Android Application Model I

CSE 5236: Mobile Application DevelopmentInstructor: Adam C. Champion, Ph.D.

Course Coordinator: Dr. Rajiv Ramnath

1

Framework Support (e.g. Android)

2

Framework Capabilities and Add-Ons

• Tailored to mobile apps• Built-in services:

– GUI – OS services (file I/O, threads, device management)– Graphics– Device access (GPS, camera, music and video players, sensors)– Web services– Networking– XML processing– Standard language libraries

• Add-ons:– Maps– Database support (SQLite)– WebKit

3

IDE Support

• Eclipse, Android Studio (Beta)• Testing tools (test management, unit

tests)• Performance profiling tools• SCM integration (Git, SVN, CVS)• Software emulators• Sensor injection (GPS, other sensors)

4

Android Studio Project Components

5

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 are composed of Activities – a “cohesive step” in an Android application

6

Activities in Tic-Tac-Toe

7

Specifying Activities – AndroidManifest.xml<activity android:name=".SplashScreen"

android:label="@string/app_name"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:label="@string/app_name"android:launchMode="singleInstance"android:screenOrientation="portrait">

<intent-filter><action

android:name="com.wiley.fordummies.androidsdk.Login"/><category android:name="android.intent.category.DEFAULT"/>

</intent-filter></activity>

8

Implementing Activities

Javapublic class LoginActivityextendsSingleFragmentActivity {......

}...public class GameSessionActivity extendsSingleFragmentActivity {

...

...}

Kotlinclass LoginActivity : SingleFragmentActivity() {......

}...class GameSessionActivity : SingleFragmentActivity() {

...

...}

9Note: SingleFragmentActivity extends FragmentActivity

Activity UI

• Widgets• View and ViewGroup• Package android.view• Specified declaratively in layout

files• Always use Fragments…

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Sample Layout: Login Activity<?xml version="1.0" encoding="utf-8"?><ScrollView xmlns:android="http://schemas.android.com/apk/res/android”

android:background="@color/background"android:orientation="horizontal"android:layout_width="fill_parent"android:layout_height="fill_parent"android:padding="20dip"><LinearLayout android:orientation="vertical. . .

<TextView android:text="@string/login_title” /><TextView . . . /><EditText . . . /><TextView . . . /><EditText . . . /><Button . . . /><Button . . . /><Button . . . />

</LinearLayout></ScrollView>

11<project>/app/src/main/res/layout/fragment_login.xml

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 ressubtree.

12

Implement UI Logic: Listener Objects: Javapublic 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;. . .@Overridepublic View onCreateView(. . .) {

View v = inflater.inflate(R.layout.fragment_login, container, false);

mUsernameEditText = (EditText) v.findViewById(R.id.username_text);mPasswordEditText = (EditText) v.findViewById(R.id.password_text);

Button loginButton = (Button) v.findViewById(R.id.login_button);. . .loginButton.setOnClickListener(this);Button cancelButton = (Button) v.findViewById(R.id.cancel_button);. . .cancelButton.setOnClickListener(this);Button newUserButton = (Button) v.findViewById(R.id.new_user_button);. . .newUserButton.setOnClickListener(this);

return v;}

13

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: EditTextprivate lateinit var mPasswordEditText: EditText. . .override fun onCreateView(. . . ): View? {

val v = inflater.inflate(R.layout.fragment_login, container, false)

mUsernameEditText = v.findViewById<EditText>(R.id.username_text)mPasswordEditText = v.findViewById<EditText>(R.id.password_text)

val loginButton = v.findViewById<Button>(R.id.login_button)loginButton.setOnClickListener(this)val cancelButton = v.findViewById<Button>(R.id.cancel_button) cancelButton.setOnClickListener(this)val newUserButton = v.findViewById<Button>(R.id.new_user_button)newUserButton.setOnClickListener(this)

return v}

. . . } 14

The OnClick Handler

Java public void onClick(View v) {

switch (v.getId()) {case R.id.login_button:

checkLogin();break;

case R.id.cancel_button:finish();break;

case R.id.new_user_button:startActivity(new

Intent(this, Account.class));break;

}}

Kotlinoverride fun onClick(view: View) {

when (view.id) {R.id.login_button ->

checkLogin()R.id.cancel_button ->

activity.finish()R.id.new_user_button ->

startActivity(Intent(activity.applicationContext, AccountActivity::class.java))

}}

15

Embedding a View: GameSessionActivity, Fragment: Java

public class GameSessionActivity extends SingleFragmentActivity {. . .

}

public class GameSessionFragment extends Fragment {. . .

