Develop Reference

Android Listview GC_FOR_ALLOC freed: DDMS android.graphics.Bitmap

I'm having trouble with a listview in android. When I start scrolling down my List, it is very slow and I see that the GC is called. When I'm at the bottom of my List, everything works fine and smooth. I think that at this point my ViewHolder does the work.
But I can't find the source that is calling the GC. I searched which lead to:
DDMS 436816 byte[] 1 android.graphics.Bitmap nativeCreate
I can't interpret that line. My ArrayAdapter and it's getView method looks like this:
public class DiagnoseAdapter extends ArrayAdapter<Visualizer> {
#Override
public View getView(int position, View convertView, ViewGroup parent) {
int type = TYPE_DEFAULT;
final Visualizer item = getItem(position);
switch(item.getType()){
case TYPE_DEFAULT:
convertView = DefaultTextView.getView(position, convertView, mlayoutInflater, item, parent);
break;
// more cases/types
}
return convertView;
}
}
which is calling the following getView Method of the class DefaultTextView
public class DefaultTextView{
public static View getView(int position, View convertView, LayoutInflater layoutInflater, Visualizer item, ViewGroup parent){
ViewHolder holder;
if (convertView == null || item.getReleatedObject() == null || convertView.getTag()!=TAG_DEFAULT) {
convertView = layoutInflater.inflate(R.layout.diagnose_item, null);
holder = new ViewHolder();
holder.value = (TextView) convertView.findViewById(R.id.diagnose_function_value);
holder.name = (TextView) convertView.findViewById(R.id.diagnose_function_setname);
holder.mLinLayout = (LinearLayout) convertView.findViewById(R.id.default_linlayout);
convertView.setTag(TAG_DEFAULT);
convertView.setTag(R.layout.diagnose_item,holder);
item.setReleatedObject(convertView);
} else {
holder = (ViewHolder) convertView.getTag(R.layout.diagnose_item);
}
holder.value.setText(item.toString());
holder.name.setText(item.getToolTip());
holder.mLinLayout.removeAllViews();
if (item.getUpdateFlag(4)) {
if (holder.back == null){
holder.back = new ImageView(convertView.getContext());
holder.back.setScaleType(ScaleType.FIT_CENTER);
holder.back.setAdjustViewBounds(true);
holder.back.setImageBitmap(bm1);
}
holder.mLinLayout.addView(holder.back);
}
if (item.getUpdateFlag(1)) {
if (holder.update == null){
holder.update = new ImageView(convertView.getContext());
holder.update.setScaleType(ScaleType.FIT_CENTER);
holder.update.setAdjustViewBounds(true);
holder.update.setImageBitmap(bm2);
}
holder.mLinLayout.addView(holder.update);
}
if (item.getUpdateFlag(2)) {
if (holder.timer == null){
holder.timer = new ImageView(convertView.getContext());
holder.timer.setScaleType(ScaleType.FIT_CENTER);
holder.timer.setAdjustViewBounds(true);
holder.timer.setImageBitmap(bm3)
}
holder.mLinLayout.addView(holder.timer);
}
if (item.getUpdateFlag(3)) {
if (holder.log == null){
holder.log = new ImageView(convertView.getContext());
holder.log.setScaleType(ScaleType.FIT_CENTER);
holder.log.setAdjustViewBounds(true);
holder.log.setImageBitmap(bm4);
}
holder.mLinLayout.addView(holder.log);
}
if (item.getUpdateFlag(0)) {
if (holder.forward == null){
holder.forward = new ImageView(convertView.getContext());
holder.forward.setScaleType(ScaleType.FIT_CENTER);
holder.forward.setAdjustViewBounds(true);
holder.forward.setImageBitmap(bm5);
}
holder.mLinLayout.addView(holder.forward);
}
return convertView;
}
static class ViewHolder {
TextView name, value;
ImageView back, update, timer, log, forward;
LinearLayout mLinLayout;
}
}
Even if I comment the LinearLayout out, so I just have a List with two TextViews.
So my Question. Do I miss anything. Some stupid thing? How do I get my ListView smoother?
BTW: I read in a different thread, that it is happening if the ListView has the attribute android:cacheColorHint="#00000000. I don't have this attribute.
I hope anyone has a solution. Thanks!

About the source of GC calls. If I'm understanding your code correctly, everytime your ListView items are recycled and you call removeAllViews(), a previously dynamically created ImageView is removed and its Bitmap is garbage collected. So, Maybe those GC calls would be avoided if you use the same ImageView declaring it in your xml layout and just replace the Bitmap according to your getUpdateFlag().
And two more things about ListViews and Images. First thing is that if the image is too big, your ListView is going to be laggy no matter what. You would need to scale the image down if that is the case( Loading Large Bitmaps Efficiently). And second, maybe you would also need to implement a Lazy List, which loads images on demand, there is a famous question about that --> How do I do a lazy load of images in ListView?

I've finally solved my Problem. Like above, I thought the problem was based on the images of my list items. But that wasn't the problem. I just didn't use my ViewHolders and the getItemViewType(int position) method correctly. I have a list with many different item layouts and I saw, that my code above created a new convertView and a new ViewHolder for every single item, which wasn't supposed to be. I found a great tutorial about how to use multiple item layouts (see link below):
Multiple List Item Layouts

Recycling views in custom array adapter: how exactly is it handled?

I am having an unclear issue concerning the recycling of views in a getView method of a custom array adapter.
I understand that elements are reused, but how do I know exact what to implement in the first part of the if statement, and what in the second?
Right now I am having following code. I came to this question due to dropping the code in the second part of the statement which results in a list of the first 9 elements, which are repeated numberous times instead of all elements. I didn't really know what is causing this exactly...
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
if (row == null) {
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
row = inflater.inflate(layoutResourceId, parent, false);
title = getItem(position).getTitle();
size = calculateFileSize(position);
txtTitle = (TextView) row.findViewById(R.id.txtTitle);
tvFileSize = (TextView) row.findViewById(R.id.tvFileSize);
txtTitle.setText(title);
tvFileSize.setText(size);
} else {
title = getItem(position).getTitle();
size = calculateFileSize(position);
txtTitle = (TextView) row.findViewById(R.id.txtTitle);
tvFileSize = (TextView) row.findViewById(R.id.tvFileSize);
txtTitle.setText(title);
tvFileSize.setText(size);
}
return row;
}

It's easy. The first time no row is created, so you have to inflate them. Afterwards, the Android os may decide to recycle the views that you already inflated and that are not visible anymore. Those are already inflated and passed into the convertView parameter, so all you have to do is to arrange it to show the new current item, for example placing the right values into the various text fields.
In short, in the first part you should perform the inflation AND fill the values, in the second if (if convertView != null) you should only overwrite the field because, given the view has been recycled, the textviews contain the values of the old item.
This post and this are good starting points

I understand that elements are reused, but how do I know exact what to implement in the first part of the if statement, and what in the second?
The organization is quite simple once you get the hang of it:
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
/* This is where you initialize new rows, by:
* - Inflating the layout,
* - Instantiating the ViewHolder,
* - And defining any characteristics that are consistent for every row */
} else {
/* Fetch data already in the row layout,
* primarily you only use this to get a copy of the ViewHolder */
}
/* Set the data that changes in each row, like `title` and `size`
* This is where you give rows there unique values. */
return convertView;
}
For detailed explanations of how ListView's RecycleBin works and why ViewHolders are important watch Turbo Charge your UI, a Google I/O presentation by Android's lead ListView programmers.

You want to create a ViewHolder class in your MainActivity. Something like
static class ViewHolder
{
TextView tv1;
TextView tv2;
}
then in your getView, the first time you get your Views from your xml in the if and reuse them after that in the else
View rowView = convertView;
if (rowView == null)
{
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
rowView = inflater.inflate(R.layout.layout_name_to_inflate, parent, false);
holder = new ViewHolder();
holder.tv1= (TextView) rowView.findViewById(R.id.textView1);
holder.tv2 = (RadioGroup) rowView.findViewById(R.id.textView2);
rowView.setTag(holder);
}
else
{
holder = (ViewHolder) rowView.getTag();
}

I would recommend that you use the View holder and convertview pattern to create your listView as it will be more efficient.Here is a good explanation of how it works with a re-use strategy. This will answer your question on how re-cycling works. If you want to refer to a code sample, I have it on GitHub.
Hope this helps.

