1. Android Application Model I
CSE 5236: Mobile Application Development
Instructor: Adam C. Champion, Ph.D.
Course Coordinator: Dr. Rajiv Ramnath
Reading: Big Nerd Ranch Guide, Chapters 3, 5 (Activities); Chapter 13 (menus)

2. Android Framework Support
Walk through components
Explain drivers – these connect the hardware components to the OS
Could we have used libc and c interface to drivers to get access to everything in OS using Java? Why write libraries in C?
Performance?
Have you heard of Java JNI? Build Java layer on top of C.

3. Framework Capabilities and Add-Ons
Built-In Services:
GUI
OS services (file I/O, threads, device management)
Graphics
Device access (GPS, camera, media players, sensors),
Networking
Standard language libraries
Add-ons:
Google Play services (e.g. Google Maps, Games, etc.)
Database support (SQLite)
WebKit/Chromium
Framework tailored to mobile apps?
How?
Built in services that could be used by any kind of app.
Add ons
Maps. DB support, Webkit
Why separated?

4. Tooling Support IDE: Android Studio Testing tools: JUnit, Espresso
Performance profiling tools: Android Profiler
Source code management: Git, Subversion, CVS, etc.
Software emulators: Android emulator, Intel HAXM, Genymotion
Sensor injection via emulator

5. Android Studio Project Components
Go over the following directories:
Src = source
Gen = generated code (R.java)
Android SDK version
assets = application specific types of resources (i.e. non-standard resources)
res = resources
go over drawable, layout, menu, raw and values
AndroidManifest.xml file
Activities, intents
project.properties file – project settings

6. Types of Android Programs
Applications
Home app, Home screen
Take over screen
Services
Run in the background without UI
App widgets and home screen widgets
View-only interface to a service
Home screen widget if on Home screen
All apps have Activities – a key part of any Android app

7. Activities in Tic-Tac-Toe
Refer to layout files for each one

8. Specifying Activities – AndroidManifest.xml
<activity android:name=".SplashScreen" android:screenOrientation="portrait"> <intent-filter> <action android:name="android.intent.action.MAIN"/> <category android:name="android.intent.category.LAUNCHER”/> </intent-filter> </activity> <activity android:name=".Login" android:launchMode="singleInstance" <action android:name="com.wiley.fordummies.androidsdk.Login"/> <category android:name="android.intent.category.DEFAULT"/>
App name
Orientation
Intent filter – invocation messages the activity will respond to.
Services
Launch mode (talk about tasks)
Discussion: Why have concept of activities? Ans: High-grain element of reuse

9. Implementing Activities
Java
Kotlin
public class LoginActivity extends SingleFragmentActivity { ... } public class GameSessionActivity extends SingleFragmentActivity {
class LoginActivity : SingleFragmentActivity() { ... } class GameSessionActivity : SingleFragmentActivity() {
Difference between Login and GameSession. Login implements its own UI.
GameSession delegates its UI to another class (subclass of View). Only has passive UI elements
Walk through these two activities
SingleFragmentActivity is an interface with one method, createFragment(), for creating activities with just one fragment
Note: SingleFragmentActivity extends FragmentActivity

10. Specified declaratively in layout files Always use Fragments…
Activity UI
Widgets
View and ViewGroup
Package android.view
Specified declaratively in layout files
Always use Fragments…

11. Sample Layout: Login Activity
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="20dip">
<LinearLayout android:orientation="vertical
. . .
<TextView />
<TextView />
<EditText />
<Button />
</LinearLayout>
</ScrollView>
<project>/app/src/main/res/layout/fragment_login.xml

12. Views, ViewGroups, Layouts, Widgets
Many types of views, layouts and widgets:
ScrollView, HorizontalScrollView
LinearLayout, AbsoluteLayout, FrameLayout, RelativeLayout
TextView, EditText, Button, DatePicker, Spinner
Nested nature of layout
ViewGroup base class for composite elements
View base class for terminal UI components
Layout files “compiled” into resource R class in res subtree
A ViewGroup is a special view that can contain other views (called children.)
Superclass of Layout and specific collection views: Datepicker, Calendarview

13. Implement UI Logic: Listener Objects: Java
public class LoginActivity extends SingleFragmentActivity { // Create LoginFragment in onCreate() method. (See SingleFragmentActivity) } public class LoginFragment extends Fragment implements View.OnClickListener { private EditText mUsernameEditText; private EditText mPasswordEditText; . . public View onCreateView(. . .) { // The real code has many null checks and screen rotation check (omitted for brevity) View v = inflater.inflate(R.layout.fragment_login, container, false); mUsernameEditText = v.findViewById(R.id.username_text); mPasswordEditText = v.findViewById(R.id.password_text); Button loginButton = v.findViewById(R.id.login_button); loginButton.setOnClickListener(this); Button cancelButton = v.findViewById(R.id.cancel_button); cancelButton.setOnClickListener(this); Button newUserButton = v.findViewById(R.id.new_user_button); newUserButton.setOnClickListener(this); return v; }
Ask students to view Login class
How layout is inflated
How to access a button
How to attach listeners

