Android ArrayAdapter causes OutOfMemoryException (Content is only a TextView)

Question

I have an ArrayAdapter subclass called TestListAdpater whose constructor is the following:

public TestListAdapter(Context context,int viewResourceId, List<TestObjects>  
objects) {
    super(context, viewResourceId, objects);
    iHostViewID = viewResourceId;

     }

and whose getView method is the following:

@Override
public View getView(int pos, View convertView, ViewGroup parent){
View itemView = convertView;

LayoutInflater inflater =
   (LayoutInflater)hContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
itemView = inflater.inflate(iHostViewID, null);

TextView testTV = 
(TextView)itemView.findViewById(R.id.widget_listitem_test_TV);
testTV.setText("Testing...");

}

I then add 20 of these test items to the TestListAdapter, enough that I can scroll up and down through them. After a few cycles through all of them scrolling down to the bottom and then back up to the top, I receive an OutOfMemory exception and the app crashes. My questions are three:

Why is this occurring the first place? Doesn't ArrayAdapter keep views that have already been rendered in RAM so it doesn't have to reallocate anything when getView() is called for a view that has already been displayed at least once?
How can I absolutely prevent this from ever happening, no matter how frequently the user scrolls the listview?
Does LayoutInflater::inflate() always allocate new resources?

I have a feeling from looking at the source for Android's Adapter interface that the problem is caused by my always inflating a view in getView(); Adapter's comments claim that the argument convertView is "The old view to reuse, if possible". My real use case for the custom ArrayAdapter requires an override of getView(), so how can I implement the check for re-usability that Android's default ArrayAdapter apparently performs? (I didn't see any such check in ArrayAdapter's source after a cursory look)

Gavin2058 · Accepted Answer · 2014-05-07 02:09:16Z

1

try this:

private LayoutInflater mInflater;
Context mContext;
public TestListAdapter(Context context,int viewResourceId, List<TestObjects>  
objects) {
    super(context, viewResourceId, objects);

    this.mContext = context;
    this.mInflater = LayoutInflater.from(context);
    this.iHostViewID = viewResourceId;

     }
@Override
public View getView(int pos, View convertView, ViewGroup parent) {
    CollectHolder holder = null;
    if (convertView == null) {
        convertView = mInflater.inflate(iHostViewID, null);
        holder = new CollectHolder(convertView);
        convertView.setTag(holder);
    } else {
        holder = (CollectHolder) convertView.getTag();
    }
    holder.testTV.setText("Testing...");
    return convertView;
}

class CollectHolder {
    TextView testTV;

    public CollectHolder(View root) {
        this.testTV = (TextView) root
                .findViewById(R.id.widget_listitem_test_TV);
    }
}

answered May 7, 2014 at 2:09

Gavin2058

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CCJ Over a year ago

actually, just adding an if (convertView == null){itemView = <inflate view>}Else{itemView = convertView} seems to do the trick. Not sure what Android does to cache views (a pool, perhaps?) but it seems to work if you let it. Thanks for the hint!

Gavin2058 · Accepted Answer · 2014-05-07 03:29:45Z

1

My English is not good, I hope you understand. Do you know thread pool,yeah,for listView,it also has such a thing,we can call it"view pool".Of course inside storage is all item views,the view pool has a max size,you can call that maxNum. For example:when you enter into listView activity,Just show 5 items in visual range,so the maxNum.size()==6.What? Why is it 6 instead of 5?Don't worry,when you slide down below the ListView to display item, the topSide item should slide up ,This makes it possible for the first half of an item has been slipping out of the screen, while the lowermost one item and half did not enter the screen ,But it is already showing 6 items.Continue up the slide, the first item has completely disappeared from the screen, Where is it? Destroyed? No,Do you remember the view pool ? Right, in the view pool.Now the 6 item has completely display ,Continue up the slide, the upper will repeat the steps in front of it. For now, talk about bottom .First, go to view pool to find item size whether equals maxNum.If not,continue to create a new item view ,else then went to pick up the unUse item view from view pool.This view is Adapter.getView () method parameter convertView .For this cycle,You understand?

answered May 7, 2014 at 3:29

Gavin2058

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1 Comment

CCJ Over a year ago

yeah, I figured there would be a pool at work somewhere; my always calling inflate() effectively kept that pool from serving its purpose and led to the heap overflow. thanks again

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