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POListView performance is slow
 

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  1. POListView performance is slow
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    <p>I have a custom <code>ListView</code> where I display some weapons which are retrieved from a local database. I have a total of 88 rows, for each row a text and an image is set each time <code>getView()</code> is called. The <code>ListView</code> lags while scrolling fast and the garbage collector is going insane, deleting some 1M objects per second. I'm not getting why. </p> <p>Before I post my <code>Adapter</code> implementation, some explanation about how the Image is set. My <strong>Weapon</strong> class is simply a data holder with setters and getters. This is how names and images are getting set when the database gets created (yeah it might seem very strange, but all other solutions work even more slowly):</p> <pre><code> private Weapon buildWeapon(Cursor cursor) { Weapon w = new Weapon(); w.setId(cursor.getLong(0)); w.setName(cursor.getString(1)); w.setImage(Constants.ALL_WEAPON_IMAGES[(int) cursor.getLong(0)-1]); return w; } </code></pre> <p>So I have an <code>Array</code> containing all weapon images in the form of <code>R.drawable.somegun</code>. The data structure is implemented such way that ID-1 always points to the right drawable reference in my <code>Array</code>. The image field in the Weapon class is an <code>Integer</code>. Now you have an idea how my <code>getImage()</code> method works and below goes my <code>Adapter</code>:</p> <pre><code> public class Weapon_Adapter extends BaseAdapter { private List&lt;Weapon&gt; items; private LayoutInflater inflater = null; private WeaponHolder weaponHolder; private Weapon wp; static class WeaponHolder { public TextView text; public ImageView image; } // Context and all weapons of specified class are passed here public Weapon_Adapter(List&lt;Weapon&gt; items, Context c) { this.items = (List&lt;Weapon&gt;) items; inflater = LayoutInflater.from(c); Log.d("Adapter:", "Adapter created"); } @Override public int getCount() { return items.size(); } @Override public Weapon getItem(int position) { return items.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { wp = (Weapon) getItem(position); if (convertView == null) { convertView = inflater.inflate(R.layout.category_row, null); weaponHolder = new WeaponHolder(); weaponHolder.text = (TextView) convertView .findViewById(R.id.tvCatText); weaponHolder.image = (ImageView) convertView .findViewById(R.id.imgCatImage); convertView.setTag(weaponHolder); } weaponHolder = (WeaponHolder) convertView.getTag(); weaponHolder.text.setText(wp.getName()); weaponHolder.image.setImageResource(wp.getImage()); // weaponHolder.image.setImageResource(R.drawable.ak74m); return convertView; }} </code></pre> <p>Now the strange thing: using the outcommented line to statically set the same image for all items <strong>removes all lags and GC in not even called once!</strong> I'm not getting it.. <code>wp.getImage()</code> returns exactly the same thing, only <code>R.drawable.name</code> is different for each weapon. But GC removes tons of objects and the <code>ListView</code> lags while scrolling. Any ideas what I'm doing wrong?</p> <p><strong>UPDATE</strong></p> <p>I've moved setting images to an <code>AsyncTask</code> and the lag is gone now:</p> <pre><code> public class AsyncImageSetter extends AsyncTask&lt;Void, Void, Void&gt; { private ImageView img; private int image_resId; private Bitmap bmp; private Context c; public AsyncImageSetter(Context c, ImageView img, int image_ResId, Bitmap bmp) { this.img = img; this.image_resId = image_ResId; this.bmp = bmp; this.c = c; } @Override protected Void doInBackground(Void... params) { bmp = BitmapFactory.decodeResource(c.getResources(), image_resId); return null; } @Override protected void onPostExecute(Void result) { img.setImageBitmap(bmp); bmp = null; super.onPostExecute(result); } } </code></pre> <p>However, GC is still called like crazy and RAM consumption increases when scrolling the whole List up and down. The question is now: <strong>how can I optimize image recycling to avoid RAM usage increase?</strong> </p>
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    1. COuse lazy loading technique to load images. check this link http://stackoverflow.com/questions/16789676/caching-images-and-displaying/16978285#16978285 might help you also if the image is large try to scale down the image
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    2. COI've read about that and it's suitable for loading bunch of data from somewhere outside the app. I have very limited number of images and they all come from the drawable folder. I'm trying to figure out why the outcommented line works fast while my getImage() method which does pretty much the same causes the List to lag.. The images are not really large and get scaled by the ImageView's ScaleType parameter
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    3. COHow big is each image?
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