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Friday, 16 March 2012

Chapter 16:Constants adapter


Constants

public static final int IGNORE_ITEM_VIEW_TYPE

Since: API Level 1
An item view type that causes the AdapterView to ignore the item view. For example, this can be used if the client does not want a particular view to be given for conversion in getView(int, View, ViewGroup).
See Also
Constant Value: -1 (0xffffffff)

public static final int NO_SELECTION

Since: API Level 1
Constant Value: -2147483648 (0x80000000)

Public Methods

public abstract int getCount ()

Since: API Level 1
How many items are in the data set represented by this Adapter.
Returns
  • Count of items.

public abstract Object getItem (int position)

Since: API Level 1
Get the data item associated with the specified position in the data set.
Parameters
position Position of the item whose data we want within the adapter's data set.
Returns
  • The data at the specified position.

public abstract long getItemId (int position)

Since: API Level 1
Get the row id associated with the specified position in the list.
Parameters
position The position of the item within the adapter's data set whose row id we want.
Returns
  • The id of the item at the specified position.

public abstract int getItemViewType (int position)

Since: API Level 1
Get the type of View that will be created by getView(int, View, ViewGroup) for the specified item.
Parameters
position The position of the item within the adapter's data set whose view type we want.
Returns
See Also

public abstract View getView (int position, View convertView, ViewGroup parent)

Since: API Level 1
Get a View that displays the data at the specified position in the data set. You can either create a View manually or inflate it from an XML layout file. When the View is inflated, the parent View (GridView, ListView...) will apply default layout parameters unless you use inflate(int, android.view.ViewGroup, boolean) to specify a root view and to prevent attachment to the root.
Parameters
position The position of the item within the adapter's data set of the item whose view we want.
convertView The old view to reuse, if possible. Note: You should check that this view is non-null and of an appropriate type before using. If it is not possible to convert this view to display the correct data, this method can create a new view. Heterogeneous lists can specify their number of view types, so that this View is always of the right type (see getViewTypeCount() and getItemViewType(int)).
parent The parent that this view will eventually be attached to
Returns
  • A View corresponding to the data at the specified position.

public abstract int getViewTypeCount ()

Since: API Level 1
Returns the number of types of Views that will be created by getView(int, View, ViewGroup). Each type represents a set of views that can be converted in getView(int, View, ViewGroup). If the adapter always returns the same type of View for all items, this method should return 1.
This method will only be called when when the adapter is set on the the AdapterView.
Returns
  • The number of types of Views that will be created by this adapter

public abstract boolean hasStableIds ()

Since: API Level 1
Indicates whether the item ids are stable across changes to the underlying data.
Returns
  • True if the same id always refers to the same object.

public abstract boolean isEmpty ()

Since: API Level 1
Returns
  • true if this adapter doesn't contain any data. This is used to determine whether the empty view should be displayed. A typical implementation will return getCount() == 0 but since getCount() includes the headers and footers, specialized adapters might want a different behavior.

public abstract void registerDataSetObserver (DataSetObserver observer)

Since: API Level 1
Register an observer that is called when changes happen to the data used by this adapter.
Parameters
observer the object that gets notified when the data set changes.

public abstract void unregisterDataSetObserver (DataSetObserver observer)

Since: API Level 1
Unregister an observer that has previously been registered with this adapter via registerDataSetObserver(DataSetObserver).
Parameters
observer the object to unregister. 



a)
ArrayAdapters





A
concrete BaseAdapter that is backed by an array of arbitrary objects.
By default this class expects that the provided resource id
references a single TextView. If you want to use a more complex
layout, use the constructors that also takes a field id. That field
id should reference a TextView in the larger layout resource. 


However the TextView is referenced, it will be filled with the
toString() of each object in the array. You can add lists or arrays
of custom objects. Override the toString() method of your objects to
determine what text will be displayed for the item in the list. 


To use something other than TextViews for the array display, for
instance, ImageViews, or to have some of data besides toString()
results fill the views, override getView(int,
View, ViewGroup) to return the type of view you want. 





Public Constructors





public ArrayAdapter (Context
context, int textViewResourceId) 


Since: API
Level 1 


Constructor




Parameters



 
 
 


  context 
   
  The current context.
 



  textViewResourceId 
   
  The resource ID for a layout file containing a TextView to use
   when instantiating views. 
   
 







public ArrayAdapter (Context
context, int resource, int textViewResourceId) 


Since: API
Level 1 


Constructor




Parameters



 
 
 


  context 
   
  The current context.
 



  resource 
   
  The resource ID for a layout file containing a layout to use
   when instantiating views.
 



  textViewResourceId 
   
  The id of the TextView within the layout resource to be
   populated 
   
 







public ArrayAdapter (Context
context, int textViewResourceId, T[] objects) 


Since: API
Level 1 


Constructor




Parameters



 
 
 


  context 
   
  The current context.
 



  textViewResourceId 
   
  The resource ID for a layout file containing a TextView to use
   when instantiating views.
 



  objects 
   
  The objects to represent in the ListView. 
   
