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MDAD 4 - Android - Basics of UI Applications
- 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 2
- 3. Let’s recap • Android – OS – Platform – Kernel – User space libraries – Dalvik / ART – Android Libraries – Applications • Android Applications – Types – Security 3
- 4. Contents • Task • Manifest • Context • Activity – Life cycle – Activity types – Components • Containers • Resources • Build GUI with XML • Toast 4
- 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 6
- 7. 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 7
- 8. Manifest AndroidManifest.xml – Declare components (Activities, Services, etc) – Declare permissions 8
- 9. Context • Context – Any application component • Activities • Services • Content Providers • Broadcast Receivers – Generated by Dalvik/ART • At startup • Provided as a parameter 9
- 10. Context • Abstract Class – Extended by • Activity • Service • ContentProvider • … • Advantages – Avoids static class • Disadvantage – Has to be provided as parameter 10
- 11. Activity • One Window – Uses all the screen (usually) • Contains – Title – One component – One menu • Activated by the menu (soft) button • Extends Activity 11
- 13. 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 (…); – … 13
- 14. Acitivity • Window • Survives the process – Serialising – Partially controlled by the programmer • Not for heavy processing 14
- 15. Storing and loading of the status • Store – void onSaveInstanceState (Bundle state) • Load – void onLoadInstanceState (Bundle state) – void onCreate (Bundle savedInstance) 15
- 16. Starting of an activity • context.startActivity (Intent intent); Intent starter = new Intent (context, ActivityClass.class); context.startActivity (starter); 16
- 17. 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); 17
- 18. Components (Widgets) • Extend View • Placed on an Activity – Static • TextView • ProgressBar • ImageView • … – Dynamic • Button • EditText • CheckBox • RadioButton • SeekBar • Spinner • Gallery • MapView • ListView • … 18
- 21. Container • View – Contains other Views – Layout • Types – LinearLayout – RelativeLayout – TableLayout – ScrollLayout • They are used combined 21
- 24. Resources • res folder (from the source) • Images – drawable -_dpi • ldpi • mdpi • hdpi • UI – layout • Constants – Values • strings.xml • Raw – Unmodifiable resources 24
- 25. 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 25
- 26. Automatic resources in XML • Drawable – Images – @drawable/name • @drawable/icon • @drawable/img1 • @drawable/img2 • Layout – Containers – @layout/name • @layout/main • @layout/people 26
- 27. Constructing the GUI with XML • Complex component • Simple code • No Java code • In the Activity code – this.setContentView (R.layout.name); 27
- 28. GUI XML example file 28
- 29. 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 29
- 30. 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 30
- 31. 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 31
- 32. GUI XML example file XML Java Code 32
- 33. Menu • MENU (soft) button press • Events – public boolean onCreateOptionsMenu (Menu menu); – public boolean onOptionsItemSelected(MenuItem item); • Adding a menu – menu.add (…); 33
- 34. Menu Example 34
- 35. Menu using XML XML (res/menu/meniu.xml) Java Code 35
- 36. Menu using XML • XML (res/menu/meniu.xml) 36
- 37. Menu using XML • Java Code 37
- 38. Toast • Display notifications – Short • Toast.LENGTH_SHORT – Long • Toast.LENGTH_LONG • Toast 38
- 39. Conclusions • Task – A stack of activities • Manifest – Declare activities • Activities – Android Windows – Survive the process – Displays one single component • Use containers – LinearLayout, RelativeLayout, TableLayout • Automatic Resources – Drawable • R.drawable.nume • @/drawable/nume – Layout • Fișiere XML • R.layout.nume • @/layout/nume • Toast – Display messages 39
- 40. 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 40
- 41. Quenstions 41