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Added in API level 1

ExpandableListActivity

public class ExpandableListActivity
extends Activity implements View.OnCreateContextMenuListener, ExpandableListView.OnChildClickListener, ExpandableListView.OnGroupCollapseListener, ExpandableListView.OnGroupExpandListener

java.lang.Object
   ↳ android.content.Context
     ↳ android.content.ContextWrapper
       ↳ android.view.ContextThemeWrapper
         ↳ android.app.Activity
           ↳ android.app.ExpandableListActivity


An activity that displays an expandable list of items by binding to a data source implementing the ExpandableListAdapter, and exposes event handlers when the user selects an item.

ExpandableListActivity hosts a ExpandableListView object that can be bound to different data sources that provide a two-levels of data (the top-level is group, and below each group are children). Binding, screen layout, and row layout are discussed in the following sections.

Screen Layout

ExpandableListActivity has a default layout that consists of a single, full-screen, centered expandable list. However, if you desire, you can customize the screen layout by setting your own view layout with setContentView() in onCreate(). To do this, your own view MUST contain an ExpandableListView object with the id "@android:id/list" (or list if it's in code)

Optionally, your custom view can contain another view object of any type to display when the list view is empty. This "empty list" notifier must have an id "android:empty". Note that when an empty view is present, the expandable list view will be hidden when there is no data to display.

The following code demonstrates an (ugly) custom screen layout. It has a list with a green background, and an alternate red "no data" message.

 <?xml version="1.0" encoding="UTF-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
         android:orientation="vertical"
         android:layout_width="match_parent" 
         android:layout_height="match_parent"
         android:paddingLeft="8dp"
         android:paddingRight="8dp">
 
     <ExpandableListView android:id="@id/android:list"
               android:layout_width="match_parent" 
               android:layout_height="match_parent"
               android:background="#00FF00"
               android:layout_weight="1"
               android:drawSelectorOnTop="false"/>
 
     <TextView android:id="@id/android:empty"
               android:layout_width="match_parent" 
               android:layout_height="match_parent"
               android:background="#FF0000"
               android:text="No data"/>
 </LinearLayout>
 

Row Layout

The ExpandableListAdapter set in the ExpandableListActivity via setListAdapter(ExpandableListAdapter) provides the Views for each row. This adapter has separate methods for providing the group Views and child Views. There are a couple provided ExpandableListAdapters that simplify use of adapters: SimpleCursorTreeAdapter and SimpleExpandableListAdapter.

With these, you can specify the layout of individual rows for groups and children in the list. These constructor takes a few parameters that specify layout resources for groups and children. It also has additional parameters that let you specify which data field to associate with which object in the row layout resource. The SimpleCursorTreeAdapter fetches data from Cursors and the SimpleExpandableListAdapter fetches data from Lists of Maps.

Android provides some standard row layout resources. These are in the R.layout class, and have names such as simple_list_item_1, simple_list_item_2, and two_line_list_item. The following layout XML is the source for the resource two_line_list_item, which displays two data fields,one above the other, for each list row.

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:orientation="vertical">
 
     <TextView android:id="@+id/text1"
         android:textSize="16sp"
         android:textStyle="bold"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"/>
 
     <TextView android:id="@+id/text2"
         android:textSize="16sp"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"/>
 </LinearLayout>
 

You must identify the data bound to each TextView object in this layout. The syntax for this is discussed in the next section.

Binding to Data

You bind the ExpandableListActivity's ExpandableListView object to data using a class that implements the ExpandableListAdapter interface. Android provides two standard list adapters: SimpleExpandableListAdapter for static data (Maps), and SimpleCursorTreeAdapter for Cursor query results.

See also:

Summary

Inherited constants

From class android.app.Activity
From class android.content.Context
From interface android.content.ComponentCallbacks2

Inherited fields

From class android.app.Activity

Public constructors

ExpandableListActivity()

Public methods

ExpandableListAdapter getExpandableListAdapter()

Get the ExpandableListAdapter associated with this activity's ExpandableListView.

ExpandableListView getExpandableListView()

Get the activity's expandable list view widget.

long getSelectedId()

Gets the ID of the currently selected group or child.

long getSelectedPosition()

Gets the position (in packed position representation) of the currently selected group or child.

boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id)

Override this for receiving callbacks when a child has been clicked.

void onContentChanged()

Updates the screen state (current list and other views) when the content changes.

void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo)

Override this to populate the context menu when an item is long pressed.

void onGroupCollapse(int groupPosition)

Override this for receiving callbacks when a group has been collapsed.

void onGroupExpand(int groupPosition)

Override this for receiving callbacks when a group has been expanded.

void setListAdapter(ExpandableListAdapter adapter)

Provide the adapter for the expandable list.

boolean setSelectedChild(int groupPosition, int childPosition, boolean shouldExpandGroup)

Sets the selection to the specified child.

void setSelectedGroup(int groupPosition)

Sets the selection to the specified group.

Protected methods

void onRestoreInstanceState(Bundle state)

Ensures the expandable list view has been created before Activity restores all of the view states.

