Android - Custom ListView Adapter - Multi Selection remove - Indexoutofbounds - why?

Question

I have a custom Listview using a adapter class to extend ArrayAdapter of a Item class. I have the ability to change between choice modes of NONE,Single and Multi. This all works fine. What I am trying to implement now is a method to removes items from the list view (and adapter) with multiple selection when in the multi choice mode. However I get IndexOutOFBounds Exceptions when doing either of the following; 1) remove last item in listview in SINGLE choice mode (Note: anything before last item remove ok) 2) In multi selection choice mode I once again can not remove last item 3) again in multi selection mode I can remove single selected items before last item but 2 or more selections result in index out of bounds errors again.

I added debug log to show position being removed and size of getCheckItemPositions() and my for loop counter (e.g. i) and finally the item title of the item being removed. If I comment out the actual listadpter.remove(position) line then the log output seems to indicator all is working fine So I am now suspecting the issue falls into my adapter class getView method. But my brain is exhausted and I am stuck.

MainActivity.class - removeItems method called from a button view object;

private void removeItems() {
    final SparseBooleanArray checkedItems = listView.getCheckedItemPositions();
    //final long[] checkedItemIds = listView.getCheckedItemIds();
    final int checkedItemsCount = checkedItems.size();

    Log.d("drp", "Adapter Count is: " + Integer.toString(mMyListViewAdapter.getCount()));
    if (checkedItems != null) {
        for (int i = checkedItemsCount-1; i >= 0 ; --i) {
            // This tells us the item position we are looking at
            // --
            final int position = checkedItems.keyAt(i);
            // This tells us the item status at the above position
            // --
            final boolean isChecked = checkedItems.valueAt(i);

            if (isChecked) {
                Item item = mMyListViewAdapter.getItem(position);
                Log.d("drp", "removing : " + Integer.toString(position) + " of " +Integer.toString(checkedItemsCount) + "-" + Integer.toString(i) + " - Title: " + mMyListViewAdapter.getItem(position).getTitle());
                mMyListViewAdapter.remove(item);

            }
        }
    }
}

Adapter Class;

public class MyListViewAdapter extends ArrayAdapter<Item>  implements OnItemClickListener{

private LayoutInflater mInflator;

/**
 * This is my view holder for getView method so don't need to call
 * findViewById all the time which results in speed increase
 */
static class ViewHolder {

    public TextView txtTitle;
    public TextView txtDescription;
    public TextView txtSessionCount;
    public ImageView listThumbnailImage;
    public ImageView listStatusIndicatorImage;
    public InertCheckBox Checkbox;
}

/**
 * Constructor from a list of items
 */
public MyListViewAdapter(Context context, List<Item> items) {
    super(context, 0, items);
    mInflator = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // This is how you would determine if this particular item is checked
    // when the view gets created
    // --
    final ListView lv = (ListView) parent;
    final boolean isChecked = lv.isItemChecked(position);
    final int selectionMode = lv.getChoiceMode();

    // The item we want to get the view for
    // --
    Item item = getItem(position);

    // Re-use the view if possible (recycle)
    // --
    ViewHolder holder = null;
    if (convertView == null) {
        convertView = mInflator.inflate(R.layout.listview_row, null);
        holder = new ViewHolder();
        holder.txtTitle = (TextView) convertView.findViewById(R.id.title);
        holder.txtDescription = (TextView) convertView.findViewById(R.id.description);
        holder.txtSessionCount = (TextView) convertView.findViewById(R.id.session_count);
        holder.listThumbnailImage = (ImageView) convertView.findViewById(R.id.list_image);
        holder.listStatusIndicatorImage = (ImageView) convertView.findViewById(R.id.status);
        holder.Checkbox = (InertCheckBox) convertView.findViewById(R.id.inertCheckBox);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder)convertView.getTag();
    }
    holder.txtTitle.setText(item.getTitle());
    holder.txtDescription.setText(item.getDescription());
    holder.txtSessionCount.setText(item.getSessionCount());
    holder.listThumbnailImage.setImageBitmap((Bitmap) item.getThumbnailImage());        
    switch (selectionMode) {
    case ListView.CHOICE_MODE_NONE:
        holder.Checkbox.setVisibility(InertCheckBox.GONE);
        holder.listStatusIndicatorImage.setVisibility(ImageView.VISIBLE);
        holder.listStatusIndicatorImage.setImageBitmap((Bitmap) item.getListIndicatorImage());
        break;
    //case ListView.CHOICE_MODE_SINGLE: case ListView.CHOICE_MODE_MULTIPLE:
    default:
        holder.listStatusIndicatorImage.setVisibility(ImageView.GONE);
        holder.Checkbox.setVisibility(InertCheckBox.VISIBLE);
        holder.Checkbox.setButtonDrawable(R.drawable.checkbox);
        holder.Checkbox.setChecked(isChecked);
        break;
    }           


    return convertView;
}

@Override
public long getItemId(int position) {
    return getItem(position).getId();
}

@Override
public boolean hasStableIds() {
    return true;
}

And Item Class - first half;

public class Item implements Comparable<Item> {

private long id;
private String title;
private String description;
private String session_count;
private Bitmap listImage;
private Bitmap statusImage;

public Item(long id, String title, String description, String session_count, Bitmap listImage, Bitmap statusImage) {
    super();
    this.id = id;
    this.title = title;
    this.description = description;
    this.session_count = session_count;
    this.listImage = listImage;
    this.statusImage = statusImage;
}

public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

public String getTitle() {
    return title;
}

Here is visual of my debug log tracking item removals

07-23 22:59:14.910: D/drp(19104): Adapter Count is: 51
07-23 22:59:14.910: D/drp(19104): removing : 50 of 4-3 - Title: Test 50 - testing
07-23 22:59:14.910: D/drp(19104): removing : 49 of 4-2 - Title: Test 49 - testing
07-23 22:59:14.910: D/drp(19104): removing : 48 of 4-1 - Title: Test 48 - testing

Again if I comment out the "mMyListViewAdapter.remove(item);" line in MainActivity not crashes and log seems to indicated its working as expected. Can anyone see my error that results in my Index Out Of Bounds Exception?

Also I am using SDK 4.0.4 API 15.

Many Thanks,

Paul.