14. Implement UI Logic: Listener Objects: Kotlin
class LoginActivity : SingleFragmentActivity() { // Create LoginFragment in onCreate() method. (See SingleFragmentActivity) } class LoginFragment : Fragment(), View.OnClickListener { private lateinit var mUsernameEditText: EditText private lateinit var mPasswordEditText: EditText override fun onCreateView(. . . ): View? { // Similarly, real code has screen rotation check (omitted for brevity) val v = inflater.inflate(R.layout.fragment_login, container, false) mUsernameEditText = v.findViewById(R.id.username_text) mPasswordEditText = v.findViewById (R.id.password_text) val loginButton = v.findViewById(R.id.login_button) loginButton.setOnClickListener(this) val cancelButton = v.findViewById(R.id.cancel_button) cancelButton.setOnClickListener(this) val newUserButton = v.findViewById(R.id.new_user_button) newUserButton.setOnClickListener(this) return v } // . . .

15. The OnClick Handler Java Kotlin Kotlin’s ?. operator is short for:
public void onClick(View v) { switch (v.getId()) { case R.id.login_button: checkLogin(); break; case R.id.cancel_button: finish(); case R.id.new_user_button: FragmentManager fm = getFragmentManager(); Fragment fragment = new AccountFragment(); fm.beginTransaction() .replace(/* container */, fragment) .addToBackStack("account_fragment") .commit(); } // Null check code omitted }
override fun onClick(view: View) { when (view.id) { R.id.login_button -> checkLogin() R.id.cancel_button -> activity?.finish() R.id.new_user_button -> val fm = fragmentManager fm?.beginTransaction() ?.replace(/* container */, fragment) ?.addToBackStack(. . .) ?.commit() } }
Why one callback for all buttons? Why not separate onclick call backs? Like, say, iOS
Ans: Could do that. Convention.
Kotlin’s ?. operator is short for:
if (object != null) {
object.callMethod() }

16. Embedding a View: GameSession Activity, Fragment: Java
public class GameSessionActivity extends SingleFragmentActivity {
. . . }
public class GameSessionFragment extends Fragment {
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=" . . >
<LinearLayout
...
<com.wiley.fordummies.androidsdk.Board
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</LinearLayout>
<TextView ... "/>
Board is a custom view. Ask students to view in Eclipse

17. Embedding a View: GameSession Activity, Fragment: Kotlin
class GameSessionActivity : SingleFragmentActivity() { } class GameSessionFragment : Fragment() { <!-- Same XML as before -->

18. Embedding a View: Board Class
Java
Kotlin
// Board.java public class Board extends View { ... public boolean onTouchEvent( MotionEvent event) { switch (action) { case MotionEvent.ACTION_DOWN: break; } return super.onTouchEvent(event); } }
// Board.kt class Board : View { override fun onTouchEvent( event: MotionEvent): Boolean { when (action) { MotionEvent.ACTION_DOWN -> { } } return super.onTouchEvent(event) } }
Ask students to view Board implements onTouchEvent callback

19. Handling UI in the Activity
Activity also a View
Can handle UI without any widgets. Why?
Handle non-widget-specific events (touch)
Handle user interaction outside the boundaries of any UI components
See onTouchEvent method in SplashScreenFragment class.

20. Menus (Option menus) and Action Bars
Declare the menu items
Define onCreateOptionsMenu() and/or the onCreateContextMenu() callback methods in Activity. Automatically called to create the menu (what if it doesn’t exist?).
Implement onOptionsItemSelected() and/or onContextItemSelected() in activity.
Why menus? Talk about action bar.
Briefly mention context menus (pop-up menus)

21. Menu Layout File
<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android=" <item android:title="Settings" /> <item android:title="Help" <item android:title="Exit" <item android:title="Contacts" </menu>
Ask students to view menu.xml
Ask students to view menu_ingame.xml
It should be obvious that this layout file defines four items, named Settings, Help, Exit, and Contacts, respectively. The identifiers for these items are menu_settings, menu_help, menu_exit, and menu_contacts respectively. Icons for @android:drawable/ic_menu_close_clear_cancel and are standard icons in the Android SDK. This layout file is compiled into resources specified in the R class in the gen subtree of the Android project.
Action Bar: Declare menu item with additional attribute
android:showAsAction ="ifRoom","never","withText" or "always".