The last part of the question I really couldn't grasp without a picture of the effect but for the first part "what to implement in the first part of the if statement, and what in the second" I think I've found the this implementation very common.
You would find the view references first and store them to a static class ViewHolder which then you attach to the tag of the new inflated view. As the listview recycles the views and a convertView is passed getView you get the ViewHolder from the convertView's tag so you don't have to find the references again (which greatly improves performance) and update the view data with that of your object at the position given.
Technically you don't care what position the view was since all you care for is the references to the views you need to update which are held within it's ViewHolder.
#Override
public View getView(int position, View convertView, ViewGroup container) {
ViewHolder holder;
Store store = getItem(position);
if (convertView == null) {
convertView = mLayoutInflater.inflate(R.layout.item_store, null);
// create a holder to store references
holder = new ViewHolder();
// find references and store in holder
ViewGroup logoPhoneLayout = (ViewGroup) convertView
.findViewById(R.id.logophonelayout);
ViewGroup addressLayout = (ViewGroup) convertView
.findViewById(R.id.addresslayout);
holder.image = (ImageView) logoPhoneLayout
.findViewById(R.id.image1);
holder.phone = (TextView) logoPhoneLayout
.findViewById(R.id.textview1);
holder.address = (TextView) addressLayout
.findViewById(R.id.textview1);
// store holder in views tag
convertView.setTag(holder);
} else {
// Retrieve holder from view
holder = (ViewHolder) convertView.getTag();
}
// fill in view with our store (at this position)
holder.phone.setText(store.phone);
holder.address.setText(store.getFullAddress());
UrlImageViewHelper.setUrlDrawable(holder.image, store.storeLogoURL,
R.drawable.no_image);
return convertView;
}
private static class ViewHolder {
ImageView image;
TextView phone;
TextView address;
}

Clearing View cache of ListView

I have a ListView that I put through a complex bit of coding. The list changes often with different types of data that require different views. On rare occasion, I'll end up with 1 view being reused by Android for a row that's supposed to look different. It seems to only happen when the data being displayed radically changes. I was hoping there was a way to programmatically wipe the ListView's memory clean. Is this possible?
Here is the beginning of my getView:
#Override
public View getView(int position, View convertView, ViewGroup parent) {
SearchHolder holder = null;
int type = getItemViewType(position);
if (null == convertView) {
holder = new SearchHolder();
if (type == SEARCH_TYPE_FREETEXT) {
convertView = mInflater.inflate(R.layout.layout_search_item_freetext, null);
holder.txtText = (TextView) convertView.findViewById(R.id.search_itemname);
holder.vHeaderWrapper = (LinearLayout) convertView.findViewById(R.id.search_headerwrapper);
holder.txtHeader = (TextView) convertView.findViewById(R.id.search_header);
}
else {
if (items.get(position).mData == null) {
convertView = mInflater.inflate(R.layout.layout_loadmoreresults_white, null);
}
else {
convertView = mInflater.inflate(R.layout.layout_search_item, null);
holder.txtText = (TextView) convertView.findViewById(R.id.search_itemname);
holder.vHeaderWrapper = (LinearLayout) convertView.findViewById(R.id.search_headerwrapper);
holder.txtHeader = (TextView) convertView.findViewById(R.id.search_header);
}
}
convertView.setTag(holder);
}
else {
holder = (SearchHolder)convertView.getTag();
}
...

ListView does something called "recycling" when you scroll through a list, and what you will need to do is override the getView() method to update the individual listView item that is being recycled. By default android does not clear out these views. Check out the following link on ListView recycling:
http://mobile.cs.fsu.edu/the-nuance-of-android-listview-recycling-for-n00bs/
Without code it is hard to tell if you already know about this or not, but this is the cause of such problems in my experience.

If you use more than one layout for your list items then I suggest to inflate the appropriate layout from the xml every time in the getView() method.

First Adapter image is incorrect

For some reason, my first image displays correctly, then gets overwrriten with another user's image. Any ideas:
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
ViewHolder holder;
if( convertView == null ){
vi = inflater.inflate(R.layout.feed_item, null);
holder=new ViewHolder();
holder.userImage = (ImageView) vi.findViewById(R.id.feed_userimage);
vi.setTag(holder);
} else {
holder=(ViewHolder)vi.getTag();
}
if(user.has("image") &&
user.getString("image") != null &&
!user.getString("image").equals("null")) {
holder.userImage.setTag(user.getString("image"));
imageLoader.DisplayImage(user.getString("image"), act, holder.userImage,USER_IMAGE_SIZE);
} else {
holder.userImage.setImageDrawable(null);
}

Try this fix
if(user.has("image") &&
user.getString("image") != null &&
!user.getString("image").equals("null")) {
holder.userImage.setTag(user.getString("image"));
imageLoader.DisplayImage(user.getString("image"), act, holder.userImage,USER_IMAGE_SIZE);
} else {
holder.userImage.setTag(null);//add this line
holder.userImage.setImageDrawable(null);
}