Addition - full log output

        07-25 00:21:53.235: D/AbsListView(25952): Get MotionRecognitionManager
        07-25 00:21:53.270: D/dalvikvm(25952): GC_CONCURRENT freed 89K, 3% free 13027K/13383K, paused 1ms+2ms
        07-25 00:21:53.430: D/dalvikvm(25952): GC_CONCURRENT freed 207K, 4% free 13232K/13703K, paused 3ms+2ms
        07-25 00:21:53.630: D/CLIPBOARD(25952): Hide Clipboard dialog at Starting input: finished by someone else... !
        07-25 00:21:54.930: D/dalvikvm(25952): GC_FOR_ALLOC freed 189K, 4% free 13331K/13767K, paused 10ms
        07-25 00:21:54.930: I/dalvikvm-heap(25952): Grow heap (frag case) to 13.610MB for 408976-byte allocation
        07-25 00:21:54.940: D/dalvikvm(25952): GC_FOR_ALLOC freed 6K, 4% free 13724K/14215K, paused 9ms
        07-25 00:21:54.950: D/dalvikvm(25952): GC_FOR_ALLOC freed 0K, 4% free 13724K/14215K, paused 9ms
        07-25 00:21:54.950: I/dalvikvm-heap(25952): Grow heap (frag case) to 13.994MB for 408976-byte allocation
        07-25 00:21:54.960: D/dalvikvm(25952): GC_FOR_ALLOC freed 0K, 4% free 14124K/14663K, paused 9ms
        07-25 00:21:54.970: D/dalvikvm(25952): GC_FOR_ALLOC freed 0K, 4% free 14124K/14663K, paused 9ms
        07-25 00:21:54.975: I/dalvikvm-heap(25952): Grow heap (frag case) to 14.384MB for 408976-byte allocation
        07-25 00:21:54.995: D/dalvikvm(25952): GC_CONCURRENT freed 0K, 4% free 14523K/15111K, paused 1ms+1ms
        07-25 00:21:55.005: D/dalvikvm(25952): GC_FOR_ALLOC freed 0K, 4% free 14523K/15111K, paused 9ms
        07-25 00:21:55.005: I/dalvikvm-heap(25952): Grow heap (frag case) to 14.774MB for 408976-byte allocation
        07-25 00:21:55.020: D/dalvikvm(25952): GC_FOR_ALLOC freed 0K, 5% free 14923K/15559K, paused 9ms
        07-25 00:21:55.030: D/dalvikvm(25952): GC_FOR_ALLOC freed <1K, 5% free 14923K/15559K, paused 9ms
        07-25 00:21:55.030: I/dalvikvm-heap(25952): Grow heap (frag case) to 15.165MB for 408976-byte allocation
        07-25 00:21:55.040: D/dalvikvm(25952): GC_FOR_ALLOC freed 0K, 5% free 15322K/16007K, paused 10ms
        07-25 00:21:55.055: D/dalvikvm(25952): GC_FOR_ALLOC freed 0K, 5% free 15722K/16455K, paused 9ms
        07-25 00:21:55.110: D/dalvikvm(25952): GC_FOR_ALLOC freed 157K, 5% free 16145K/16903K, paused 9ms
        07-25 00:21:56.565: E/SKIA(25952): FimgApiStretch:stretch failed
        07-25 00:21:56.690: E/SKIA(25952): FimgApiStretch:stretch failed
        07-25 00:21:56.710: E/SKIA(25952): FimgApiStretch:stretch failed
        07-25 00:22:00.545: D/drp(25952): Adapter Count is: 51
        07-25 00:22:00.545: D/drp(25952): removing : 49 of 2-2 - Title: Test 49 - testing
        07-25 00:22:00.545: D/drp(25952): removing : 48 of 2-1 - Title: Test 48 - testing
        07-25 00:22:00.545: D/drp(25952): removing : 47 of 2-0 - Title: Test 47 - testing
        07-25 00:22:00.550: D/AndroidRuntime(25952): Shutting down VM
        07-25 00:22:00.550: W/dalvikvm(25952): threadid=1: thread exiting with uncaught exception (group=0x40c6f1f8)
        07-25 00:22:00.560: E/AndroidRuntime(25952): FATAL EXCEPTION: main
        07-25 00:22:00.560: E/AndroidRuntime(25952): java.lang.IndexOutOfBoundsException: Invalid index 48, size is 48
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at java.util.ArrayList.get(ArrayList.java:304)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.ArrayAdapter.getItem(ArrayAdapter.java:337)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at au.drp.mylistview.MyListViewAdapter.getItemId(MyListViewAdapter.java:107)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.AbsListView.confirmCheckedPositionsById(AbsListView.java:5956)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.AbsListView.handleDataChanged(AbsListView.java:5999)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.ListView.layoutChildren(ListView.java:1535)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.AbsListView.onLayout(AbsListView.java:2254)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.View.layout(View.java:11467)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.ViewGroup.layout(ViewGroup.java:4237)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:925)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.View.layout(View.java:11467)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.ViewGroup.layout(ViewGroup.java:4237)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.View.layout(View.java:11467)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.ViewGroup.layout(ViewGroup.java:4237)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1644)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1502)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1415)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.View.layout(View.java:11467)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.ViewGroup.layout(ViewGroup.java:4237)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.View.layout(View.java:11467)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.ViewGroup.layout(ViewGroup.java:4237)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1721)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2678)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.os.Handler.dispatchMessage(Handler.java:99)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.os.Looper.loop(Looper.java:137)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at android.app.ActivityThread.main(ActivityThread.java:4514)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at java.lang.reflect.Method.invokeNative(Native Method)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at java.lang.reflect.Method.invoke(Method.java:511)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
        07-25 00:22:00.560: E/AndroidRuntime(25952):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)

Answer 1

There appears to be a bug in AbsListView that causes this issue. It can happen with any subclass of AbsListView, including ListView and GridView.

In single- and multi-choice mode, the ListView responds to a notifyDataSetChanged() call on its adapter by verifying the set of checked items in confirmCheckedPositionsById(). Since the selected item(s) have already been deleted from the dataset at that point, the adapter will throw an exception. Notably, this issue only occurs if the adapter's hasStableIds() method returns true.

Loosely speaking, this is the relevant path:

1. You select one or more items in the ListView
2. The ListView updates its list of selected items
3. You click the delete button
4. The item(s) are removed from your dataset
5. You call notifyDataSetChanged() on your adapter, and it notifies its observers that the dataset has changed. The ListView is one of those observers.
6. Next time the ListView is redrawn, it sees the adapter's notification and calls handleDataChanged(). At this point, the ListView still thinks that our now-deleted items are selected and in the dataset.
7. The handleDataChanged() method calls confirmCheckedPositionsById(), which in turn tries to call getItemId() on the adapter using a stale position. If the deleted item happens to be near the end of the list, this position is likely to be out of bounds for the array, and the adapter will throw IndexOutOfBoundsException.

Two possible workarounds are as follows:

• Create a new adapter every time the dataset changes, as noted in other answers. This has the unfortunate effect of losing the current scroll position unless it's saved and restored manually.

• Clear the selected items by calling clearChoices() on the ListView (or GridView) before you call notifyDataSetChanged() on the adapter. The selected items will be deleted anyhow, so losing the current selection state is unlikely to be a problem. This method will preserve the scroll position and should prevent flickering while the list is being updated.

Answer 2

The bug in confirmCheckedPositionsById (bullet #7 in acj's answer) causes getItemId to get called on a stale position. However, it will get called again with the correct position to refresh the layout. When I ran into this problem I updated the custom Adapter's getItemId like so

@Override
public long getItemId(int position) {
    return position < getCount() ? getItem(position).getId() : -1;
}

Answer 3

Ok I solved the issue!!! YAY!

What I had to do to prevent the IndexOutOFBounds Exception was to reset the list view adapter so to refresh the list view contents. So the magic line was

 listView.setAdapter(mMyListViewAdapter);

However I believe this is not the best practise to use when working with a list view and its better to update the content of the adapter that the list view is attached to. But I not quite sure how to go about that?

Anyway he is my updated remove method code.

private void removeItems() {
    final SparseBooleanArray checkedItems = listView.getCheckedItemPositions();

    if (checkedItems != null) {
        final int checkedItemsCount = checkedItems.size();

        // Lets get the position of the view to scroll to before the first checked 
        // item to restore scroll position
        //          
        int topPosition = checkedItems.keyAt(0) - 1;            

        listView.setAdapter(null);
        for (int i = checkedItemsCount - 1; i >= 0 ; i--) {
            // This tells us the item position we are looking at
            // --
            final int position = checkedItems.keyAt(i);

            // This tells us the item status at the above position
            // --
            final boolean isChecked = checkedItems.valueAt(i);
            if (isChecked) {
                Item item = mMyListViewAdapter.getItem(position);
                mMyListViewAdapter.remove(item);
                //mMyListViewAdapter.notifyDataSetChanged();

            }               
        }
        listView.setAdapter(mMyListViewAdapter);
        //if topPosition is -1 then item zero is positioned by default.
        listView.setSelection(topPosition);
    }
}