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1 • Array • ArrayList • Cursor • Spinner • ListView • RecylcerView
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• Array• ArrayList• Cursor
• Spinner• ListView• RecylcerView
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
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• 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 ArrayAdapterand CursorAdapter.
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Use of Adapter
Types of Adapters
• Base Adapter
– ArrayAdapter
– SimpleAdapter
– CursorAdapter
• SimpleCursorAdapter
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• 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
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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.
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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);
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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
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• Backing the list as an ArrayList of Maps
• Each entry in ArrayList corresponds to an row
• The Maps contains the data for each column
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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);
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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
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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
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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
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Adapter View: Class Diagram
AdapterView
• An AdapterView is a view whose children are determined by an Adapter. Commonly used subclasses of Adapterview are as follows:
– Spinner
– ListView
– RecyclerView
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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.
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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.
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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
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Spinner : Selection
• When the user selects an item from the drop-down, the Spinner object receives an on-item-selected 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
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<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="fill_parent"android:layout_height="fill_parent” >
<TextViewandroid:id="@+id/selection"android:layout_width="fill_parent"android:layout_height="wrap_content"/>
<Spinner android:id="@+id/spinner"android:layout_width="fill_parent"android:layout_height="wrap_content"android:drawSelectorOnTop="true"/></LinearLayout>
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public class SpinnerDemo extends Activityimplements AdapterView.OnItemSelectedListener {TextView selection;String[] items= {“Table“, “Chair”, “Laptop”, “Mobile”, “Desktop”,”File”};
@Overridepublic 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);
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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("");}
}
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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
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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
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Custom Adapter & List View
• @Override• public int getCount() {
• return topic_qcount.length;• }
• @Override• public Object getItem(int position) {
• return position;• }
• @Override• public long getItemId(int position) {
• return position;• }
• @Override• public View getView(final int position, View convertView, ViewGroup parent) {
• }
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Recycle View & Card View
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• To create complex lists and cards with material design styles in yourapps, you can use the RecyclerView and CardView widgets.
• The RecyclerView widget is a more advanced and flexible versionof ListView. This widget is a container for displaying large data setsthat can be scrolled very efficiently by maintaining a limited numberof views.
• Use the RecyclerViewwidget when you have data collections whoseelements change at runtime based on user action or network events.
• To use the RecyclerView widget, you have to specify an adapter and alayout manager. To create an adapter, extendthe RecyclerView.Adapter class.
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Recycle View
• 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.
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Recycle View
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. To feed data to RecyleView, create Custom Adapter class MyAdapter thatextends RecyclerView.Adapter <MyAdapter.ViewHolder>
3. Now in activity, need to get handle of RecycleView object, connect it to alayout manager, and attach an adapter for the data to be displayed:
4. Create Item Class to show the data in Recycle View.
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Recycle View
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.
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Recycle View
Create a xml file and add RecycleView.
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="match_parent“>
<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
/>
</RelativeLayout>
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Create a xml file for item layout
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<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="80dp"
android:background="@drawable/border"
>
<!-- icon -->
<ImageView
android:id="@+id/item_icon"
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:src="@drawable/ic_launcher"
/>
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<!-- title --><TextView
android:id="@+id/item_title"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_toRightOf="@+id/item_icon
"android:layout_alignBaseline="@+id/item_i
con"android:textColor="@android:color/darker_
gray"android:layout_marginLeft="8dp"android:layout_marginRight="8dp"android:layout_marginTop="8dp"android:textSize="22dp" />
</RelativeLayout>
Create Main Activity Class
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public class MainActivity extends Activity {
@Overrideprotected 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 viewItemData 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 layoutMangerrecyclerView.setLayoutManager(new LinearLayoutManager(this));// 3. create an adapter MyAdapter mAdapter = new MyAdapter(itemsData);// 4. set adapterrecyclerView.setAdapter(mAdapter);// 5. set item animator to DefaultAnimatorrecyclerView.setItemAnimator(new DefaultItemAnimator());
}}
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Create MyAdapter Class & extends RecyclerView.Adapter <MyAdapter .
ViewHolder>
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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 manager)
@Override
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;
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}
// Replace the contents of a view (invoked by the layout manager)
@Override
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;
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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 manager)
@Override
public int getItemCount() {
return itemsData.length;
}
}
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Create a class Item
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public class ItemData {
private String title;
private int imageUrl;
public ItemData(String title,int imageUrl){
this.title = title;
this.imageUrl = imageUrl;
}
// getters & setters
}
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Run
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