The JUST JAVA project from Udacity lesson of Android basics.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="16dp"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="16dp"
    tools:context="com.example.android.justjava.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:text="Quantity:"
        android:textAllCaps="true" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:orientation="horizontal">

        <Button
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:onClick="decrement"
            android:text="-" />

        <TextView
            android:id="@+id/quantity_text_view"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:paddingLeft="8dp"
            android:paddingRight="8dp"
            android:text="1"
            android:textColor="@android:color/black"
            android:textSize="16sp" />

        <Button
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:onClick="increment"
            android:text="+" />

    </LinearLayout>


    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:text="Price"
        android:textAllCaps="true" />

    <TextView
        android:id="@+id/price_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="5€"
        android:textColor="@android:color/black"
        android:textSize="16sp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:onClick="submitOrder"
        android:text="order" />
</LinearLayout>

MainActivity.java

// Add your package below

package com.example.android.justjava;


import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;

import java.text.NumberFormat;

/**
 * This app displays an order form to order coffee.
 */

public class MainActivity extends AppCompatActivity {


    int quantity = 1;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }


    /**
     * This method is called when the order button is clicked.
     */

    public void submitOrder(View view) {

        int price = quantity * 5;

        String priceMessage = "Total: " + price + "€";

        priceMessage = priceMessage + "\nThank you!";

        displayMessage(priceMessage);

    }


    /**
     * This method displays the given quantity value on the screen.
     */

    private void display(int number) {

        TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);

        quantityTextView.setText("" + number);

    }

    /**
     * This method displays the given price on the screen.
     */

    private void displayPrice(int number) {

        TextView priceTextView = (TextView) findViewById(R.id.price_text_view);

        priceTextView.setText(NumberFormat.getCurrencyInstance().format(number));

    }

    /**
     * This method displays the given message on the screen.
     */

    private void displayMessage(String message) {

        TextView priceTextView = (TextView) findViewById(R.id.price_text_view);

        priceTextView.setText(message);

    }

    /**
     * This method increments quantity value.
     */

    public void increment(View view) {


        quantity = quantity + 1;
        display(quantity);

    }

    /**
     * This method decrements quantity value.
     */

    public void decrement(View view) {


        quantity = quantity - 1;
        display(quantity);

    }
}