1. Android
Basics of UI Applications

2. Bibliography
1. Wallace Jackson, Android Apps for Absolute
Beginners, Apress, 2017
2. Peter Späth, Learn Kotlin for Android
Development, Apress 2019
3. Android Application Fundamentals,
http://developer.android.com/guide/topics/f
undamentals.html
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3. Let’s recap
• Android
– OS
– Platform
– Kernel
– User space libraries
– Hardware Abstraction
Layer
– Dalvik / ART
– Android Libraries
– Applications
• Android Applications
– Types
– Security
3

4. Contents
• Containers
• Resources
• Build GUI with XML
• Intents
• Manifest
• Toast
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5. Android Schematics
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6. Task (UI Application)
• Runs in one process
– usually!
– There are exceptions
• Stack of activities
• Root activity
– Add
• Display
• push
– Remove
• Hide
• pop
– Activities from other
applications
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7. Important Functions
• Clasa Activity
– void onCreate (…);
– void onStart (…);
– void onRestart (…);
– void onResume (…);
– void onPause (…);
– void onStop (…);
– void onDestroy (…);
• Must call the parent
overridden functions
• super.onCreate (…);
– …
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8. Storing and loading of the status
• Store
– void onSaveInstanceState (Bundle state)
• Load
– void onLoadInstanceState (Bundle state)
– void onCreate (Bundle savedInstance)
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9. Components (Widgets)
• Extend View
• Placed on an Activity
– Static
• TextView
• ProgressBar
• ImageView
• …
– Dynamic
• Button
• EditText
• CheckBox
• RadioButton
• SeekBar
• Spinner
• Gallery
• MapView
• ListView
• …
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10. Container
• View
– Contains other Views
– Layout
• Types (outdated)
– LinearLayout
– RelativeLayout
– TableLayout
– ScrollLayout
• They are used
combined
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11. Container Types
LinearLayout RelativeLayout
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12. Container Types
TableLayout AbsoluteLayout
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13. Resources
• res folder (from the source)
• Images
– drawable -_dpi
• ldpi
• mdpi
• hdpi
• UI
– layout
• Constants
– Values
• strings.xml
• Raw
– Unmodifiable resources
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14. Automatic resources in Java code
• Drawable
– Images
– R.drawable.name
• R.drawable.icon
• R.drawable.img1
• R.drawable.img2
• Layout
– Containers
– R.layout.name
• R.layout.main
• R.layout.people
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15. Automatic resources in XML
• Drawable
– Images
– @drawable/name
• @drawable/icon
• @drawable/img1
• @drawable/img2
• Layout
– Containers
– @layout/name
• @layout/main
• @layout/people
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16. Constructing the GUI with XML
• Complex component
• Simple code
• No Java code
• In the Activity code
– this.setContentView (R.layout.name);
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17. GUI XML example file
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18. GUI XML example file
• xmlns:android
– Only the root component
– mandatory
• android:layout_width
• android:layout_height
– mandatory
– Values
• fill_parent
• wrap_content
• match_parent
• n px
• n cm
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19. GUI XML example file
• android:id
– Usage of the component
in the Java code
– @+id/name
• R.id.name
– Example
• @+id/button1
– R.id.button1
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20. GUI XML example file
• android:id
– Usage of the component
in the Java code
– @+id/name
• R.id.name
– Example
• @+id/button1
– R.id.button1
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21. GUI XML example file
XML Java Code
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22. Menu
• MENU (soft) button press
• Events
– public boolean
onCreateOptionsMenu (Menu
menu);
– public boolean
onOptionsItemSelected(MenuItem
item);
• Adding a menu
– menu.add (…);
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23. Menu Example
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24. Menu using XML
XML (res/menu/meniu.xml) Java Code
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25. Menu using XML
• XML (res/menu/meniu.xml)
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26. Menu using XML
• Java Code
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27. Intents
• Intent
– A component that wants
something
• Generates events
– Phone call
– Send sms
• Object
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28. The intent is described by
• Action
• Data
• Category
• Type
• Component
• Extras
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29. Action
• Desired action
– Call
– Send sms
– Open document
– Edit document
– Start an activity
• String
– “android.intent.action.MAIN”
– “android.intent.action.VIEW”
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30. Action example
• ACTION_MAIN
• ACTION_VIEW
• ACTION_EDIT
• ACTION_PICK
• ACTION_CHOOSER
• ACTION_GET_CONTENT
• ACTION_DIAL
• ACTION_CALL
• ACTION_SEND
• ACTION_SENDTO
• ACTION_ANSWER
• ACTION_SEARCH
• ACTION_WEB_SEARCH
• …
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31. Exampe of informative action
• ACTION_TIME_TICK
• ACTION_TIME_CHANGED
• ACTION_TIMEZONE_CHANGED
• ACTION_BOOT_COMPLETED
• ACTION_PACKAGE_ADDED
• ACTION_PACKAGE_CHANGED
• ACTION_PACKAGE_REMOVED
• ACTION_PACKAGE_RESTARTED
• ACTION_PACKAGE_DATA_CLEARED
• ACTION_UID_REMOVED
• ACTION_BATTERY_CHANGED
• ACTION_POWER_CONNECTED
• ACTION_POWER_DISCONNECTED
• ACTION_SHUTDOWN
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32. Data
• Associated data
• Usually an URI
– tel:123
– content://contacts/…
– File:///sdcard/...
