Develop Reference

Displaying images in a Recyclerview

I have a recyclerview that I want to display images that I have saved in drawables in jpeg. For loading I was using an Async Task, but this doesn't preload or Cache them. I was told to use one of the tools like fresco or glide to do that, but which one can do the Job better?
The most important thing for me is that the app doesn't crash, but it would also be nice to be able to preload certain images already before the View is displayed and afterwards preload as many as memory allows.

You can use Fresco for this. An example for a recycler view that loads images from the network can be found here:
https://github.com/facebook/fresco/blob/master/samples/showcase/src/main/java/com/facebook/fresco/samples/showcase/drawee/DraweeRecyclerViewFragment.java

Download image as thumbnail in listview adapter android

I have a decent android app which is using two fragments one of them is Listfragment. And my question is, can I use Asynctask to download the image and compress it to a thumbnail and then assign it to an imageview ? (Imagine there are like 100 items in ListView). Or is this even possible to call the asynctask each time ?

You don't need to reinvent the wheel. There are libraries which already can download, cache and resize image for you. For instance Picasso:
Picasso
.with(context)
.load(url)
.resizeDimen(width, height)
.centerCrop()
.error(R.drawable.error_img);
.into(placeholder);

For this task, I would strongly recommend the use of an external library.
There are many to choose from that can be used to download, display and cache images from an online source. As many of these libraries have been developed for many years, they are usually going to be better than any bespoke code you write.

How to handle Android ListView having more than 15000 bitmaps of size 100kb

I am getting URL string of image in one response, Then i am downloading those images and converting tobitmaps then displaying in listview.
Here my question is in future listview items may increase upto 50000,in this case how can i handle data in listview for smooth scroll without giving ANR Exception.Please provide some sample code.

Dont Load All Images At a Time.... It will cause OutOfMemoryException..you can load images in number of pages from URL....
To download images from URL you can use Picasso library...
It helps you to avoid OutOfMemoryException and store cache of images too..
You can use LAZY LOAD... and you can try this code for download images...
Picasso.with(context).load(URL).fit().centerCrop().into(imageView);

Simple answer dont make a listview so big. 50K elements in a single screen is never a good idea in any scenario(web, desktop or mobile). My suggestion is to have some sort of pagination just like in websites. As for the images like #Prag suggested above use lazy loading for showing images. In my app I used Universal Image Loader and find it extremely useful for showing a large number of bitmaps.

Downloading image from web takes too much of time in Listview

Hi in my application i need to download some images and text from the web and need to display in listview. for that i'm using POJO class means initially storing all the images in to the POJO class and then display in listview
It is good for less images but while downloading more than 100+ plus images it taking too much of time to load,
can anybody suggest some good solution for this.

You can use the following libraries which are able to do lazy loading :
UrlImageViewHelper
Universal Image Loader
Picasso
All these libraries are lazy loading ready which means these libraries can reuses views in widgets like ListView and GridView.

Try to use AsyncTask() method.Since it is doing its process in background it may work quicker.

Android ListView with lots of same drawables performance

I'm developing an Android app with a list view that contains lots of drawables.
Most of them are the same so I'm trying to use a HashMap that returns the same allocated bitmap when it's needed but still there are lots of allocations and GC actions so that the list gets stuck from time to time when scrolling.
What can I do to optimize the performance in such case?
Caching method - loadImage Using google code
mImageWorker.loadImage(pic_url, holder.pic);
holder.*some bitmap*.setImageBitmap(Utility.getBitmap(context, id); //can be one of 5 bitmaps do I use caching with a hashMap

see this example
this will helps you....
don't put so much process under the getView() method . this will lack the listview scroll performance
if you want to do image crapping or drawable to bitmap conversition or anything .. just do all process
before loading adapter.. and just assign values for each row in getView()...

Try to use lazy loading technique using caching, you can find many tutorial on the web:
You have to see this SO thread
Also see this:
Multithreading For Performance, a tutorial by Gilles Debunne.
This is from the Android Developers Blog. The suggested code uses:
AsyncTasks.
A hard, limited size, FIFO cache.
A soft, easily garbage collected cache.
A placeholder Drawable while you download.

If you want to optimize the code, try lazy loading concept for loading images in list. Please refer: Lazy Load images on Listview in android(Beginner Level)?