Building first android application

1. Building first android application Dr. Razi Iqbal razi.iqbal@leads.edu.pk

2. Create a new Android Application

3. Create a new Android Application • Application Name • Name of the App / Project • Project Name • Used by Eclipse and should be unique within a workspace • Package Name • It is collection of Classes. Should be same for the lifetime of the app • Should be like com.razi.helloWorld • Minimum SDK • Lowest SDK that app will support. • Will support more devices and less features • Target SDK • Highest SDK an app supports • Compile with • Compiles with Highest API level. • Theme • Base theme for the project

4. Android Versions

5. Create a new Android Application

6. Hello World Android Application

7. Hello World Android Application

8. Creating Emulator

9. Creating New Run Configuration • ADT automatically creates Run Configuration • If that doesn’t suit a developer, new run configurations can be built. • Used for Customized Configurations • Emulator • Project • Activity

10. Creating New Run Configuration

11. Hello World Console • Contains all the tasks performed for the Project • ADB is Android Debug Bridge

12. Project Components (Package Explorer) • src • It is source folder of the project • Contains the Package • com.razi.helloworld • The package contains .java file • MainActivity.java • Built during the new project wizard • src folder can have more than one package • Sometimes apps use different user packages • For Example • One for Web Access • One for Creating GUI

13. Project Components (Package Explorer) • assets • It contains all the assets of the project • Normally will contain • Databases • Dictionaries • Read data from the assets • Accessed with • streams of bytes • Converted into Objects • Using proper methods

14. Project Components (Package Explorer) • bin • Contains files built by ADT during build process • It contains all important .apk file • .apk is Android Package File • It is like exe file for windows • It’s a binary • It contains everything needed by Android app

15. Project Components (Package Explorer) • res • Contains all the resources for the app • Icons, Images etc • Menus • Layouts • Activity_main.xml • Layout of the Activity • values • Strings.xml

16. Project Components (Package Explorer) • gen • Its ADT generated folder • Files in this folder should not be changed manually • It contains • BuildConfig.java • R.java • R.java class is used • To reference the resources of the project in res folder • Each member of res has a class in R.java and contains all the members in that class • Don’t worry about Hex values

17. AndroidManifest.xml 1 2 3

18. AndroidManifest.xml • Provides the package name which is a unique identifier • Provides the version code • It is an integer value • Next values should be greater than the previous values • It is used for updates • Google Play knows when to inform user about updates based on this code • Code is not visible to the user • Provides version name • It’s a string value • <major>.<minor>.<point> e.g. 2.1.2 • It is used to display it to user • It can be anything like Date e.g. 2010-06-28 1

19. AndroidManifest.xml • Provides minimum SDK version • Use to run the apps on minimum OS • Normally should be minimum OS to support more devices • Provides Target SDK version • Maximum SDK version • SDK in which the app is built and tested • Should be latest SDK to support latest features 2

20. AndroidManifest.xml • Provides Launcher Icon • Available in Drawable folder under res. • Provides App Label • Label for the application • The Label is stored in strings.xml file • Provides App Theme • Theme for the app • Available in styles.xml file • Provides Activity • There is one activity • Activity is handled by MainActivity.java in src folder • Label for the Activity is the same as app name under strings.xml 3

21. strings.xml • Available under res  values • Contains strings for the project (app) • All strings should be in this xml file • Strings are in this file so that localization is easy • If in future the app is to be converted into some other language only strings in this file will be converted • It contains • Name (the name of the string e.g. app_name) • Value (the value of the string e.g. Hello World)

22. activity_main.xml • xmlns: android and xmlns:tools are the namespaces • .MainActivity tells this layout is for MainActivity.java file • @dimen and @string are defined in R.java

23. colors.xml • Add new XML file for colors in res  values • Name it colors.xml • Copy paste colors in the file • Save it • Use it like this • @color/Red android:textColor="@color/Red" To change the Font size android:textSize="40sp"

24. Adding a Button • Add new Button by dragging and Dropping • Change Text to “Click Me!” • Placement will be relative to Text View • Check for R.java class • It will add a new button1 in id class • This is done after building the project

25. MainActivity.java 1 2 3 4

26. MainActivity.java • Package for current App • Developed during New Project Wizard • It contains the App • A Project can have Multiple Packages 1 • Using Android Available Packages • In order to use classes, we have to import Packages • Different packages are imported in this case • import android.os.Bundle; • import android.app.Activity; • import android.view.Menu; 2

27. MainActivity.java • Inherit MainActivity from Activity Class • Our MainActivity class is subclass of Activity • Activity Class contains many methods • MainActivity can use these methods 3 • onCreate is a methods in Activity class • @Override is used to tell the compiler we are overriding the superclass method • App will compile without it also but better use it 4

28. Change text on Button Click

29. Anonymous Inner Class

30. Updated Hello World Code