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33. Category
• Defines better the action
– CATEGORY_LAUNCHER
– CATEGORY_ALTERNATIVE
– CATEGORY_DEFAULT
• Additional information
• Optional
• String
– "android.intent.category.MAIN“
– "android.intent.category.ALTERNATIVE"
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34. Category example
• CATEGORY_DEFAULT
• CATEGORY_BROWSABLE
• CATEGORY_TAB
• CATEGORY_ALTERNATIVE
• CATEGORY_SELECTED_ALTERNATIVE
• CATEGORY_LAUNCHER
• CATEGORY_INFO
• CATEGORY_HOME
• CATEGORY_PREFERENCE
• CATEGORY_TEST
• CATEGORY_CAR_DOCK
• CATEGORY_DESK_DOCK
• CATEGORY_CAR_MODE
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35. Type
• Data type
– It is generally determined in
• file:///sdcard/poze/poza.jpg
– It has priority over
• Optional
• String
– “image/jpg”
– “contacts/contact”
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36. Component
• Mentions the specific
destination component
• Optional
• Start/Stop
– Activities
• startActivity (…)
• finishActivity (…)
– Services
• startService (…)
• stopService (…)
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37. Extras
• Extra data
• Bundle
– putExtra ()
– getStringExtra ()
– getIntExtra ()
– getBooleanExtra ()
– …
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38. Usage
• Functions which emit intents
– void startActivity (Intent i)
– void startService (Intent i)
– void sendBroadcast (Intent i, String permission)
• The system searches for the appropriate
component
– Intent Resolution
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39. Search for the activity
• Filter arguments
– ACTION
– TYPE (usually extracted from DATA)
– CATEGORY
• Determined
– Determines the appropriate component
– Determines the appropriate components list
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40. IntentFilters
• Components that declare filters
– Activities
– Services
– BoradcastReceivers
• Windows equivalent
– File association
• In AndroidManifest.xml
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41. Example
The applications menu asks for a list of components that respond to
Action: ACTION_MAIN
Category: CATEGORY_LAUNCHER
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42. Exemple (2)
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43. Exemple (3)
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44. Manifest
AndroidManifest.xml
– Declare components (Activities, Services, etc)
– Declare permissions
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45. Starting of an activity
• context.startActivity (Intent intent);
Intent starter = new Intent (context,
ActivityClass.class);
context.startActivity (starter);
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46. Stopping an activity
• context.finishActivity (Intent intent);
– Another component wants to stop the Activity
• finish ();
– The Activity stops itself
Intent starter = new Intent (context,
ActivityClass.class);
Context.finishActivity (starter);
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47. Toast
• Display notifications
– Short
• Toast.LENGTH_SHORT
– Long
• Toast.LENGTH_LONG
• Toast
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48. Conclusions
• Task
– A stack of activities
• Intents
• Manifest
– Declare activities
• Automatic Resources
– Drawable
• R.drawable.nume
• @/drawable/nume
– Layout
• Fișiere XML
• R.layout.nume
• @/layout/nume
• Toast
– Display messages
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49. Keywords
• Task
– Stack
• Activity
– Lifecycle
• Containers
– Layouts
– LinearLayout
– TableLayout
– RelativeLayout
– GridLayout
• Toast
• XML GUI
• Menu
• Manifest
• Components
– Static
• TextView
• ProgressBar
• ImageView
• …
– Dynamic
• Button
• EditText
• CheckBox
• RadioButton
• SeekBar
• Spinner
• Gallery
• MapView
• ListView
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50. Quenstions
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