So I have been struggling with the best way to load images in a ListView in Android for a while.
The images come from a server, so can take some time to load. From what I understand there are only 2 ways to implement this:
1 - Load the images on the main thread - This leads to have the correct images display immediately when the view displays and scrolls, but gives poor scrolling performance and can lead to the app hanging and crashing.
2 - Load the images in an AsyncTask. This means the images will be blank when the list display or scroll, but eventually display. Because of caching done by the list, you can also get the wrong image for an item. But this gives good performance and scrolling, and does not hang/crash.
Seems like neither solution works correctly. There must be a solution that works?? I have seen other posts like this, but the answer seems to always be 1 or 2, but neither is a good solution...
My code for the list adapter is below.
The HttpGetImageAction.fetchImage() method either executes an async task, or fetches the image on the main thread depending on a flag I set. I also cache the images locally and on disk once they have been loaded, so the issue mainly occur the first time (but the cache is only for 100 images, and the list has 1000s)
public class ImageListAdapter extends ArrayAdapter<WebMediumConfig> {
Activity activity;
public ImageListAdapter(Activity activity, int resourceId, List<WebMediumConfig> items) {
super(activity, resourceId, items);
this.activity = activity;
}
class ImageListViewHolder {
ImageView imageView;
TextView nameView;
TextView descriptionView;
TextView statView;
}
public View getView(int position, View convertView, ViewGroup parent) {
ImageListViewHolder holder = null;
WebMediumConfig config = getItem(position);
LayoutInflater mInflater = (LayoutInflater)this.activity.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
if (convertView == null) {
convertView = mInflater.inflate(R.layout.image_list, null);
holder = new ImageListViewHolder();
holder.imageView = (ImageView)convertView.findViewById(R.id.imageView);
holder.nameView = (TextView) convertView.findViewById(R.id.nameView);
holder.descriptionView = (TextView)convertView.findViewById(R.id.descriptionView);
holder.statView = (TextView)convertView.findViewById(R.id.statView);
convertView.setTag(holder);
} else {
holder = (ImageListViewHolder) convertView.getTag();
}
holder.nameView.setText(Utils.stripTags(config.name));
holder.descriptionView.setText(Utils.stripTags(config.description));
holder.statView.setText(config.stats());
if (MainActivity.showImages) {
HttpGetImageAction.fetchImage(this.activity, config.avatar, holder.imageView);
} else {
holder.imageView.setVisibility(View.GONE);
}
return convertView;
}
}
You should never load images on the main thread. Any network calls should be done asynchronously and should not be done on the main thread. Your images might load quickly (on the main thread) because you may have a good internet connection, have small images and/or have few images. But imagine what would happen if someone using your app has a slower internet and then one day your list grows to hundreds!
The approach below is a well accepted practice for loading scrollview content
a) load your text content as you load the scrollview. Again the loading should be done async but you can show a loading view until the download completes
b) Show image
placeholders while the image loads on each cell
c) Load the images
asynchronously
Using a library such as Picasso would help immensely because there is a lot of boilerplate code which you'd need to handle otherwise such as
cancelling image download when a cell is reused and
starting a new download for a reused cell
caching
retrying a failed download
Hope this helps.
Use Glide [https://github.com/bumptech/glide] or Picasso [http://square.github.io/picasso/] - both libraries are very similar, and easy to use, have caching, work in background, allow placeholders ets.
Usage is as simple as:
Picasso.get().load("http://i.imgur.com/DvpvklR.png").into(imageView);
Simple Solution: Glide.
Glide is a fast and efficient open source media management and image
loading framework for Android that wraps media decoding, memory and
disk caching, and resource pooling into a simple and easy to use
interface. Glide supports fetching, decoding, and displaying video
stills, images, and animated GIFs.
You can load the image like:
GlideApp.with(context)
.load("http://via.placeholder.com/300.png")
.into(imageView);
Refer for more info:
https://guides.codepath.com/android/Displaying-Images-with-the-Glide-Library
https://github.com/bumptech/glide
Use Glide library.. Its recommended by Google.
Step 1:
Use latest Glide Version 4 dependency (https://github.com/bumptech/glide)
implementation 'com.github.bumptech.glide:glide:4.8.0'
annotationProcessor 'com.github.bumptech.glide:compiler:4.8.0'
Step 2:
Glide.with(MainActivity.this)
.load(url)
.apply(new RequestOptions().placeholder(R.drawable.placeholder).error(R.drawable.error_image))//this line optional - you can skip this line
.into(imageview);
use picasso or Glide Library
What these library do , is that they image url from u and download them and save it in cache so that whenever you open the same image another time it will load faster and it prevents the usage of the network
Picasso
http://square.github.io/picasso/
Glide
https://github.com/bumptech/glide
You can try UnivarsalImageLoader which is quite Fast and Optimised.
It supports Multithread image loading (async or sync) and high level of customization.
https://github.com/nostra13/Android-Universal-Image-Loader
Here's how I do it
First I always create the RecyclerView.ViewHolder to which I pass a Func<int, Bitmap> image_provider (or you can pass some sort of lamda?) which when called will retrieve the image for a specific Id, if it can't it will show the default loading image
Everything is stored in a fragment (which I call a DataFragment) which has retainstate set to true.
First load a list of json objects that tell me which images I must show, this happens inside the data fragment so it will go on if there is a configuration change
I send that info to the adapter using a method like SetItems(MyImages)
Then I start a new thread that will load the images (while allowing the user to work)
I do this with the TPL library, the closest approximation for Android is Anko Async but you can also do it with AsyncTask, the problem is that I send a lot of messages to the main thread, so to do it with AsyncTask you have to give it a handler to the main thread which will send messages.
In the thread I loop through all the images I have to download, and download them and send a message to the DataFragment which sends it to the currently attached Activity which triggers the NotifyItemChanged method in the adapter
The adapter on creation receives a Func<int, Bitmap> image_provider which it invokes and retrieves the image from memory
I know it sounds a bit messy, so if you want code examples I can give them , but they are in C#
In your app level gradle implement below repository:
implementation 'com.squareup.picasso:picasso:2.5.2'
Put below line where you want to load image
Picasso.with(getApplicationContext()).load(config.avatar).into(imageview);
just use Picasso.get().load("http://i.imgur.com/DvpvklR.png").into(imageView); or
Glide.with(getApplicationContext()).load("image_url").asBitmap().centerCrop().into(new BitmapImageViewTarget(imageView)
in adapter like any view and done no extra efforts required
Related
Have you ever been going through apps like 9gag, Instagram or Facebook? You notice, that while scrolling the pictures load into the recviewer. They sort of come in one by one while you can still use the app.
I have implemented my own custom recviewer and am stuck right here:
pictures = KumulosHelper.Pictures.getNewestXPhotosFromUserInRange
(strUsername, "6", startNumberOfTask.ToString(), "1");
foreach (var picture in pictures)
{
startNumberOfTask++;
var metrics = Resources.DisplayMetrics;
lstData.Add(new DataForProfile()
{
imageId = startNumberOfTask,
img = (Bitmap.CreateScaledBitmap
(KumulosGeneral.DecodePhotoFromBase64(picture.photo),
metrics.WidthPixels, metrics.WidthPixels, true)),
description = picture.taskId.ToString()
});
}
Where I type in "6" is where I get 6 pictures to load into my recycle viewer form the server. I can type in 10 or 20 and it continues loading those pictures. So, I could probably set up a "reachedbottomevent" to continue loading new pictures when the viewer reached the end. But that would mean that the user has to wait everytime he or she reached the bottom of the matrix. This is pretty annoying. Also, the whole activity wont start untill all pictures are fully loaded.
How do I get my recview to behave like the afforementioned apps above? Some sort of "smart" loading the pictures?
Thank you for the input!
Try using the Picasso library which is very reliable and easy to use. It also loads pictures in a background thread.
https://www.nuget.org/packages/Square.Picasso/
Also, the whole activity won't start until all pictures are fully loaded.
In order not to block your UI thread try using a BackgroundWorker or a Task.
At last, if you want to load a new batch of images before the user reaches the bottom of your list, then change your logic to trigger the call for a new batch for example when the user scrolls half the table.
Question may seem weird but I ran in an issue with Android app. I am creating views for my Android app dynamically using layout inflater and the view contains images. Most images are less than 800kb. So when I open the app, it starts using tons of RAM and when I switch to another activity, it adds more ram which contains images too. When I exit the activity and come back to the first activity it is not cleaning the RAM. I cannot add my actual code here because of the company policy but here is the snippet of what I am doing,
I have two activities HomeActivity and DisplayActivity. In home activity I have empty scrollview. I am making db query an pulling information. Using layout inflater,
for (DataModel d : dm) {
JSONObject dataJson = new JSONObject(d.getData());
View headerCard = LayoutInflater.from(HomeActivity.this).inflate(R.layout.head_card, null);
ImageView cardHeadImage = (ImageView) headerCard.findViewById(R.id.head_card_header_image);
TextView cardNote = (TextView) headerCard.findViewById(R.id.head_card_note);
String imageLink = dataJson.getJSONObject("data").getString("article_image");
String note = dataJson.getJSONObject("data").getString("article_title");
imageLoader.displayImage(h.getMediaURL() + imageLink, cardHeadImage);
cardNote.setText(note);
scrollViewChild.addView(headerCard);
}
So when I don't add images, it is using less RAM. I have cached images. So my question is that is there anything possible to clear RAM after view is generated and placed in display? I can provide more information if needed. But basically this is how my both activities are running.
The imageLoader works in three steps. 1) Check for cached image. 2) If image is not cached than download image and cache it. 3) Display image in imageview. 2nd step will be skipped most time as images are mostly available from cache.
Thanks. :D
I have a ListView extending ArrayAdapter. I am using a view holder patter for the getView and here is a part of my getView method which loads images using picasso. The following code is expected to load images into my image view inside every list item.
Picasso.with(mContext).load(imageURL).fit().into(holder.myImageView,
new Callback(){
#Override
public void onError() {
holder.myImageView.setVisibility(View.INVISIBLE);}
#Override
public void onSuccess() {}});
So here is the problem: this works fine for OS < Android 5.0, but in the case of Android 5.0 (Lollipop), it looks like Picasso is fetching these images when my app is installed and run for the very first time, but when I launch the app again, the images don't load. Not at all sure what the problem is. I am not loading huge images, you can assume all the images that I am loading are only of the size of a small icon/thumbnail (around 120X120). I am using Picasso 2.4.0 for my application and the phone that I am using for testing is the Nexus 4.
Open Issue as of this edit: https://github.com/square/picasso/issues/633
Alternative:
I struggled to find an answer for very long time yesterday night. I explored Picasso really intimately trying several stuff. None did work. So right now what I am doing is:
if(api>=21) //Keeping in mind about any updates beyond 21
Use Android-Universal-Image-Loader
else
Use Picasso
For more information on Andorid Universal Image Loader.
Please visit https://github.com/nostra13/Android-Universal-Image-Loader
Its awesome with its cusotmization.
Agian, dont get me wrong, I am 100% +ve there is a solution with Picasso, I am sure I will find it someday, I will post it here then, but for anyone who have problems like me, I think the above is the way to go. Please suggest if you have anuy other better way.
************************ ISSUE FIXED **************************
https://github.com/square/picasso/issues/632
https://github.com/square/picasso/pull/860
************************** ISSUE FIXED ****************************
I have been using Picasso for quite some time, but I had to upgrade OkHttp library to 2.0.0 and, consequently, I had to upgrade Picasso to version 2.3.2.
