To create Basic Calculator App > Android App Development

To Develop Basic Calculator App > Android 

Mobile Computation and Computing

PROGRAM:

MainActivity.java

package com.example.root.pratdroid;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.EditText;

import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    EditText no1, no2;

    TextView result,symbol;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        no1 = (EditText) findViewById(R.id.editText);

        no2 = (EditText) findViewById(R.id.editText2);

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

        symbol = (TextView) findViewById(R.id.textView3);

    }

    public void onButtonClick(View v)

    {

        Double n1,n2,r=0.0;

        String sym="";

        n1=Double.parseDouble(no1.getText().toString());

        n2=Double.parseDouble(no2.getText().toString());

        switch (v.getId()){

            case R.id.button:

                r=n1+n2;

                sym="+";

                break;

            case R.id.button2:

                r=n1-n2;

                sym="-";

                break;

            case R.id.button3:

                r=n1*n2;

                sym="*";

                break;

            case R.id.button4:

                r=n1/n2;

                sym="/";

                break;

        }

        result.setText(r+"");

        symbol.setText(sym);

    }

}

activity_main.xml

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

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.example.root.pratdroid.MainActivity">

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Hello World!"

        android:id="@+id/textView" />

    <EditText

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:inputType="number"

        android:ems="10"

        android:id="@+id/editText"

        android:layout_centerHorizontal="true"

        android:layout_below="@+id/textView" />

    <EditText

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:inputType="number"

        android:ems="10"

        android:id="@+id/editText2"

        android:layout_above="@+id/textView2"

        android:layout_alignStart="@+id/editText" />

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="New Text"

        android:id="@+id/textView2"

        android:layout_above="@+id/button"

        android:layout_centerHorizontal="true"

        android:layout_marginBottom="42dp" />

    <Button

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Add"

        android:id="@+id/button"

        android:onClick="onButtonClick"

        android:layout_above="@+id/button2"

        android:layout_alignStart="@+id/button3" />

    <Button

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Subtract"

        android:id="@+id/button2"

        android:onClick="onButtonClick"

        android:layout_above="@+id/button3"

        android:layout_centerHorizontal="true" />

    <Button

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Multiply"

        android:id="@+id/button3"

        android:onClick="onButtonClick"

        android:layout_above="@+id/button4"

        android:layout_alignEnd="@+id/button2" />

    <Button

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Divide"

        android:id="@+id/button4"

        android:onClick="onButtonClick"

        android:layout_alignParentBottom="true"

        android:layout_alignStart="@+id/button3"

        android:layout_marginBottom="42dp" />

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textAppearance="?android:attr/textAppearanceMedium"

        android:text="Medium Text"

        android:id="@+id/textView3"

        android:layout_above="@+id/editText2"

        android:layout_centerHorizontal="true" />

</RelativeLayout>

Output: