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Android Reference

ExpandableListActivity


android.app

Class ExpandableListActivity

  • All Implemented Interfaces:
    ComponentCallbacks, ComponentCallbacks2, KeyEvent.Callback, LayoutInflater.Factory, LayoutInflater.Factory2, View.OnCreateContextMenuListener, Window.Callback, ExpandableListView.OnChildClickListener, ExpandableListView.OnGroupCollapseListener, ExpandableListView.OnGroupExpandListener

    public class ExpandableListActivity
extends Activity
implements 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 android.R.id#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 android.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:
    setListAdapter(android.widget.ExpandableListAdapter), ExpandableListView

    • Constructor Detail

      • ExpandableListActivity

        public ExpandableListActivity()

    • Method Detail

      • onChildClick

        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.

        Specified by:
        onChildClick in interface ExpandableListView.OnChildClickListener
        Parameters:
        parent - The ExpandableListView where the click happened
        v - The view within the expandable list/ListView that was clicked
        groupPosition - The group position that contains the child that was clicked
        childPosition - The child position within the group
        id - The row id of the child that was clicked
        Returns:
        True if the click was handled

      • onGroupCollapse

        public void onGroupCollapse(int groupPosition)
        Override this for receiving callbacks when a group has been collapsed.
        Specified by:
        onGroupCollapse in interface ExpandableListView.OnGroupCollapseListener
        Parameters:
        groupPosition - The group position that was collapsed

      • onGroupExpand

        public void onGroupExpand(int groupPosition)
        Override this for receiving callbacks when a group has been expanded.
        Specified by:
        onGroupExpand in interface ExpandableListView.OnGroupExpandListener
        Parameters:
        groupPosition - The group position that was expanded

      • setListAdapter

        public void setListAdapter(ExpandableListAdapter adapter)
        Provide the adapter for the expandable list.

      • getExpandableListView

        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.
        See Also:
        ExpandableListView

      • getExpandableListAdapter

        public ExpandableListAdapter getExpandableListAdapter()
        Get the ExpandableListAdapter associated with this activity's ExpandableListView.

      • getSelectedId

        public long getSelectedId()
        Gets the ID of the currently selected group or child.
        Returns:
        The ID of the currently selected group or child.

      • setSelectedChild

        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.

      • setSelectedGroup

        public void setSelectedGroup(int groupPosition)
        Sets the selection to the specified group.
        Parameters:
        groupPosition - The position of the group that should be selected.


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