However, now Picasso does not load any image at all, the imageviews are left empty. No error shows up at any time, but when I turned Picasso logging on, the "Hunter" seems to be dispatched and starts executing, but never finishes.
All the images are accessible and rather small (around 200px by 100px).
I'm loading the images through Picasso's "typical" method:
Picasso.with(context).load(url).error(R.drawable.errorimg).into(imageView);
However, the errorimg is never shown.
What could I be doing wrong?
EDIT:
Here is the code of one of the places where Picasso is not working (PlaceListAdapter.java - getView function)
public View getView(int position, View convertView, ViewGroup parent)
{
final PBNPlace ev = values.get(position);
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(R.layout.places_list_item, parent, false);
TextView titleView = (TextView)rowView.findViewById(R.id.place_title);
ImageView placeImage = (ImageView)rowView.findViewById(R.id.place_image);
Picasso picasso = Picasso.with(context);
picasso.load(ev.imageURL).error(R.drawable.chat).into(placeImage);
titleView.setText(ev.name);
return rowView;
}
When you upgraded OKHttp, did you also upgrade the okhttp-urlconnection dependency?
I had this issue and it turned out I was still calling for version 1.6.0 of okhttp-urlconnection in my build.gradle file. There were no error messages that made it readily apparent to me that I had overlooked this.
Changing that to 2.0.0 solved the problem.
Picasso does not have an HTTP client inside of it so saying that is "supports HTTPS" means little.
When you pass in a url (whether it has a scheme of http:// or https://) we pass that along to the most appropriate HTTP client there is.
Maybe that's java.net.HttpURLConnection. Maybe it's that sexy bundle of bytecode OkHttp. The bottom line is that whatever the scheme is we just let the HTTP client handle it.
Any problems you are having with http:// vs https:// are in the configuration of the client, not Picasso.
Said By JakeWharton
So for loading images you just need to add below dependencies in your gradle file.
compile 'com.squareup.okhttp:okhttp:2.2.+'
compile 'com.squareup.okhttp:okhttp-urlconnection:2.2.+'
compile 'com.squareup.picasso:picasso:2.5.2'
Reference : https://github.com/square/picasso/issues/500
<uses-permission android:name="android.permission.INTERNET"/>
this might be the stupidest answer but sorry for that. Sometimes small things are what we forget. Have you checked your permission.
I am using volleys NetworkImageView to load image´s in an ArrayAdapter.
For some Items in my Adapter i want to use a Drawable resource instead.
Unfortunally setting the ImageResource doesnt seem to have an effect on NetworkImage.
networkImage.setImageResource(R.drawable.mydrawable); // no effect
I tryed working without NetworkImageView using an ImageLoaders get() method providing an interface. Unfortunally the view recycling didnt work out anymore and image downloads overrode already recycled and reused views.
ImageLoader.ImageListener listener =
ImageLoader.getImageListener(image, R.drawable.loading, R.drawable.error);
ImageCacheManager.getImageLoader().get(url,listener);
// Override´s recycled views image
Any solutions?
If you only want to show drawable and not load any image at all for specific item, this is quite easy:
public void bind(Item item) {
if (item.shouldDisplayDrawable()) {
imageView.setDefaultImageResId(R.drawable.my_drawable); // show your drawable
imageView.setImageUrl(null, app.getImageLoader()); // and if url == null, Volley will not load any image to replace Default
} else {
imageView.setImageUrl(item.getImageUrl(), app.getImageLoader()); // load image from url
}
}
I tried this in my Adapter, recycling works without any issues. And you can continue using
imageView.setDefaultImageResId(R.drawable.icon_image_default);
imageView.setErrorImageResId(R.drawable.icon_image_error);
on imageView you download from url, it will display correct drawable while loading and on error.