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MDAD 4 - Lists, adapters and recycling
- 1. Android Lists, adapters and recycling
- 2. Bibliography 1. Wallace Jackson, Android Apps for Absolute Beginners, Apress, 2017 2. Hello Views, http://developer.android.com/guide/tutorials/vi ews/index.html 3. Android Application Fundamentals, http://developer.android.com/guide/topics/fun damentals.html 2
- 3. Contents • MVC • Lists – Model – Adaptor • List Elements – Simple – from XML • ListActvity • Optimization – Recycling – Tags – Cache • GridView 3
- 4. Model View Controller • Pattern • Splits – UI – Program – Data storage • Advantages – Programing with components – Easier to maintain • Disadvantages – May be slow 4
- 5. MVC Empirical Database (Model) Display (View) Program logic (Controller) 5
- 7. Specific Activities • ListActivity – Specially for a list – May have other components – List ID • android:id=“@android:id/list” • Special functions – onListItemClick (…) – setListAdapter (…) 7
- 8. Adapter 8
- 9. ListView • A vertical container – Similar with ScrollView – Optimized for movement • Identical components – Each row – Almost true ;) • Adapter’s role – Creates these components • Events – setOnItemClickListener (…) – setOnItemLongClickListener (…) 9
- 10. Adapter • Part of View • Specifies the way of display – Adapts the data – Modifies the View 10
- 11. ListView Adapter • Predefined – ArrayAdapter • User defined – Implementation of ListAdapter – Extend BaseAdapter 11
- 12. Usage of ArrayAdapter (XML) • Example – Static list 12
- 13. Usage of ArrayAdapter (Java) • Example – Static List 13
- 14. Usage of ArrayAdapter (XML) • Example – Dynamic List 14
- 15. Usage of ArrayAdapter (Java) 15
- 16. A simple list • ListView – Contains a list – android:id=“@android:id/list” • Elements of the list – android.R.layout.simple_list_item_1 • Static – May use String[] • Dynamic – Use ArrayList<String> 16
- 17. The List with complex elements • Elements – Components • EditView • ImageView • Container • Adapter custom-made – Implement ListAdapter – Extend BaseAdapter 17
- 18. Extend BaseAdapter • View getView (int position, View convertView, ViewGroup list) • int getCount () • Object getItem (int position) • long getItemId (int position) • int getViewTypeCount () • int getItemViewType (int position) 18
- 24. Recycling • Objects reusage • Avoid object creation – new is bad for memory! • Use – Buffers – Lists 24
- 27. Different types of elements? int getViewTypeCount () int getItemViewType (int position) 27
- 29. Tags (for View) • void setTag (Object tag) • Object getTag () 29
- 30. Efficient using Tag Utilizarea tag-ului 30
- 31. GridView • Identical with ListView – Extend BaseAdapater 31
- 32. The new RecyclerView • A new way of building lists – Uses several layouts • Not just a LinearLayout – The developer has to use recycling and tagging • Extend RecyclerView.Adapter – onCreateViewHolder() • Inflate the view – onBindViewHolder() • Set the View’s data – getItemCount() 32
- 33. Conclusions • Lists – Linear containers – Contain components • Including containers • ListActivity – Activity with special functions for list • Adapter – Formats the data from the model for the list – Simple – Custom made – Recycling of elements • Elements – Described in XML 33
- 34. Keywords • MVC • Adaptor • Classes – ListActivity – ListView – GridView – View – ArrayAdapter – BaseAdapter – ArrayList • Interfaces – ListAdapter • Recycling • Tags 34
- 35. Questions 35