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2 Adapter An Adapter object acts as a bridge between an AdapterView and the underlying data for that view The Adapter provides access to the data items The Adapter is also responsible for making a View for each item in the data set Adapters provide a common interface to the data model behind a selection-style widget, such as a listbox, spinner etc 2

3 Use of Adapter Android's adapters are responsible for providing the roster of data for widgets/views plus converting individual elements of data into specific views to be displayed inside the widget/views The adapter is assigned to the View via the setadapter method on the View object. An adapter extend the BaseAdapter class. Android provides some standard adapters. The most important are ArrayAdapter and CursorAdapter. 3

4 Types of Adapters Base Adapter ArrayAdapter SimpleAdapter CursorAdapter SimpleCursorAdapter 4

5 BaseAdapter is an abstract base class for the Adapter interface to simplify implementing adapters You could implement your own, but the framework provides some pretty flexible adapters already 5

6 Array Adapter Binds an array of data to a view override getview() to inflate, populate, and return a custom view for the given index in the array. The getview() method includes an opportunity to reuse views via the convertview parameter. 6

7 Using ArrayAdapter The ArrayAdapter can handle Java array or java.util.list as input eg String[] items={"this", "is", "a","really", "silly", "list"}; new ArrayAdapter<String>(this, android.r.layout.simple_list_item_1, items); 7

8 ArrayAdapter constructor takes three parameters: The Context to use (typically this will be your activity instance) The resource ID of a view to use (such as a built-in system resource ID, as shown above) The actual array or list of items to use 8

9 Backing the list as an ArrayList of Maps Each entry in ArrayList corresponds to an row The Maps contains the data for each column 9

put("title", "title"); hm.put("context", "context"); listdata.

10 ArrayList<HashMap<String,Object>> listdata=new ArrayList<HashMap<String,Object>>(); for (int i=0;i<3;i++) { HashMap<String, Object> hm = new HashMap<String, Object>(); hm.put("title", "title"); hm.put("context", "context"); listdata.add(hm); } String[] from = {"title", "context"}; int[] to={r.id.title,r.id.context}; SimpleAdapter adapter = new SimpleAdapter(this, listdata, R.layout.list_item, from, to); 10

11 Cursor Adapter Binds data from a cursor (like a database cursor) to a view Abstract so you don't use it directly, use a subclass or derive your own Implement the abstract method newview() to inflate, populate, and return the desired view for the current cursor position Implement the abstract method bindview() to populate an existing view that is being reused 11

12 Simple Cursor Adapter Concrete implementation of CursorAdapter It can take a row layout and a mapping of cursor columns to row layout widgets Supports text and images, but can customize using setviewtext and setviewimage Can support other types and can customize bindings through a hook 12

13 An adapter needs to know the following in its constructor //the context in which it will operate (required) //the source data (required) //the list item layout (required) //the target fields -- if more than one. //cursor if this is a cursoradapter //you must then set the adapter to the Target View 13

14 Adapter View: Class Diagram 14

15 AdapterView An AdapterView is a view whose children are determined by an Adapter. Commonly used subclasses of Adapterview are as follows: Spinner ListView Gallery Grid View 15

16 Spinner In Android, the Spinner is the equivalent of the drop-down selector you might find in other toolkits (e.g., JComboBox in Java/Swing) Spinners provide a quick way to select one value from a set. In the default state, a spinner shows its currently selected value You can add a spinner to your layout with the Spinner object. You should usually do so in your XML layout with a <Spinner> element. 16

17 Spinner In Android, the Spinner is the equivalent of the drop-down selector you might find in other toolkits (e.g., JComboBox in Java/Swing) Spinners provide a quick way to select one value from a set. In the default state, a spinner shows its currently selected value You can add a spinner to your layout with the Spinner object. You should usually do so in your XML layout with a <Spinner> element. 17

18 Spinner : Choices population Using XML android:entries (Reference to an array resource) Invoke setadapter to add Choices in spinner. The data may come either from ArrayAdapter, if choices are available in array or from Cursor Adapter, if choices are available in database 18

