Question

Your task is to build an Android application that satisfies the following requirements:

• Has two activities: MainActivity that implements the main functionality of the application and AboutActivity that shows your full name as per college record and student id

• The AboutActivity should be available through a menu

• A back button should appear in the ActionBar of the AboutActivity that takes user back

  to the MainActivity. It should be done through configuration!

• MainActivity should implement the following functionality

  o read the following input from the user: § number of hours worked

  § hourly rate
  o calculate the pay using the following formula

  § if no of hours is less or equal than 40 then pay=no_of_hours*hourly_rate

  § else, pay=(no_of_hours-40)*hourly_rate*1.5 + 40*hourly_rate o calculate the tax using the following formula

  § tax=pay*0.18
  o present following data to the user

§ pay
§ overtime pay § total pay
§ tax

Answer 1

Hi there! You first need to create a new project and then add the required files. I have attached screenshots for steps and added comments for explanation in code. I have also attached screenshots of the app. Please upvote if it helped.

Steps to create new Project

1. Open Android Studio:

2. Click on Start a new Android Studio Project:

3.Create a new project on Android Studio(with an Empty Activity and package name as com.project.taxcalculator and Application Name of your choice):

Creation of the required files

Since we need menu to navigate to AboutActivity I will first show you how to create a menu xml file.

1. Make sure that you are in the Project type structure as shown in the following picture and then navigate to app->src->res and right click on res and then follow New->Android Resource File(If you cannot see the panel on the left press Alt+1)

2. Then in the following pop-up, select the resource type as menu and file name as menu.xml and click on OK.

3. Copy paste the following contents to app->res->menu->menu.xml created.

menu.xml

<?xml version="1.0" encoding="utf-8"?>
<!--XML file for creating a menu with a single item-->
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/about_me"
        android:title="About me" />
</menu>

Copy paste the code in the following respective files:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<!--A linearlayout is used to display elements in a linear fashion, either horizontally or vertically-->
<!--the horizontal or vertical fashion can be specified using the orientation attribute of linearlayout-->
<!--Created a vertical linearlayout of horizontal linearlayouts-->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="30dp"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
<!--A layout_weight attribute gives us control about the space occupied by any element inside a linearlayout-->
<!--layout_weight:1 helps us evenly distribute the space between the children of a linearlayout        -->
<!--since width is controlled by weight we specify width as 0px-->
        <TextView
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Number of hours worked: " />

        <EditText
            android:id="@+id/num_hours_edit_text"
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Hourly rate: " />

        <EditText
            android:id="@+id/hourly_rate_edit_text"
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1" />
    </LinearLayout>
<!--This button will be used for calculating and displaying tax and pay-->
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:onClick="calculateTaxAndPay"
        android:text="Calculate Tax and Pay" />

<!--All the following elements are used for displaying output-->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Pay: " />

        <TextView
            android:id="@+id/pay_text_view"
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Overtime pay: " />

        <TextView
            android:id="@+id/overtime_pay_text_view"
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Total pay: " />

        <TextView
            android:id="@+id/total_pay_text_view"
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Tax: " />

        <TextView
            android:id="@+id/tax_text_view"
            android:layout_width="0px"
            android:layout_height="wrap_content"
            android:layout_weight="1" />
    </LinearLayout>
</LinearLayout>

MainActivity.java

package com.project.taxcalculator;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    //creating EditTexts and TextViews as global variables so that they can be accessible inside the onClick method calculateTaxAndPay
    EditText noOfHoursEditText;
    EditText hourlyRateEditText;
    TextView payTextView, overtimePayTextView, totalPayTextView, taxTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // we need to get the EditTexts and TextViews we defined in XML into our Java file in order to take input and display output to the user
        // we do it by specifying an Id in XML file and referencing the Id to fetch the elements in Java code
        // these EditTexts are used for taking input from the user
        noOfHoursEditText = findViewById(R.id.num_hours_edit_text);
        hourlyRateEditText = findViewById(R.id.hourly_rate_edit_text);
        // these TextViews are used for displaying output to the user
        payTextView = findViewById(R.id.pay_text_view);
        overtimePayTextView = findViewById(R.id.overtime_pay_text_view);
        totalPayTextView = findViewById(R.id.total_pay_text_view);
        taxTextView = findViewById(R.id.tax_text_view);
    }

    // as we have specified this method in the onClick attribute of our button, this method will be called if the user clicks on the button
    public void calculateTaxAndPay(View view) {
        try {
            // after the button is clicked we fetch the data entered in the EditTexts using getText and toString methods
            // we then convert the string into double type using parseDouble method
            double noOfHoursWorked = Double.parseDouble(noOfHoursEditText.getText().toString());
            double hourlyRate = Double.parseDouble(hourlyRateEditText.getText().toString());
            // initializing methods for displaying in the output
            double pay = 0;
            double overtimePay = 0;
            double totalPay = 0;
            double tax = 0;
            // calculating the output using the given formulas
            if (noOfHoursWorked <= 40) {
                pay = noOfHoursWorked * hourlyRate;
                overtimePay = 0;
                totalPay = pay;
            } else {
                pay = 40 * hourlyRate;
                overtimePay = (noOfHoursWorked - 40) * hourlyRate;
                totalPay = pay + overtimePay;
            }
            tax = totalPay * 0.18;
            // displaying the output to the user by using setText method on TextViews
            // also used String format method in order to show only decimal places for double values
            payTextView.setText(String.format("%.2f", pay));
            overtimePayTextView.setText(String.format("%.2f", overtimePay));
            totalPayTextView.setText(String.format("%.2f", totalPay));
            taxTextView.setText(String.format("%.2f", tax));
        } catch (NumberFormatException nfe) {
            // If the user does not give valid input a toast message will be displayed
            Toast.makeText(this, "Invalid input!", Toast.LENGTH_SHORT).show();
        }
    }

    // this method is used to inflate(render) the menu from the XML file
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu, menu);
        return true;
    }

    // this method is used to implement functionality when any of the menu items are clicked
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
            case R.id.about_me:
                // startActivity method is used to navigate from one activity to another
                startActivity(new Intent(MainActivity.this, AboutActivity.class));
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

Then create a new activity by right clicking on java->New->Activity->Empty Activity from the right pane as shown in the picture:

Then type in AboutActivity under Activity Name and click Finish

activity_about.xml(here in the TextView you need to type in your name and student id) For example Developed by Andrew\nStudent Id: 12345

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<!--You can change your name and Student Id below-->
<!--layout_centerInParent attribute will center the textview for us-->
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Developed by x\nStudent Id: 123" />
</RelativeLayout>

AboutActivity.java

package com.project.taxcalculator;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class AboutActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_about);
    }
}

AndroidManifest.xml

You need to add parentActivityName attribute for AboutActivity in AndroidManifest.xml.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.project.taxcalculator">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
<!--parentActivityName attribute is used to implement the back functionality using configuration as mentioned in the question-->
        <activity
            android:name=".AboutActivity"
            android:parentActivityName=".MainActivity"></activity>
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity screenshot

AboutActivity Screenshot(You can add your details by going on activity_about.xml)

Dont forget to upvote!