Develop Reference

Listview lags; issue with cache file?

I have experienced quite a bit of lag recently when using ListView in one of my applications. About the same time the problem manifested itself, I started getting the following error message upon shutting down the application.
E/libEGL(8501): error creating cache file /data/data/[my application's namespace]/cache/com.android.opengl.shaders_cache: No such file or directory (2)
As my device is not rooted, I do not have access to the location and could verify the file exists, is corrupt, or has been deleted. I am not sure what the problem is. First of all, could the problems be related? It seems like a strange coincidence. To be clear; I do use a view holder pattern to optimise my ListView and it has worked just fine before so my implementation is an unlikely culprit.
Update As requested, here the code for my Adapter's getView method. While I don't believe it has anything to do with the problem, it worked fine before for about 5 months just fine, I am happy to cater to your questions.
#Override
public View getView(int position, View convertView, ViewGroup parentViewGroup)
{
final PersonaViewHolder viewHolder;
final Persona persona = provider[position];
if (convertView == null)
{
convertView = LayoutInflater.from(parentViewGroup.getContext()).inflate(R.layout.list_personas, null);
viewHolder = new PersonaViewHolder(
(ImageView) convertView.findViewById(R.id.persona_icon),
(TextView) convertView.findViewById(R.id.persona_description));
convertView.setTag(viewHolder);
} else {
viewHolder = (PersonaViewHolder) convertView.getTag();
}
Bitmap icon = BitmapFactory.decodeResource(parent.getResources(), persona.getPicture());
viewHolder.setIcon(icon, 50, 50);
viewHolder.setDescription(persona.getName() + " is a " + persona.getType() + "!");
return convertView;
}

As your probably are aware, having any type of actual processing in your getView() method should be avoided. While I can't speak to the cache file issue, I do notice you have the line:
Bitmap icon = BitmapFactory.decodeResource(parent.getResources(), persona.getPicture());
In your getView() method. You should consider implementing a LruCache to cache your bitmaps. Documentation on that can be found here:
http://developer.android.com/training/displaying-bitmaps/cache-bitmap.html
Additionally, on the line
convertView = LayoutInflater.from(parentViewGroup.getContext()).inflate(R.layout.list_personas, null);
You should not use .inflate(R.layout.list_personas, null); but instead use .inflate(R.layout.list_personas, parent, false);
Note the difference in the last arguments. This is the proper way to attach your view to it's parent. It may not improve performance, but it's correct.

HorizontalListView performance issues : Calls inflates for every subview

I'm making a Pulse kind of UI for my app. For this I'm using HorizontalListView class as given here. However, this class has performance issues and delivers a noticeable lag.
To confirm this I assessed it using TraceView Profiler and found that this class doesn't reuse views altogether and calls inflate() method for every call inside getView().
Here is how I'm designing the adapter:
public View getView(final int position, View convertView, ViewGroup parent) {
final BaseAssets baseAsset = baseAssetsList.get(position);
if (convertView == null) {
viewHolder = new ViewHolder();
convertView = inflater.inflate(R.layout.gallery_list_item, parent, false);
viewHolder.newLabel = (ImageView) convertView.findViewById(R.id.iv_new);
viewHolder.assetImage = (ImageView) convertView.findViewById(R.id.iv_thumbnail);
convertView.setTag(viewHolder);
} else
viewHolder = (ViewHolder) convertView.getTag();
}
class ViewHolder {
ImageView newLabel;
ImageView assetImage;
}
Am I doing anything wrong? If not, please suggest me workarounds to improve performance. Possibly some other library you would have tried or any way to reuse views in my current library. Thanks !

Seems like you're never calling convertView.setTag(viewHolder); in the case the convertView is null. You cant retrieve the ViewHolder without first setting it as the tag.
EDIT:
Other than that your code seems fine, my best guess would be that the problem lies in the implementation of the HorizontalListView.
I looked at its source (HorizontalListView.java) and if you can experiment with the source, try checking if mRemovedViewQueue is empty before it makes any calls to mAdapter.getView.If it is, then its not handling the recycling properly.

Issue when fast scroll a listview

I am working on a small project where I create a listview bound to an ArrayAdapter. In the getView() function of ArrayAdapter, I do a loading of images from web urls on thread, and set them to list items (based on position of course, so url[0] image is set to list_item[0] etc). It all seems to work well.
However when I was testing the app, I noticed that if I wait my listview to fully display, then perform a fast scroll back and forth, I see sometimes the image on one list item is misplaced on other (like being in an intermediate state). However it's not going away until I scroll the wrongly-displayed-item out of screen and then back.
I do not know if it relates to my loading web url using thread, or maybe loading image from local resource folder can have the same issue.
This actually leads to a question I have about getView() function. I think the logic is correct in my getView() because it's as simple as a binding of url to view based on position. And whenever getView() get a chance to be called, like when I scroll an item out of screen then back, it will make the list item display correctly.
The thing I do not understand is how to explain the issue that happened (like an intermediate state), and how to avoid it when writing code?
I paste my adapter code piece below, but I think the question maybe a general one:
#Override
public View getView(int position, View v, ViewGroup parent) {
ViewHolder viewHolder = null;
if (v == null) {
LayoutInflater inflater = (LayoutInflater) getContext()
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = inflater.inflate(layoutResourceId, parent, false);
viewHolder = new ViewHolder();
viewHolder.title = (TextView) v.findViewById(R.id.title);
viewHolder.description = (TextView) v.findViewById(R.id.description);
viewHolder.image = (ImageView) v.findViewById(R.id.image);
v.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) v.getTag();
}
listItem item = items[position]; //items is some global array
//passed in to ArrayAdapter constructor
if (item != null) {
viewHolder.title.setText(item.title);
viewHolder.description.setText(item.description);
if (!(item.imageHref).equalsIgnoreCase("null")) {
mDrawableManager.fetchDrawableOnThread(item.imageHref, viewHolder.image);
} else {
viewHolder.image.setImageDrawable(null);
}
}
return v;
}
}
static class ViewHolder {
TextView title;
TextView description;
ImageView image;
}

I have same issue when scroll quickly it alternate the vales of some item to others, just like background color of some items if changes randomly. I solved this issue by searching a lot and find exact solution is just adding these two methods in your adapter if you are using ViewHolder in your adapter
#Override
public int getViewTypeCount() {
return getCount();
}
#Override
public int getItemViewType(int position) {
return position;
}

Assuming that you are not caching the downloaded image.. lets see the following code:
if (!(item.imageHref).equalsIgnoreCase("null")) {
mDrawableManager.fetchDrawableOnThread(item.imageHref, viewHolder.image);
} else {
viewHolder.image.setImageDrawable(null);
}
Now if the image view is getting reused then it would already have the old image for the assigned list item. So until the thread download the image from the network it would display the old image and when the thread download the image for the current item it would be replaced with the new image. Try to change it to:
if (!(item.imageHref).equalsIgnoreCase("null")) {
viewHolder.image.setImageDrawable(SOME_DEFULAT_IMAGE);
mDrawableManager.fetchDrawableOnThread(item.imageHref, viewHolder.image);
} else {
viewHolder.image.setImageDrawable(null);
}
Or you can use something link smart image view that supports HTTP URI and also caches the images. Check out following link for smart image view:
https://github.com/loopj/android-smart-image-view
http://loopj.com/android-smart-image-view/

Add ImageLoader class from below link in your project.
link
just call DisplayImage() methode of Image loader class as below in getView()
ImageLoader imageLoader = new ImageLoader();
yourImageView.setTag(URL_FOR_Your_Image);
imageLoader.DisplayImage(URL_FOR_Your_Image,ACTIVITY.this, yourImageView);
Your images will load in background as you want without wait.

I think you should declare your downloader method fetchDrawableOnThread() as "synchronized" . Because a lot of threads are working simultaneously and any thread which started later, can end earlier. So there are chances of images being misplaced.
It happened to me for a long time. Finally "synchronized" helped me do it cleanly. I hope it helps you too.

I give it a try with synchronization again. Either synchronize the fetchDrawableOnThread(), or synchronize the global hashmap data within fetchDrawableOnThread(). First i thought the issue is gone, but when i tried more times later, i found the issue is still there.
Then i thought about the synchronization. fetchDrawableOnThread() is called from getView(), and getview() itself does not have a concurrency issue. Even if as Yogesh said, what happened INSIDE getView() is thread-based, and return early or late, it can not affect the correctness of getView(), i.e. the list item's display, only the sooner or later.
What i did(synchronization) inside fetchDrawableOnThread() i think it's still correct, 'cause i used a hashmap to cache images downloaded from remote url, and this hashmap is read/write upon in a multi-thread situation, so it should be locked. But i do not think it's the rootcause of the UI misplace, if hashmap is messed up, the image misplacement will be permanent.
Then i looked further on convertView reuse mechanism based on Praful's explanation. He explained clearly what happened when image always comes from remote and no cache locally, but my situation is i waited my list to display fully, i.e. all images download complete and cached complete, before i do the fast scroll. So in my experiment, the images are read from cache.
Then when inspecting my code, i saw one minor difference in the use of convertView as in getView() method, a lot of the example usages are like this:
public View getView(int position, View convertView, ViewGroup parent) { // case 1
View v = convertView;
.... // modify v
return v;
}
However the example i happened to copy from use:
public View getView(int position, View convertView, ViewGroup parent) { // case 2
.... // modify convertView
return convertView;
}
I thought it makes no difference at first, 'cause according to what android says, 'ListView sends the Adapter an old view that it's not used any more in the convertView param.', so why not use 'convertView' para directly?
But i guess i was wrong. I changed my getView() code to case 1. Boom! everything works. No funny business ever no matter how fast i scroll the list.
Quite strange, is convertView only old, or is it old & in-use? If the later, we should only get a copy and then modify..... ??

