After Honeycomb, Google said that bitmaps are managed by the heap (talked about here), so if a bitmap is no longer accessible, we can assume that GC takes care of it and frees it.
I wanted to create a demo that shows the efficiency of the ideas shown for the listView lecture (from here), so I made a small app. The app lets the user press a button, and then the listview scrolls all the way to the bottom, while it has 10000 items, which their content is the android.R.drawable items (name and image).
For some reason, I get out of memory even though I don't save any of the images, so my question is: How could it be? What is it that I'm missing?
I've tested the app on a Galaxy S III, and yet I keep getting out of memory exceptions if I use the native version of the adapter. I don't understand why it occurs, since I don't store anything.
Here's the code:
public class MainActivity extends Activity
{
private static final int LISTVIEW_ITEMS =10000;
long _startTime;
boolean _isMeasuring =false;
@Override
public void onCreate(final Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ListView listView=(ListView)findViewById(R.id.listView);
final Field[] fields=android.R.drawable.class.getFields();
final LayoutInflater inflater=(LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
// listen to scroll events , so that we publish the time only when scrolled to the bottom:
listView.setOnScrollListener(new OnScrollListener()
{
@Override
public void onScrollStateChanged(final AbsListView view,final int scrollState)
{
if(!_isMeasuring||view.getLastVisiblePosition()!=view.getCount()-1||scrollState!=OnScrollListener.SCROLL_STATE_IDLE)
return;
final long stopTime=System.currentTimeMillis();
final long scrollingTime=stopTime-_startTime;
Toast.makeText(MainActivity.this,"time taken to scroll to bottom:"+scrollingTime,Toast.LENGTH_SHORT).show();
_isMeasuring=false;
}
@Override
public void onScroll(final AbsListView view,final int firstVisibleItem,final int visibleItemCount,final int totalItemCount)
{}
});
// button click handling (start measuring) :
findViewById(R.id.button).setOnClickListener(new OnClickListener()
{
@Override
public void onClick(final View v)
{
if(_isMeasuring)
return;
final int itemsCount=listView.getAdapter().getCount();
listView.smoothScrollToPositionFromTop(itemsCount-1,0,1000);
_startTime=System.currentTimeMillis();
_isMeasuring=true;
}
});
// creating the adapter of the listView
listView.setAdapter(new BaseAdapter()
{
@Override
public View getView(final int position,final View convertView,final ViewGroup parent)
{
final Field field=fields[position%fields.length];
// final View inflatedView=convertView!=null ? convertView : inflater.inflate(R.layout.list_item,null);
final View inflatedView=inflater.inflate(R.layout.list_item,null);
final ImageView imageView=(ImageView)inflatedView.findViewById(R.id.imageView);
final TextView textView=(TextView)inflatedView.findViewById(R.id.textView);
textView.setText(field.getName());
try
{
final int imageResId=field.getInt(null);
imageView.setImageResource(imageResId);
}
catch(final Exception e)
{}
return inflatedView;
}
@Override
public long getItemId(final int position)
{
return 0;
}
@Override
public Object getItem(final int position)
{
return null;
}
@Override
public int getCount()
{
return LISTVIEW_ITEMS;
}
});
}
}
@all: I know that there are optimizations for this code (using the convertView and the viewHolder design pattern) as I've mentioned the video of the listView made by Google. Believe me, I know what's better; this is the whole point of the code.
The code above is supposed to show that it's better to use what you (and the video) shows. But first I need to show the naive way; even the naive way should still work, since I don't store the bitmaps or the views, and since Google has done the same test (hence they got a graph of performance comparison).
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