01 - Android Intro

Topics

Android overview
Basic Android Studio usage
Kotlin language
UI creation
App lifecycle and state
Local storage and data access (SQLite)
Sensors (proximity, geomagnetic, motion, GPS, …)
Web services (REST API)
Modern architecture

Android

Operating system, devised for mobile equipment (mostly)

Usage: phones, tablets, TV-s, watches, glasses, cars, laptops, cameras, game consoles, …

Market share among smartphones – ca 85% (iOS 14%)

Open-source project

Google apps and services are closed source (mail, map, etc.)

History

2003 – founded (lead: Andy Rubin)
- Initial idea – OS for cameras
- New plan – Mobile OS, (others: Symbian/Nokia and Win Mobile)
2005 – Google acquires the whole project
2007 – Open Handset Alliance
- Google, HTC, Sony, Samsung, Dell, Motorola, LG, Qualcomm, Intel, etc…
2008 – Android 1.0 (HTC Dream, no touchscreen)
2009 – Android 1.5 Cupcake (iPhone 2007, iPhone 3G 2008)
2010 – Android 2.2 Froyo, 2.3 Gingerbread
2011 – Android 3.0 Honeycomb (tablets only)
2011 - Android 4.0 Ice Cream Sandwich
- HOLO UI
2014 - Android 5 Lollipop
- Material design
- Dalvik vs ART (Android Runtime) (JIT or precompile, garbage collection)
2015 - Android 6 Marshmallow
2016 – Android 7 Nougat
2017 – Android 8 Oreo
2018 – Android 9 Pie
2019 – Android 10 Q – moves closer to iOS, security clamped down

Version distribution

2020

Pie – 9.X – 10%
Oreo – 8.X – 28%
Nougat – 7.X - 19%
Marshmallow – 6.X – 17%
Lollipop - 5.X – 14%
KitKat – 4.4 – 7%
4.4 and higher - ca 95%

Market

Latest info (2022)

17 Jelly Bean 99.8%
19 KitKat 99.4%
22 LolliPop 97.3%
23 Nougat 85.6%
27 Oreo 78.7%
28 Pie 69%
29 Android 10 50.8%
30 Android 11 24.3%

Android Architecture

Market

App types

NDK - C/C++
- Close to hardware and operating system
SDK - Native <- this course!!!!
- Kotlin/Java (ART/Dalvik), using system libraries
Hybrid – React Native, Ionic, etc.
Cross platform – Xamarin (C#), Flutter (Dart) etc.
Html/JS – Progressive Web Apps
- One codebase/layout for different platforms
- Problems with UI, weak access to hardware
There is also course on Hybrid Mobile Apps - ICD0018 (fall semester)

App architecture - AndroidManifest.xml

The manifest file presents essential information about your app to the Android system, information the system must have before it can run any of the app's code.
Describes the components of the application — the activities, services, broadcast receivers, and content providers that the application is composed of.
Declares which permissions the application must have in order to access protected parts of the API and interact with other applications.
Declares hardware requirements.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.akaver.demo01">

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.INTERNET" />

    <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/Theme.Demo01">

       <service
            android:name=".MyBgrService"
            android:enabled="true"
            android:exported="false"></service>

        <activity
            android:name=".ActivitySecond"
            android:exported="true" />

        <activity android:name=".MainActivity" android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

App architecture - build.gradle (app)

Declares the minimum level of the Android API that the application requires (minSdk).
Additional libraries (dependencies)

plugins {
    id 'com.android.application'
    id 'kotlin-android'
}

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.akaver.demo01"
        minSdk 22
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.2'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    implementation 'com.google.android.gms:play-services-maps:17.0.0'
    implementation 'com.android.volley:volley:1.2.1'
}

App code

MainActivity.kt

package com.akaver.demo01

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
}

actvity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

UI generated from XML

Market

Other resources

Images
Animations
Menu
Strings
Misc files

APK

Android Application Package
ZIP file, combines all the resources and java bytecode
Signed with developer key
Developer key must be the same from version to next version
- Don’t lose your keys (passwords)
Android Studio takes care of APK creation
APK-s can be downloaded from store, using 3-rd party utilities
Resources can be used as is
Most elements/code can be decompiled/recompiled

Google Play - app store

Almost no review process
Problems are dealt with afterwards
App hijacking, etc. are real problems

App security

Every app works in its own private virtual machine (Zygote)
Need permission for system resources/hardware
- confirmed on app install
- reconfirmed when app has not been used for some time
Data is private, no other app can access directly other app data
Everything is possible on rooted device
End user is the weakest link

Developer problems

Gazillion different hardware devices and capabilities
Lots of different Android implementations
- Samsung TouchWiz
- HTC Sense
- ...
Migration to newer versions very slow (or not done at all)
Rooted phones
Ca 2X time spent on development compared to iOS
Ca 60% better income on iOS

Testing on devices

Market Market

Device variability

Market Market

Other hardware

Market Market Market Market Market

Hands on demo time - Notes

findViewById vs
Add kotlin-android-extensions to build.gradle (deprecated) for initial view elemnts to code binding.

plugins {
    id 'com.android.application'
    id 'kotlin-android'
}

apply plugin: 'kotlin-android-extensions'

Remove virtual keyboard from screen when done with it

fun buttonGreetClicked(view: View) {
    textViewGreeting.text = "Hello, " + editTextName.text + "!"
    val inputMethodManager = getSystemService(INPUT_METHOD_SERVICE) as InputMethodManager
    inputMethodManager.hideSoftInputFromWindow(getCurrentFocus()?.windowToken, 0)
}