Then select the Minimum SDK as shown below and click Next.

Then select the Empty Activity and click Next.

Finally click Finish.

It will take some time to build and load the project.
After completion it will look as given below.

Designing layout for the Android Application:

Click on app -> res -> layout -> activity_main.xml.

Now click on Text as shown below.

Then delete the code which is there and type the code as given below.

Code for Activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_margin="20dp"> <LinearLayout android:id="@+id/linearLayout1" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="20dp"> <EditText android:id="@+id/editText1" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:inputType="numberDecimal" android:textSize="20sp" /> <EditText android:id="@+id/editText2" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:inputType="numberDecimal" android:textSize="20sp" /> </LinearLayout> <LinearLayout android:id="@+id/linearLayout2" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="20dp"> <Button android:id="@+id/Add" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="+" android:textSize="30sp"/> <Button android:id="@+id/Sub" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="-" android:textSize="30sp"/> <Button android:id="@+id/Mul" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="*" android:textSize="30sp"/> <Button android:id="@+id/Div" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="/" android:textSize="30sp"/> </LinearLayout> <TextView android:id="@+id/textView" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="50dp" android:text="Answer is" android:textSize="30sp" android:gravity="center"/> </LinearLayout>

Now click on Design and your application will look as given below.

So now the designing part is completed.

Java Coding for the Android Application:

Click on app -> java -> com.example.exno3 -> MainActivity.

Then delete the code which is there and type the code as given below.

Code for MainActivity.java:

package com.example.devang.exno3; import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView; public class MainActivity extends AppCompatActivity implements OnClickListener
{ //Defining the Views EditText Num1; EditText Num2; Button Add; Button Sub; Button Mul; Button Div; TextView Result; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //Referring the Views Num1 = (EditText) findViewById(R.id.editText1); Num2 = (EditText) findViewById(R.id.editText2); Add = (Button) findViewById(R.id.Add); Sub = (Button) findViewById(R.id.Sub); Mul = (Button) findViewById(R.id.Mul); Div = (Button) findViewById(R.id.Div); Result = (TextView) findViewById(R.id.textView); // set a listener Add.setOnClickListener(this); Sub.setOnClickListener(this); Mul.setOnClickListener(this); Div.setOnClickListener(this); } @Override public void onClick (View v) { float num1 = 0; float num2 = 0; float result = 0; String oper = ""; // check if the fields are empty if (TextUtils.isEmpty(Num1.getText().toString()) || TextUtils.isEmpty(Num2.getText().toString())) return; // read EditText and fill variables with numbers num1 = Float.parseFloat(Num1.getText().toString()); num2 = Float.parseFloat(Num2.getText().toString()); // defines the button that has been clicked and performs the corresponding operation // write operation into oper, we will use it later for output switch (v.getId()) { case R.id.Add: oper = "+"; result = num1 + num2; break; case R.id.Sub: oper = "-"; result = num1 - num2; break; case R.id.Mul: oper = "*"; result = num1 * num2; break; case R.id.Div: oper = "/"; result = num1 / num2; break; default: break; } // form the output line Result.setText(num1 + " " + oper + " " + num2 + " = " + result); }
}