Mobile Application Development

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1 Mobile Application Development MTAT Jakob Mass

2 Goal Give you an idea of how to start developing mobile applications for Android Introduce the major concepts of Android applications, including: UI & UX principles and techniques Interacting with other applications and services, sensors Testing Walk you through: setting up the necessary development environment creating several sample applications Homeworks 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 2

3 References & Books Android developer portal Books Professional Android 4 Application Development, By Reto Meier. Wiley, 2010 (1 copy at J.Liivi library) The Busy Coder s Guide to Android Development, By Mark L. Murphy 2015 version is free (CC license) Android in Action by W. Frank Ableso, Robi Sen, Chris King, C. Enrique Ortiz. Manning, /09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 3

4 Dealing with problems & Help Practical Assistants: Jakob Mass ( jakob.mass@ut.ee ) Mohan Liyanage ( liyanage@ut.ee ) Google Group Post any questions & technical issues Help out others! 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 4

vision and concrete plans A Linux-based, multiprocess, multithreaded OS Each application is a different user By default, every app runs in its own Linux process.

5 What is Android? An open-source mobile platform Not just for phones TV, Watch, Smart Home Hub, Car Infotainment, Handheld GPS, Google, Open Handset Alliance 84 technology companies Commitment to openness, shared vision and concrete plans A Linux-based, multiprocess, multithreaded OS Each application is a different user By default, every app runs in its own Linux process. Each process has its own virtual machine, so an app's code runs in isolation from other apps. Libraries & Support tools Image: Wikimedia Commons user Wikideas1. The Android robot is reproduced or modified from work created and shared by Google and used according to terms described in the Creative Commons 3.0 Attribution License 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 5

6 Developing Applications You can write code for Android in Java, Kotlin or C/C++. (Not taking into account 3 rd party options) Today, Java is the most used language for Android Java package com.example.firstapp; import android.app.activity; public class MainActivity extends Activity { String name = John ; Kotlin package com.example.firstapp import android.app.activity class MainActivity : Activity() { var name = John protected void oncreate(bundle savedstate) { super.oncreate(savedinstancestate); } } override fun oncreate(savedinstancestate: Bundle?) { super.oncreate(savedstate) } 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 6

7 Software stack Image: 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 7

8 Android Software Stack Linux Kernel Foundation of the Android platform Provides key security features: User-based permissions model Process isolation Application Sandbox E.g., file permission management: one user cannot read/modify another user's files Thus, one application cannot see the files created by another application, except when explicitly shared by the developer Rooting Only the kernel and a small subset of the core applications run with root permissions It s possible to grant root access to applications, giving full access to system files, applications and all application data 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 8

9 Android Software Stack Hardware Abstraction Layer (HAL) Provides interfaces for accessing device hardware capabilities from the higher-level Java API. HAL is divided into various modules/libraries: Camera, Bluetooth, etc., /09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 9

10 Android Software Stack Android Runtime Provides an environment to host applications Applications run using ART (Android Runtime) Since Android v5.0 (API level 21) Before, Dalvik was used Dalvik Executable (DEX) format bytecode format designed specially for Android ART takes care of: executing Dex bytecode specification 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 10

11 From source to execution Android Java Check out Comparative Analysis of Mobile App Reverse Engineering Methods on Dalvik and ART by Na et al. 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 11

12 Why Android/Dalvik Runtime? The runtime is optimized specifically for mobile applications Runs multiple VMs efficiently Each application has its own VM instance Minimal memory footprint Relies on Linux kernel for threading and low-level memory management 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 12

13 Android Software Stack Native C/C++ Libraries 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 13

Java API & System Apps https://developer.android.

14 Java API & System Apps 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 14

15 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 15

Supporting different versions.. https://developer.android.com/about/dashboards/ (August 2018) Version Codename API % 2.3.3-2.3.7 4.0.3-4.0.4 Gingerbread 10 0.3% Ice Cream Sandwich 15 0.

16 Supporting different versions.. (August 2018) Version Codename API % Gingerbread % Ice Cream Sandwich % 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu x % 4.2.x Jelly Bean % % 4.4 KitKat % % Lollipop % 6.0 Marshmallow % % Nougat % % Oreo %

17 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 17

Development Environment & Tools Android Studio, IntelliJ IDEA-based set of software tools Single, unified environment for developing Android Download manager for SDK versions Emulator Performance

18 Development Environment & Tools Android Studio, IntelliJ IDEA-based set of software tools Single, unified environment for developing Android Download manager for SDK versions Emulator Performance profiling Visual layout editing Testing tools (Formerly, Eclipse was used) 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 18

Getting Started I hope all of you have Android Studio installed If you haven t, download the SDK tools and platforms for API 28

19 Getting Started I hope all of you have Android Studio installed If you haven t, download the SDK tools and platforms for API /09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 19

20 Exercise: Creating a New Project 1. Create a New Android Studio Project minsdk 19 Choose Empty Activity template 2. Let s create an AVD (Android virtual device) 3. Run the application You should see a view with Hello, world! 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 20

21 Projects in Android Studio Applications are created as Gradle-based projects Gradle is a build automation-tool, it takes care of software development routines, such as compiling the source code executing tests download and configuration of dependencies or other libraries packaging the application and additional files Installing the application to a physical/virtual device and running it there /09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 21

Manifest file (Next slide) Source code Non-code resources XML-based UI layout definitions Images, icons Constants Build scripts of the project Generally, we work with the build.