22. Menu Creation: Java
public class GameOptionsFragment { ... public View onCreateView(…) { // setHasOptionsMenu(true); } public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu, inflater); inflater.inflate(R.menu.menu, menu);
Ask students to view GameOptions onCreateOptionsMenu method where menu is inflated.
Ask students to view GameSession onCreateOptionsMenu

23. Menu Creation: Kotlin
class GameOptionsFragment { override fun onCreateView(…) { // setHasOptionsMenu(true); } override fun onCreateOptionsMenu( menu: Menu, inflater: MenuInflater) { super.onCreateOptionsMenu(menu, inflater) inflater.inflate(R.menu.menu_ingame, menu) }

24. Menu Handlers: Java
public boolean onOptionsItemSelected(MenuItem item) { Activity activity = getActivity(); if (activity != null) {
switch (item.getItemId()) { case R.id.menu_settings:
startActivity(new Intent(activity,
SettingsActivity.class)); return true; case R.id.menu_help: startActivity(new Intent(activity, HelpActivity.class)); return true; case R.id.menu_exit: showQuitAppDialog(); return true; case R.id.menu_contacts: startActivity(new Intent(activity,
ContactsActivity.class)); return true; }
} return false; }

25. Menu Handlers: Kotlin Kotlin’s !! operator asserts that
override fun onOptionsItemSelected(item: MenuItem?): Boolean { when (item!!.itemId) { R.id.menu_settings -> { startActivity(Intent(activity?.applicationContext, SettingsActivity::class.java)) return true } R.id.menu_help -> { startActivity(Intent(activity?.applicationContext, HelpActivity::class.java)) return true } R.id.menu_exit -> { showQuitAppDialog() return true } R.id.menu_contacts -> { startActivity(Intent(activity?.applicationContext, ContactsActivity::class.java)) return true } } return false }
Kotlin’s !! operator asserts that
calling object is not null

26. UI for Larger Screens - Fragments
In Android 3.0 and up with compatibility library (ACL) for earlier versions
Further decouples UI interactions from activity lifecycle
Standard concept in frameworks
Allows reuse of UI components
Specialized activity class – FragmentActivity
We will cover it in a later class

27. Special Types of Activities: Preferences: Java
public class SettingsActivity extends AppCompatActivity { protected Fragment createFragment() { return new SettingsFragment(); } . . protected void onCreate(Bundle savedInstanceState) { FragmentManager fm = getSupportFragmentManager(); Fragment fragment = fm.findFragmentById(R.id.fragment_container); Fragment preferenceFragment = createFragment(); fm.beginTransaction().replace(R.id.fragment_container, preferenceFragment) .commit(); PreferenceManager.setDefaultValues(this, R.xml.settings, false); } } public class SettingsFragment extends PreferenceFragmentCompat { . . public void onCreatePreferences(Bundle savedInstanceState, String rootKey) { // Load preferences from XML resource. addPreferencesFromResource(R.xml.settings); } }
Ask students to view Settings class
Ask students to view settings.xml in layouts
Ask students to see onCreate method
And see:
private final static String OPT_NAME = "name";
private final static String OPT_NAME_DEF = "Player";
private final static String OPT_PLAY_FIRST = "human_starts";
private final static boolean OPT_PLAY_FIRST_DEF = true;

28. Special Types of Activities: Preferences: Kotlin
class SettingsActivity : AppCompatActivity() { protected fun createFragment(): Fragment { return SettingsFragment() } override fun onCreate(savedInstanceState: Bundle?) { val fm = supportFragmentManager val fragment = fm.findFragmentById(R.id.fragment_container) val preferenceFragment = createFragment() fm.beginTransaction().replace(R.id.fragment_container, preferenceFragment) .commit() } PreferenceManager.setDefaultValues(this, R.xml.settings, false) } } class SettingsFragment : PreferenceFragmentCompat() { override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) { // Load preferences from XML resource. addPreferencesFromResource(R.xml.settings) } }

29. Layout File for a Preferences Activity
<?xml version="1.0" encoding="utf-8"?> <PreferenceScreen xmlns:android= android:title="Settings" <EditTextPreference android:key="name" android:title="Player Info" android:summary="Select your name" android:defaultValue="Player 1"/> <CheckBoxPreference android:key="human_starts" android:title="Human Plays First" android:summary="Check box to play first" android:defaultValue="true" /> </PreferenceScreen>

30. Settings
Java
Kotlin
// Settings.java public class Settings { public static String getName( Context context) { return PreferenceManager .getDefaultSharedPreferences(context) .getString(OPT_NAME, OPT_NAME_DEF); } public static boolean doesHumanPlayFirst( Context context) { return PreferenceManager .getDefaultSharedPreferences(context) .getBoolean(OPT_PLAY_FIRST, OPT_PLAY_FIRST_DEF); } }
// Settings.kt object Settings { fun getName(context: Context): String { return PreferenceManager .getDefaultSharedPreferences(context) .getString(OPT_NAME, OPT_NAME_DEF) } fun doesHumanPlayFirst(context: Context): Boolean { return PreferenceManager .getDefaultSharedPreferences(context) .getBoolean(OPT_PLAY_FIRST, OPT_PLAY_FIRST_DEF) } }

31. Questions and comments?
Thank You
Questions and comments?