Remote Images in a ListView with ViewHolder pattern

Main question:
What is the most efficient bug free method of lazy loading remote images in a simple ListView adapter that utilizes the ViewHolder pattern?
I currently have an implementation that will first check a SoftReference Bitmap HashMap for a soft caches version of the image. If that fails I check my hard cache for a copy of the image. If that fails I get it from the web. I do all of this on a separate thread and in a queue to eliminate concurrent or duplicate downloads.
The problem is when loading through a callback. Because I utilize the ViewHolder pattern my views are constantly being recycled and I have not found a solid way to eliminate different images being randomly attached to my ImageViews. I do default to a default image before each load but because the views are being recycled so quickly "old" listeners apply onto my ImageView providing the wrong image which are then replaced with the correct image.
The only semi-solid solution I have found is to use the ViewHolder itself as the listener but this only makes the problem less apparent. It still happens on a fast scroll.
Any help would be appreciated.
Update:
https://github.com/DHuckaby/Prime

I have found a solution to the image switching problem and I will provide a code chunk below. I will not accept it yet though because I do not know if this is the most efficient method which is my original question. If this is implemented correctly it will work perfectly.
public void getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
...
String imagePath = insertImageUrlHere();
Object tag = holder.userThumb.getTag();
if (tag != null && tag.equals(imagePath)) {
// Do nothing
} else {
holder.userThumb.setTag(imagePath);
holder.userThumb.setImageResource(R.drawable.default_image);
AsynchronousImageLoadingUtility.load(imagePath, holder);
}
...
return convertView;
}
private static class ViewHolder implements AsynchronousImageLoadingUtilityCallback {
private ImageView userThumb;
#Override
public void onImageLoad(String source, Bitmap image) {
if (image != null && userThumb.getTag().equals(source)) {
userThumb.setImageBitmap(image);
}
}
}

Android listview image loading problem

I have an application that contains a couple of listviews. The listviews contains items that consist of imageviews and textviews.
All images are thumbnail sized on a server and the pattern used for loading them is like this:
Instantiate a DrawableManager
in the getView() method I do the following:
Pass the thumb uri and the ImageView instance to the DrawableManagers getImageAsync method
The method will first look on sd card if the image exists if so load it from SD card and save a softreference + update imageview drawable
If not exists on sd. Fetch from HTTP and save on SD (if there is enough space) put as softreference and update imageview drawable.
When the images exists on sd card everything works fine. But first time (or when using the app without sd card) the images seems to be populated into the wrong listviews rows when scrolling. When i stop scroll the problem fixes it self after a couple of seconds.
Its almost like if the ImageView references are pooled or something.
Any ideas?
I also include the getView method:
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder vh;
if (convertView == null) {
convertView = inflater.inflate(R.layout.informationrow, null);
vh = new ViewHolder();
vh.imageView = (ImageView) convertView.findViewById(R.id.rowInformationIcon);
vh.textView = (TextView) convertView.findViewById(R.id.rowInformationTitleLine);
convertView.setTag(vh);
}
else {
vh = (ViewHolder) convertView.getTag();
}
CustomCategory cc = items.get(position);
if (cc != null) {
vh.textView.setText(cc.get_name());
if (cc.getMediaUrl() != null) {
_drawMgr.fetchDrawableOnThread(cc.getMediaUrl(), vh.imageView);
vh.imageView.setBackgroundDrawable(getResources().getDrawable(R.drawable.imageframe));
}
else {
vh.imageView.setImageDrawable(getResources().getDrawable(R.drawable.trans4040));
vh.imageView.setBackgroundDrawable(null);
}
}
return convertView;
}

This is the View recycling used by ListView...
The convertView parameter passed to your getView() can refer to an existing item that has scrolled off the displayed part of the list, and can be reused to show an item that is now appearing.
So, yes, the same ImageView will be reused in multiple downloads in the code you posted. In your getView() you should check to see if a download is already pending and cancel it if it's no longer needed (or let it complete to a FIFO image cache somewhere, but not touch the ImageView which is now needed for a more recently-started download).
(An alternative, lazy developers implementation that assumes infinite memory would be to ignore the convertView parameter and instantiate fresh informationrow views on every call to it. Don't do that. :) ).

Use this Library for loading images in ListView.
https://github.com/nostra13/Android-Universal-Image-Loader