 







public ArrayAdapter (Context
context, int resource, int textViewResourceId, T[] objects) 


Since: API
Level 1 


Constructor




Parameters



 
 
 


  context 
   
  The current context.
 



  resource 
   
  The resource ID for a layout file containing a layout to use
   when instantiating views.
 



  textViewResourceId 
   
  The id of the TextView within the layout resource to be
   populated
 



  objects 
   
  The objects to represent in the ListView. 
   
 







public ArrayAdapter (Context
context, int textViewResourceId, List<T>
objects) 


Since: API
Level 1 


Constructor




Parameters



 
 
 


  context 
   
  The current context.
 



  textViewResourceId 
   
  The resource ID for a layout file containing a TextView to use
   when instantiating views.
 



  objects 
   
  The objects to represent in the ListView. 
   
 







public ArrayAdapter (Context
context, int resource, int textViewResourceId, List<T>
objects) 


Since: API
Level 1 


Constructor




Parameters



 
 
 


  context 
   
  The current context.
 



  resource 
   
  The resource ID for a layout file containing a layout to use
   when instantiating views.
 



  textViewResourceId 
   
  The id of the TextView within the layout resource to be
   populated
 



  objects 
   
  The objects to represent in the ListView. 
   
 






Public Methods




public void add (T object) 


Since: API
Level 1 


Adds the specified object at the end of the array.




Parameters



 
 
 


  object 
   
  The object to add at the end of the array. 
   
 







public void addAll (Collection<? extends T>
collection) 


Since: API
Level 11 


Adds the specified Collection at the end of the array.




Parameters



 
 
 


  collection 
   
  The Collection to add at the end of the array. 
   
 






public void addAll
(T... items) 


Since: API
Level 11 


Adds the specified items at the end of the array.




Parameters



 
 
 


  items 
   
  The items to add at the end of the array. 
   
 






public void clear () 


Since: API
Level 1 


Remove all elements from the list. 






public static ArrayAdapter<CharSequence>
createFromResource (Context
context, int textArrayResId, int textViewResId) 


Since: API
Level 1 


Creates a new ArrayAdapter from external resources. The content of
the array is obtained through getTextArray(int).




Parameters



 
 
 


  context 
   
  The application's environment.
 



  textArrayResId 
   
  The identifier of the array to use as the data source.
 



  textViewResId 
   
  The identifier of the layout used to create views.
 






Returns


    

  • An ArrayAdapter. 
 
    


    • 





public Context
getContext () 


Since: API
Level 1 


Returns the context associated with this array adapter. The
context is used to create views from the resource passed to the
constructor.




Returns


    

  • The Context associated with this adapter. 
 
    


    • 





public int getCount () 


Since: API
Level 1 






public View
getDropDownView (int position, View
convertView, ViewGroup
parent) 


Since: API
Level 1 


Get a View
that displays in the drop down popup the data at the specified
position in the data set.




Parameters



 
 
 


  position 
   
  index of the item whose view we want.
 



  convertView 
   
  the old view to reuse, if possible. Note: You should check that
   this view is non-null and of an appropriate type before using. If
   it is not possible to convert this view to display the correct
   data, this method can create a new view.
 



  parent 
   
  the parent that this view will eventually be attached to
 






Returns


    

  • a View
 corresponding to the data at the specified position. 
 
    


    • 





public Filter
getFilter () 


Since: API
Level 1 


Returns a filter that can be used to constrain data with a
filtering pattern.

This method is usually implemented by Adapter
classes.




Returns


    

  • a filter used to constrain data 
 
    


    • 





public T getItem (int
position) 


Since: API
Level 1 





public long
getItemId (int position) 


Since: API
Level 1 





public int
getPosition (T item) 


Since: API
Level 1 


Returns the position of the specified item in the array.




Parameters



 
 
 


  item 
   
  The item to retrieve the position of.
 






Returns


    

  • The position of the specified item. 
 
    


    • 






public View
getView (int position, View
convertView, ViewGroup
parent) 


Since: API
Level 1 





public void insert
(T object, int index) 


Since: API
Level 1 


Inserts the specified object at the specified index in the array.




Parameters



 
 
 


  object 
   
  The object to insert into the array.
 



  index 
   
  The index at which the object must be inserted. 
   
 






public void
notifyDataSetChanged () 


Since: API
Level 1 


Notifies the attached observers that the underlying data has been
changed and any View reflecting the data set should refresh itself. 





public void remove (T
object) 


Since: API
Level 1 


Removes the specified object from the array.