19 Spinner : Selection When the user selects an item from the dropdown, the Spinner object receives an on-itemselected event and its interface implementation be specified by calling setonitemselectedlistener() To define the selection event handler for a spinner, implement the AdapterView.OnItemSelectedListener interface. This interface requires the onitemselected() and onnothingselected() callback methods 19

20 <LinearLayout xmlns:android=" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content"/> <Spinner android:layout_width="fill_parent" android:layout_height="wrap_content" android:drawselectorontop="true"/> </LinearLayout> 20

21 public class SpinnerDemo extends Activity implements AdapterView.OnItemSelectedListener { TextView selection; String[] items= { Table, Chair, Laptop, Mobile, Desktop, File public void oncreate(bundle icicle) { super.oncreate(icicle); setcontentview(r.layout.main); selection=(textview)findviewbyid(r.id.selection); Spinner spin=(spinner)findviewbyid(r.id.spinner); spin.setonitemselectedlistener(this); ArrayAdapter<String> aa=new ArrayAdapter<String>(this, android.r.layout.simple_list_item_1, items); 21

22 aa.setdropdownviewresource( android.r.layout.simple_spinner_dropdown_item); spin.setadapter(aa); } public void onitemselected(adapterview parent, View v, int position, long id) { selection.settext(items[position]); } public void onnothingselected(adapterview parent) { selection.settext(""); } } 22

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25 ListView The classic listbox widget in Android is known as ListView. Following need to be implemented for listview Include listview in your layout Invoke setadapter() to supply data and child views Attach a listener via setonitemselectedlistener() to find out when the selection has been made 25

26 If activity is dominated by a single list, you might consider creating your activity as a subclass of ListActivity, rather than the regular Activity base class. If main view is just the list, you do not even need to supply a layout ListActivity will construct a full-screen list for you. If you do want to customize the layout, you can, so long as you identify your ListView so ListActivity knows which widget is the main list for the activity 26

27 With ListActivity, you can set the list adapter via setlistadapter() in this case, providing an ArrayAdapter wrapping an array of nonsense strings. To find out when the list selection changes, override onlistitemclick() and take appropriate steps based on the supplied child view and position (in this case, updating the label with the text for that position). 27

28 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content"/> <ListView android:layout_width="fill_parent" android:layout_height="fill_parent" android:drawselectorontop="false" /> </LinearLayout> 28

29 public class ListViewDemo extends ListActivity { TextView selection; String[] items= { NeetiKhand", GyanKhand", Shakti Khand", Nyay Khand", Ahinsa Khand", Vaibhav Khand",}; 29

30 @Override public void oncreate(bundle icicle) { super.oncreate(icicle); setcontentview(r.layout.main); Listview List=(ListView)findViewById(R.id.list); setlistadapter(new ArrayAdapter<String>(this, android.r.layout.simple_list_item_1, items)); selection=(textview) findviewbyid(r.id.selection); } public void onlistitemclick(listview parent, View v, int position,long id) { selection.settext(items[position]); } } 30

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32 Custom Adapter & List View Design layout XML file, which will represent one row in the ListView Extend the Adapter class Implement constructor to pass data to sub class Override getview method to map each row with data elements 32

33 Custom Adapter & List public int getcount() { return topic_qcount.length; public Object getitem(int position) { return position; public long getitemid(int position) { return position; public View getview(final int position, View convertview, ViewGroup parent) { } 33

34 Recycle View & Card View 34

35 To create complex lists and cards with material design styles in your apps, you can use the RecyclerView andcardview widgets. The RecyclerView widget is a more advanced and flexible version of ListView. This widget is a container for displaying large data sets that can be scrolled very efficiently by maintaining a limited number of views. Use the RecyclerViewwidget when you have data collections whose elements change at runtime based on user action or network events. To use the RecyclerView widget, you have to specify an adapter and a layout manager. To create an adapter, extend the RecyclerView.Adapter class. 35

36 RecyclerView provides these built-in layout managers: LinearLayoutManager shows items in a vertical or horizontal scrolling list. GridLayoutManager shows items in a grid. StaggeredGridLayoutManager shows items in a staggered grid. To create a custom layout manager, extend therecyclerview.layoutmanager class. 36