}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android” . . >

<LinearLayout...<com.wiley.fordummies.androidsdk.Board

android:id="@+id/board"android:layout_width="fill_parent"android:layout_height="fill_parent"/>

</LinearLayout><TextView ... "/><TextView ... "/>

</LinearLayout> 16

Embedding a View: GameSessionActivity, Fragment: Kotlin

class GameSessionActivity : SingleFragmentActivity() {

}

class GameSessionFragment : Fragment() {

}

<!-- Same XML as before -->

17

Embedding a View: Board Class

Java// Board.javapublic class Board extends View {

...public boolean onTouchEvent(

MotionEvent event) {. . .switch (action) {

case MotionEvent.ACTION_DOWN:. . .break;

}return super.onTouchEvent(event);}

}

Kotlin// Board.ktclass Board : View {

. . . override fun onTouchEvent(

event: MotionEvent): Boolean {. . . when (action) {

MotionEvent.ACTION_DOWN -> { . . . }

}return super.onTouchEvent(event)

}}

18

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.

19

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.

20

Menu Layout File<?xml version="1.0" encoding="utf-8"?><menu xmlns:android="http://schemas.android.com/apk/res/android">

<item android:title="Settings" android:id="@+id/menu_settings"android:icon="@android:drawable/ic_menu_preferences"

/><item android:title="Help"

android:id="@+id/menu_help"android:icon="@android:drawable/ic_menu_info_details"

/> <item android:title="Exit"

android:id="@+id/menu_exit"android:icon="@android:drawable/ic_menu_close_clear_cancel"

/><item android:title="Contacts"

android:id="@+id/menu_contacts"android:icon="@android:drawable/ic_menu_view"

/></menu>

Action Bar: Declare menu item with additional attribute android:showAsAction ="ifRoom", "never", "withText" or "always".

21

Menu Creation: Javapublic class GameOptionsFragment {

...public View onCreateView(…) {

setHasOptionsMenu(true);}public boolean onCreateOptionsMenu(Menu menu) {

super.onCreateOptionsMenu(menu);MenuInflater inflater = getMenuInflater();inflater.inflate(R.menu.menu, menu);return true;

}...

}

22

Menu Creation: Kotlinclass GameOptionsFragment {

. . .fun onCreateView(…) {

setHasOptionsMenu(true);}. . .fun onCreateOptionsMenu(menu: Menu?,

inflater: MenuInflater?) {super.onCreateOptionsMenu(menu,inflater)inflater!!.inflate(R.menu.menu, menu)

}

23

Menu Handlers: Java

24

public boolean onOptionsItemSelected(MenuItem item) {switch (item.getItemId()) {

case R.id.menu_settings:startActivity(new Intent(getActivity(),SettingsActivity.class));

return true;case R.id.menu_help:

startActivity(new Intent(getActivity(),HelpActivity.class));

return true;case R.id.menu_exit:

showQuitAppDialog();return true;

case R.id.menu_contacts:startActivity(new Intent(getActivity(),ContactsActivity.class));

return true; } return false; }

Menu Handlers: Kotlinfun onOptionsItemSelected(item: MenuItem?): Boolean {

when (item!!.itemId) {R.id.menu_settings -> {

startActivity(Intent(activity, SettingsActivity::class.java))

return true }R.id.menu_help -> {

startActivity(Intent(activity,HelpActivity::class.java))

return true }R.id.menu_exit -> {

showQuitAppDialog()return true }

R.id.menu_contacts -> {startActivity(Intent(activity,ContactsActivity::class.java))

return true }}return false }

25

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

26

Special Types of Activities: Preferences: Javapublic class SettingsActivity extends AppCompatActivity {

. . .protected Fragment createFragment() { return new SettingsFragment(); }. . .@Overrideprotected 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 {

. . .@Overridepublic void onCreatePreferences(Bundle savedInstanceState, String rootKey) {

// Load preferences from XML resource.addPreferencesFromResource(R.xml.settings);

}}

27

Special Types of Activities: Preferences: Kotlinclass SettingsActivity : AppCompatActivity() {

. . . protected fun createFragment(): Fragment { return SettingsFragment() }. . . override fun onCreate(savedInstanceState: Bundle?) {

. . .val fm = supportFragmentManagerval 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)

}

}28

Layout File for a Preferences Activity

<?xml version="1.0" encoding="utf-8"?><PreferenceScreenxmlns:android=http://schemas.android.com/apk/res/android

android:title="Settings"android:background="@color/background">

<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>

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Settings

Java// Settings.javapublic class Settings {

. . .public static String getName(

Context context) {return PreferenceManager

.getDefaultSharedPreferences(context)

.getString(OPT_NAME, OPT_NAME_DEF);}

public static booleandoesHumanPlayFirst(Context context) {

return PreferenceManager.getDefaultSharedPreferences(context).getBoolean(OPT_PLAY_FIRST,

OPT_PLAY_FIRST_DEF);}

}

Kotlin// Settings.ktobject 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)}

}

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Thank You

Questions and comments?

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