Parameters



 
 
 


  object 
   
  The object to remove. 
   
 






public
void setDropDownViewResource (int resource) 


Since: API
Level 1 


Sets the layout resource to create the drop down views.




Parameters



 
 
 


  resource 
   
  the layout resource defining the drop down views
 






See Also





public
void setNotifyOnChange (boolean notifyOnChange) 


Since: API
Level 1 


Control whether methods that change the list (add(T),
insert(T,
int), remove(T),
clear())
automatically call notifyDataSetChanged().
If set to false, caller must manually call notifyDataSetChanged() to
have the changes reflected in the attached view. The default is true,
and calling notifyDataSetChanged() resets the flag to true.




Parameters



 
 
 


  notifyOnChange 
   
  if true, modifications to the list will automatically call
   notifyDataSetChanged()
      
 







public void sort (Comparator<? super T>
comparator) 


Since: API
Level 3 


Sorts the content of this adapter using the specified comparator.




Parameters



 
 
 


  comparator 
   
  The comparator used to sort the objects contained in this
   adapter. 
   
 

















b)
BaseAdapters







Common base class of common implementation for an Adapter
that can be used in both ListView
(by implementing the specialized ListAdapter
interface} and Spinner
(by implementing the specialized SpinnerAdapter
interface. 






Public Constructors



public BaseAdapter ()


Since: API
Level 1 





Public Methods



public boolean
areAllItemsEnabled () 


Since: API
Level 1 



Indicates whether all the items in this adapter are enabled. If
the value returned by this method changes over time, there is no
guarantee it will take effect. If true, it means all items are
selectable and clickable (there is no separator.)




Returns


    

  • True if all items are enabled, false otherwise.
    


    • 





public View
getDropDownView (int position, View
convertView, ViewGroup
parent) 


Since: API
Level 1 



Get a View
that displays in the drop down popup the data at the specified
position in the data set.




Parameters



 
 
 


  
   position 
   


  		
  
   index of the item whose view we want.


  		
 



  
   convertView 
   


  		
  
   the old view to reuse, if possible. Note: You should check that
   this view is non-null and of an appropriate type before using. If
   it is not possible to convert this view to display the correct
   data, this method can create a new view.


  		
 



  
   parent 
   


  		
  
   the parent that this view will eventually be attached to


  		
 





Returns


    

  • a View
 corresponding to the data at the specified position. 
 
    


    • 




public int
getItemViewType (int position) 


Since: API
Level 1 



Get the type of View that will be created by getView(int,
View, ViewGroup) for the specified item.




Parameters



 
 
 


  
   position 
   


  		
  
   The position of the item within the adapter's data set whose
   view type we want.


  		
 





Returns




public int
getViewTypeCount () 


Since: API
Level 1 



Returns the number of types of Views that will be created by
getView(int,
View, ViewGroup). Each type represents a set of views that
can be converted in getView(int,
View, ViewGroup). If the adapter always returns the same
type of View for all items, this method should return 1. 



This method will only be called when when the adapter is set on
the the AdapterView.





Returns


    

  • The number of types of Views that will be created by this
 adapter 
 
    


    • 




public boolean
hasStableIds () 


Since: API
Level 1 



Indicates whether the item ids are stable across changes to the
underlying data.




Returns


    

  • True if the same id always refers to the same object. 
 
    


    • 




public boolean isEmpty
() 


Since: API
Level 1 





public boolean
isEnabled (int position) 


Since: API
Level 1 



Returns true if the item at the specified position is not a
separator. (A separator is a non-selectable, non-clickable item). The
result is unspecified if position is invalid. An
ArrayIndexOutOfBoundsException
should be thrown in that case for fast failure.




Parameters



 
 
 


  
   position 
   


  		
  
   Index of the item


  		
 





Returns


    

  • True if the item is not a separator
    


    • 




public void
notifyDataSetChanged () 


Since: API
Level 1 



Notifies the attached observers that the underlying data has been
changed and any View reflecting the data set should refresh itself. 





public
void notifyDataSetInvalidated () 


Since: API
Level 1 



Notifies the attached observers that the underlying data is no
longer valid or available. Once invoked this adapter is no longer
valid and should not report further data set changes. 






public void registerDataSetObserver (DataSetObserver
observer) 


Since: API
Level 1 



Register an observer that is called when changes happen to the
data used by this adapter.




Parameters



 
 
 


  
   observer 
   


  		
  
   the object that gets notified when the data set changes. 
   


  		
 






public void unregisterDataSetObserver (DataSetObserver
observer) 


Since: API
Level 1 



Unregister an observer that has previously been registered with
this adapter via registerDataSetObserver(DataSetObserver).




Parameters



 
 
 


  
   observer 
   


  		
  
   the object to unregister. 
   


  		
 













































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