22 Manifest file (Next slide) Source code Non-code resources XML-based UI layout definitions Images, icons Constants Build scripts of the project Generally, we work with the build.gradle files only, especially the module-level build.gradle file! 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 22

23 A look at Gradle configuration apply plugin: 'com.android.application' android { compilesdkversion 28 defaultconfig { applicationid "example.com.helloworld" minsdkversion 23 targetsdkversion 28 versioncode 1 versionname "1.0" testinstrumentationrunner "android.support.test.runner.androidjunitrunner" } buildtypes { release { minifyenabled false proguardfiles getdefaultproguardfile('proguard-android.txt'), 'proguardrules.pro' } } } dependencies { implementation filetree(dir: 'libs', include: ['*.jar']). testimplementation 'junit:junit:4.12 } 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 23

24 Application Manifest Each project must declare an AndroidManifest.xml file Describes essential information about the app to the build tools, the Android OS, and Google Play It declares for instance: The permissions that the app wishes to use Capabilities such as supported device configurations Metadata, such as the application package name The components of the app (Activities, Services, BroadcastReceivers,..), and the corresponding Java (Kotlin) class names 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 24

25 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 25

26 Security in Android As mentioned earlier, follows standard Linux guidelines Each application runs in its own process Process permissions are enforced at user level and group IDs are assigned to processes Finer grained permissions are then granted (revoked) per operations Apps declare permissions in the manifest 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 26

Application Design Philosophy Applications should be Lightweight Resources are constrained: if your app consumes too much RAM while in the background, it will get killed by the OS quickly!

27 Application Design Philosophy Applications should be Lightweight Resources are constrained: if your app consumes too much RAM while in the background, it will get killed by the OS quickly! Responsive The framework strongly discourages freeze-ups Secure, respectful of privacy Declare and ask for only the permissions you need, when you need them! Seamless Usability is key, the framework gives you lots of tools to support accessibility & localization options and storing, persisting data 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 27

28 Application priorities, process states Applications have limited control over their own lifecycles Recall that applications run in separate processes, each one in a separate instance of the ART virtual machine Memory and process management is handled by the runtime and kernel Runtime may kill some services in the background Being aware of application states & priorities is critical 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 28

29 Process lifecycle, state hierarchy 1. Foreground process (active process) Few simultaneously 2. Visible process Activity that is visible to the user on-screen but not in the foreground. E.g., if the foreground Activity is displayed as a dialog that allows the previous Activity to be seen behind it. 3. Service process such as background network data upload or download 4. Cached process 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 29

30 Android Activity lifecycle Apps move through states during the lifecycle. Understanding the lifecycle is crucial, to prevent: Apps crashing if the user receives a call or switches to another app while using your app Using valuable resources when the user is not actively using your app Loss of user s progress when they leave your app and return to it later Loss of progress or crashes when screen switches between landscape and portrait orientation 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 30

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32 Let s look at the default, empty activity public class MainActivity extends Activity { protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); } 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 32

33 Logging in Android Traditional System.out.println is generally not used on Android (output may not be visible, depending on device) Instead, use the frameworks logging mechanisms: android.util.log class and its methods For example, Log.v( String tag, String message) Tag: app name, view name, usually a constant per class Message: the actual log message Log.v(..), Log.i(..), Log.w(.. ), Log.e(..) Log messages appear in the LogCat component of the Android Studio interface 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 33

34 Exercise: Hello, LogCat! Write a message to the log output Put the statement in the onresume lifecycle method Verify that you can see the message in LogCat 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 34

35 Creating GUIs in Android Three approaches: Declaring in XML Programmatically Visually Android Studio Layout Editor 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 35

36 public class MainActivity extends Activity { protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); } Reference to XML-defined View 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 36

37 Exercise 1: Programmatic UI Let s create a vertical LinearLayout Add 2 buttons to it 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 37

38 XML-based approach Declarative approach Stored in /res/layout Straightforward XML vocabulary for view elements, such as widgets and layouts Declare the relationship and attributes of components During compiling, each XML layout is compiled into a View resource View resource is loaded via the setcontentview() method 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 38

Exercise 2: XML-based UI Re-create the same LinearLayout activity using XML In res/layout, choose New-> Layout resource File Replace the default Root

39 Exercise 2: XML-based UI Re-create the same LinearLayout activity using XML In res/layout, choose New-> Layout resource File Replace the default Root element with LinearLayout! We will look into the default option later 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 39