37 To create Recycle View do following steps. You need to import appcompat_v7 library if it is not important by default. 1. Create xml file and add v7.widget.recycleview. 2. Create Main Activity Class & create Custom Adapter Class. 3. Create MyAdapter class & extends RecyclerView.Adapter <MyAdapter.ViewHolder> 4. Create Item Class to show the data in Recycle View. 37

38 Create a xml file and add RecycleView. 38

39 <RelativeLayout xmlns:android=" xmlns:tools=" android:layout_width="fill_parent" android:layout_height="match_parent > <android.support.v7.widget.recyclerview xmlns:android=" xmlns:tools=" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".mainactivity" /> </RelativeLayout> 39

40 Create a xml file for item layout 40

41 <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android=" pk/res/android" android:layout_width="fill_parent" android:layout_height="80dp" >  <ImageView android:layout_width="64dp" android:layout_height="64dp" android:layout_alignparentleft="true" android:layout_marginleft="8dp" android:layout_marginright="8dp" android:layout_margintop="1dp" android:layout_marginbottom="1dp" android:contentdescription="icon android: />  <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" " con" gray" android:layout_marginleft="8dp" android:layout_marginright="8dp" android:layout_margintop="8dp" android:textsize="22dp" /> </RelativeLayout> 41

42 Create Main Activity Class 42

43 public class MainActivity extends Activity protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); // 1. get a reference to recyclerview RecyclerView recyclerview = (RecyclerView) findviewbyid(r.id.recyclerview); // this is data fro recycler view ItemData itemsdata[] = { new ItemData("Help",R.drawable.help), new ItemData("Delete",R.drawable.content_discard), new ItemData("Cloud",R.drawable.collections_cloud), new ItemData("Favorite",R.drawable.rating_favorite), new ItemData("Like",R.drawable.rating_good), new ItemData("Rating",R.drawable.rating_important)}; // 2. set layoutmanger recyclerview.setlayoutmanager(new LinearLayoutManager(this)); // 3. create an adapter MyAdapter madapter = new MyAdapter(itemsData); // 4. set adapter recyclerview.setadapter(madapter); // 5. set item animator to DefaultAnimator recyclerview.setitemanimator(new DefaultItemAnimator()); } } 43

44 Create MyAdapter Class & extends RecyclerView.Adapter <MyAdapter. ViewHolder> 44

45 public class MyAdapter extends RecyclerView.Adapter <MyAdapter.ViewHolder> { private ItemData [] itemsdata; public MyAdapter (ItemData[] itemsdata) { this.itemsdata = itemsdata; } // Create new views (invoked by the layout public MyAdapter. ViewHolder oncreateviewholder (ViewGroup parent, int viewtype) { // create a new view View itemlayoutview = LayoutInflater.from (parent.getcontext()).inflate(r.layout.item_layout, null); // create ViewHolder ViewHolder viewholder = new ViewHolder(itemLayoutView); return viewholder; 45

46 } // Replace the contents of a view (invoked by the layout public void onbindviewholder (ViewHolder viewholder, int position) { // - get data from your itemsdata at this position // - replace the contents of the view with that itemsdata } viewholder.txtviewtitle.settext(itemsdata[position].gettitle()); viewholder.imgviewicon.setimageresource(itemsdata[position].getimageurl()); // inner class to hold a reference to each item of RecyclerView public static class ViewHolder extends RecyclerView.ViewHolder { public TextView txtviewtitle; public ImageView imgviewicon; 46

47 } public ViewHolder(View itemlayoutview) { super(itemlayoutview); txtviewtitle = (TextView) itemlayoutview.findviewbyid(r.id.item_title); imgviewicon = (ImageView) itemlayoutview.findviewbyid(r.id.item_icon); } } // Return the size of your itemsdata (invoked by the layout public int getitemcount() { return itemsdata.length; } 47

48 Create a class Item 48

49 public class ItemData { private String title; private int imageurl; public ItemData(String title,int imageurl){ } this.title = title; this.imageurl = imageurl; } // getters & setters 49

50 Run 50

05. RecyclerView and Styles

05. RecyclerView and Styles 08.03.2018 1 Agenda Intents Creating Lists with RecyclerView Creating Cards with CardView Application Bar Menu Styles and Themes 2 Intents 3 What is Intent? An Intent is an