It is happenning because you are using convertView. The convertView passed to the getView method is essentially a view object you had created (by inflating) in a previous getView call (which is no more be needed because it is not visible anymore, due to scrolling).
You are assuming that every time getView is called a new view is created, whereas you are actually using previously created views. The convertView is passed as an optimisation so that too many views does not have to be created when only a few are visible.
So the setTag call actually overwrites a previously created view's tag.
You should reconsider rewriting your code without using tags. Or, you could always inflate the view, instead of only inflating when the convertView is not null. But I wouldn't reccommend this approach as for a long list it would mean too many unnecessary views in the memory.

How to implement a view holder?

i am using a viewholder to display from a dynamic arrayadapter.it works but the data displayed changes irregularly when i scroll the List.i want my List View to be populated only once ,Not all the time when i scroll my list. Any suggestion?
Here is my Code
public View getView(int position, View convertView, ViewGroup parent) {
// A ViewHolder keeps references to children views to avoid unneccessary calls
// to findViewById() on each row.
ViewHolder holder;
// When convertView is not null, we can reuse it directly, there is no need
// to reinflate it. We only inflate a new View when the convertView supplied
// by ListView is null.
if (convertView == null) {
convertView = mInflater.inflate(R.layout.sample, null);
// Creates a ViewHolder and store references to the two children views
// we want to bind data to.
holder = new ViewHolder();
holder.name = (TextView) convertView.findViewById(R.id.text);
holder.icon = (ImageView) convertView.findViewById(R.id.icon);
convertView.setTag(holder);
} else {
// Get the ViewHolder back to get fast access to the TextView
// and the ImageView.
holder = (ViewHolder) convertView.getTag();
}
// Bind the data efficiently with the holder.
if(_first==true)
{
if(id<myElements.size())
{
holder.name.setText(myElements.get(id));
holder.icon.setImageBitmap( mIcon1 );
id++;
}
else
{
_first=false;
}
}
//holder.icon.setImageBitmap(mIcon2);
/*try{
if(id<myElements.size())
id++;
else
{
id--;
}
}
catch(Exception e)
{
android.util.Log.i("callRestService",e.getMessage());
}*/
return convertView;
}
static class ViewHolder {
TextView name;
ImageView icon;
}
when the list is loaded it looks like this : http://i.stack.imgur.com/NrGhR.png after scrolling some data http://i.stack.imgur.com/sMbAD.png it looks like this, and again if i scroll to the beginning it looks http://i.stack.imgur.com/0KjMa.png
P.S : my list have to be in alphabetic order

Have you tried this?
public View getView(int position, View convertView, ViewGroup parent) {
// A ViewHolder keeps references to children views to avoid unneccessary calls
// to findViewById() on each row.
ViewHolder holder;
// When convertView is not null, we can reuse it directly, there is no need
// to reinflate it. We only inflate a new View when the convertView supplied
// by ListView is null.
if (convertView == null) {
convertView = mInflater.inflate(R.layout.sample, null);
// Creates a ViewHolder and store references to the two children views
// we want to bind data to.
holder = new ViewHolder();
holder.name = (TextView) convertView.findViewById(R.id.text);
holder.icon = (ImageView) convertView.findViewById(R.id.icon);
convertView.setTag(holder);
} else {
// Get the ViewHolder back to get fast access to the TextView
// and the ImageView.
holder = (ViewHolder) convertView.getTag();
}
// Bind the data efficiently with the holder.
holder.name.setText(myElements.get(id));
holder.icon.setImageBitmap( mIcon1 );
return convertView;
}
static class ViewHolder {
TextView name;
ImageView icon;
}
If yes, what's wrong with it?
I don't think loading all the rows at once is a good idea. You will end up having plenty of useless Views in memory that are going to slow the application down for nothing.
Views and operations on views (like inflate, findViewById, getChild..) are expensive, you should try to reuse them as much as possible. That's why we use ViewHolders.

You would need to write you own version of ListView to do that (which is bad). If the ListView doesn't work properly, it probably means that you are doing something wrong.
Where does the id element come from? You are getting the position in your getView() method, so you don't need to worry about exceeding list bounds. The position is linked to the element position in your list, so you can get the correct element like this:
myElements.get(position);
When the data in your list changes, you can call this:
yourAdapter.notifyDataSetChanged()
That will rebuild your list with new data (while keeping your scrolling and stuff).