Android
android.app
public class

android.app.ExpandableListActivity

java.lang.Object
android.content.Context
android.content.ContextWrapper
android.view.ContextThemeWrapper
android.app.Activity ComponentCallbacks KeyEvent.Callback LayoutInflater.Factory View.OnCreateContextMenuListener Window.Callback
android.app.ExpandableListActivity View.OnCreateContextMenuListener ExpandableListView.OnChildClickListener ExpandableListView.OnGroupCollapseListener ExpandableListView.OnGroupExpandListener

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
         android:orientation="vertical"
         android:layout_width="fill_parent" 
         android:layout_height="fill_parent"
         android:paddingLeft="8"
         android:paddingRight="8">
 
     <ExpandableListView id="android:list"
               android:layout_width="fill_parent" 
               android:layout_height="fill_parent"
               android:background="#00FF00"
               android:layout_weight="1"
               android:drawSelectorOnTop="false"/>
 
     <TextView id="android:empty"
               android:layout_width="fill_parent" 
               android:layout_height="fill_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
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:orientation="vertical">
 
     <TextView id="text1"
         android:textSize="16"
         android:textStyle="bold"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"/>
 
     <TextView id="text2"
         android:textSize="16"
         android:layout_width="fill_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.

Summary

Constants inherited from class android.app.Activity
Constants inherited from class android.content.Context

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

Details

Public Constructors

public ExpandableListActivity()

Public Methods

public ExpandableListAdapter getExpandableListAdapter()

Get the ExpandableListAdapter associated with this activity's ExpandableListView.

public 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.

public long getSelectedId()

Gets the ID of the currently selected group or child.

Returns

  • The ID of the currently selected group or child.

public 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

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

public 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.

public void onContentChanged()

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

public 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 a AdapterView.AdapterContextMenuInfo whose position 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. Called when the context menu for this view is being built. It is not safe to hold onto the menu after this method returns.

public void onGroupCollapse(int groupPosition)

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

public void onGroupExpand(int groupPosition)

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

public void setListAdapter(ExpandableListAdapter adapter)

Provide the adapter for the expandable list.

public 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 The position of the group that contains the child.
childPosition The position of the child within the group.
shouldExpandGroup Whether the child's group should be expanded if it is collapsed.

Returns

  • Whether the selection was successfully set on the child.

public void setSelectedGroup(int groupPosition)

Sets the selection to the specified group.

Parameters

groupPosition The position of the group that should be selected.

Protected Methods

protected void onRestoreInstanceState(Bundle state)

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

Parameters

state the data most recently supplied in onSaveInstanceState(Bundle).
Copyright 2007 Google Inc. Build 0.9_r1-98467 - 14 Aug 2008 18:48