Inherited methods

From class android.app.Activity
From class android.view.ContextThemeWrapper
From class android.content.ContextWrapper
From class android.content.Context
From class java.lang.Object
From interface android.view.LayoutInflater.Factory2
From interface android.view.Window.Callback
From interface android.view.KeyEvent.Callback
From interface android.view.View.OnCreateContextMenuListener
From interface android.content.ComponentCallbacks2
From interface android.widget.ExpandableListView.OnChildClickListener
From interface android.widget.ExpandableListView.OnGroupCollapseListener
From interface android.widget.ExpandableListView.OnGroupExpandListener
From interface android.view.LayoutInflater.Factory
From interface android.content.ComponentCallbacks

Public constructors

ExpandableListActivity

Added in API level 1
ExpandableListActivity ()

Public methods

getExpandableListAdapter

Added in API level 1
ExpandableListAdapter getExpandableListAdapter ()

Get the ExpandableListAdapter associated with this activity's ExpandableListView.

Returns
ExpandableListAdapter

getExpandableListView

Added in API level 1
ExpandableListView getExpandableListView ()

Get the activity's expandable list view widget. This can be used to get the selection, set the selection, and many other useful functions.

Returns
ExpandableListView

See also:

getSelectedId

Added in API level 1
long getSelectedId ()

Gets the ID of the currently selected group or child.

Returns
long The ID of the currently selected group or child.

getSelectedPosition

Added in API level 1
long getSelectedPosition ()

Gets the position (in packed position representation) of the currently selected group or child. Use getPackedPositionType(long), getPackedPositionGroup(long), and getPackedPositionChild(long) to unpack the returned packed position.

Returns
long A packed position representation containing the currently selected group or child's position and type.

onChildClick

Added in API level 1
boolean onChildClick (ExpandableListView parent, 
                View v, 
                int groupPosition, 
                int childPosition, 
                long id)

Override this for receiving callbacks when a child has been clicked.

Callback method to be invoked when a child in this expandable list has been clicked.

Parameters
parent ExpandableListView: The ExpandableListView where the click happened
v View: The view within the expandable list/ListView that was clicked
groupPosition int: The group position that contains the child that was clicked
childPosition int: The child position within the group
id long: The row id of the child that was clicked
Returns
boolean True if the click was handled

onContentChanged

Added in API level 1
void onContentChanged ()

Updates the screen state (current list and other views) when the content changes.

See also:

onCreateContextMenu

Added in API level 1
void onCreateContextMenu (ContextMenu menu, 
                View v, 
                ContextMenu.ContextMenuInfo menuInfo)

Override this to populate the context menu when an item is long pressed. menuInfo will contain an ExpandableListView.ExpandableListContextMenuInfo whose packedPosition is a packed position that should be used with getPackedPositionType(long) and the other similar methods.

Called when a context menu for the view is about to be shown. Unlike onCreateOptionsMenu(Menu), this will be called every time the context menu is about to be shown and should be populated for the view (or item inside the view for AdapterView subclasses, this can be found in the menuInfo)).

Use onContextItemSelected(android.view.MenuItem) to know when an item has been selected.

It is not safe to hold onto the context menu after this method returns.

Parameters
menu ContextMenu: The context menu that is being built
v View: The view for which the context menu is being built
menuInfo ContextMenu.ContextMenuInfo: Extra information about the item for which the context menu should be shown. This information will vary depending on the class of v.

onGroupCollapse

Added in API level 1
void onGroupCollapse (int groupPosition)

Override this for receiving callbacks when a group has been collapsed.

Parameters
groupPosition int: The group position that was collapsed

onGroupExpand

Added in API level 1
void onGroupExpand (int groupPosition)

Override this for receiving callbacks when a group has been expanded.

Parameters
groupPosition int: The group position that was expanded

setListAdapter

Added in API level 1
void setListAdapter (ExpandableListAdapter adapter)

Provide the adapter for the expandable list.

Parameters
adapter ExpandableListAdapter

setSelectedChild

Added in API level 1
boolean setSelectedChild (int groupPosition, 
                int childPosition, 
                boolean shouldExpandGroup)

Sets the selection to the specified child. If the child is in a collapsed group, the group will only be expanded and child subsequently selected if shouldExpandGroup is set to true, otherwise the method will return false.

Parameters
groupPosition int: The position of the group that contains the child.
childPosition int: The position of the child within the group.
shouldExpandGroup boolean: Whether the child's group should be expanded if it is collapsed.
Returns
boolean Whether the selection was successfully set on the child.

setSelectedGroup

Added in API level 1
void setSelectedGroup (int groupPosition)

Sets the selection to the specified group.

Parameters
groupPosition int: The position of the group that should be selected.

Protected methods

onRestoreInstanceState

Added in API level 1
void onRestoreInstanceState (Bundle state)

Ensures the expandable list view has been created before Activity restores all of the view states.

Parameters
state Bundle: the data most recently supplied in onSaveInstanceState(Bundle).

See also:

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