40 Troubleshooting Shouldn t be seeing errors here! If your XML is correct, but you re not seeing anything in the Design view Quick workaround: Change the Editor s theme from AppTheme to something else (e.g. Material Light) There seems to be a bug in the latest versions of com.android.support:appcompat support library 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 40

String resources Notice the warnings the IDE shows you Android provides a system of managing resources like strings, numbers, colors, etc Open app > res

41 String resources Notice the warnings the IDE shows you Android provides a system of managing resources like strings, numbers, colors, etc Open app > res > values > strings.xml. Create a string value Use it for your button 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 42

42 Working with string resources strings.xml: <string name="hello">greetings!</string> <string-array name="planets_array"> <item>mercury</item> <item>venus</item> <item>earth</item> </string-array> <string name="message">hello, %1$s.</string> Java: // Single string String string = getstring(r.string.hello); /// String array Resources res = getresources(); String[] planets = res.getstringarray(r.array.planets_array); // Formatted string String text = getstring(r.string.message, username); 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 43

43 Other resources Colour accessed via the R.color class getresources().getcolor(r.color.pink) <resources> <color name="blue">#3f51b5</color> <color name="pink">#ff4081</color> </resources> Style, dimension resources Accessed from the R.style, R.dimen classes Define various UI aspects such as margins, action bar configurations 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 44

44 Resource file benefits Separation of code & concerns Easy to find, update e.g no hardcoded strings, colours in code Organizing, structuring resources Localization Screen orientation Device type (tablet vs phone) Not just strings & layouts! Color schemes Etc 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 45

45 Supporting different screens Create additional res/layout directories for alternative layouts Smallest width: Available width: Orientation: 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 46

46 Localizing applications Support different languages with res/values-en res/values-fr res/values-est ISO 639 language codes Works for any resource strings, mipmap images, /09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 47

47 So far Programmatic UI approach Declarative, XML-based UI approach Working with resources Strings Colours Localization options 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 48

48 Coming back to screen sizes You should minimize hard-coding the position and size of your UI components or creating an alternative layout for every possible configuration Instead, build UI-s with flexible layouts, that stretch and adapt to the current size based on a set of rules (constraints) ConstraintLayout easiest way to create a responsive layout 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 49

49 Visual approach: the Layout Editor 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 50

50 ConstraintLayout 101 Every object must have: At least 1 horizontal constraint At least 1 vertical constraint Centering objects: Use 2 constraints on the same axis Next week we will have a more detailed look at ConstraintLayout 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 51

51 Exercise 3: Re-create the UI with ConstraintLayout Do NOT use the auto-converter tool! 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 52

52 Simple user interaction Let s handle button clicks With the findviewbyid(..) method, you can get a handle for referencing XML-declared resources & view objects in code: Button button = findviewbyid(r.id.buttona); button.setonclicklistener(new View.OnClickListener() public void onclick(view view) { //do something } }); 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 54

53 Specifying click handler from XML Alternatively, in XML Specify the click handler with the Button attribute android:onclick,setting its value to the method which will be called Create the corresponding method in the Activity public void handleclick(view view) { // Do something in response to button click } 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 55

54 Advantages of Declarative approach Separation of appearance (presentation) from state-changing code (business logic) Can change interface without having to completely recompile Java View Resource is inflated at runtime 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 56

55 Exercise 4: Click counter Set up a click handler that updates the button to show the number of times it has been clicked Make the 2nd button restart the counter Try both the programmatic & declarative approach 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 57

56 Recap The Android Project Android Studio & Virtual Devices Application Lifecycle Working with resources Localization Screens, Languages Basic UI creation & interaction ConstraintLayout OnClick events 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 58

user input Use the settext, gettext methods and click listeners Create separate portrait and

57 Homework. Task 1 Implement a Celsius-Fahrenheit converter Should convert both ways Use EditText to get user input Use the settext, gettext methods and click listeners Create separate portrait and landscape mode UI-s (using XML): Portrait mode with LinearLayout Landscape mode with ConstraintLayout 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 59

58 Homework. Task 2 Observe the application lifecycle Override the onpause, onresume, onstop, ondestroy, oncreate lifecycle methods and with the help of logging answer these questions: Which of these methods are called & what order are they called in when: Changing device orientation? Hitting the home button and returning to the application Hitting the back button and re-opening the application What happens to the EditText and TextView elements in each of these 3 cases (assuming the user has at least done 1 successful conversion)? 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 60

59 Homework 1 additional info Deadline: before next lecture Submission: via the courses.cs.ut.ee page for this course You can also find a slightly more detailed explanation of the homework there 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 61

60 Next lecture Views & Layouts Fragments Events, Intents Application components 07/09/2018 Mobile & Cloud Lab. Institute of Computer Science, University of Tartu 62

Mobile Application Development - Android

Mobile Application Development - Android MTAT.03.262 Satish Srirama satish.srirama@ut.ee Goal Give you an idea of how to start developing Android applications Introduce major Android application concepts