Good approach to clean application data programmatically in Android - android

When I use RecyclerView and/or Picasso.
It seems to cache and store alot of data in my application.
However, I want to delete the stored data and the cache in a simple way whenever I am exiting my app.
What is the simplest way to delete all data stored in your created app programmatically?
What is the latest or the efficient way to tell Picasso to not store or cache images?

Picasso has evictAll() API to clear cache. Also you can set Picasso disk cache size to something small or zero.

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Persistent/Offline Image cache in Android

I am trying to figure out the best and the most efficient way of caching images to the disk, such that they would persist even after app is killed and re-launched in airplane mode. Consider the following use case:
Open the app and get all images and display them in their respective ImageView's
Kill the app
Put device in air plane mode
Open the app again.
I am trying to get the images to persist in an offline cache so that they can be displayed in the scenario mentioned above.
I went through documentation for picasso and glide and it wasn't exactly clear if their disk caching would work in this case.
Is there a way to do this using picasso or glide? I am trying to avoid having to write a custom implementation for storing this in SQLite etc.
Glide will do this for you by default without any extra work on your side. You can also customize what versions of the requested image to store in the cache.
One important thing you need to consider is if the URLs that you use Glide to fetch images from are available offline otherwise you will need to have some way to cache those as well so that you can initiate the Glide calls when you are offline.
You can see how I did it in this project: https://github.com/KhalafMH/popular-movies-android.git
To read about how to configure Glide caching see:
http://bumptech.github.io/glide/doc/caching.html

The best way to build cache

I have app that suits on Facebook, VK apps. I need to make a cache system to have offline access to some pages and improve a time of the data loading. I never make cache system earlier... So I very want to listen advices from people who built so systems. For example, how to save data better in database or in files. If it's database then where the best way to storage it in android app cache folder or use a simple built-in sqlite database... I will very glad to all answers by my theme.
You can cache items using the LruCache available in Android. LruCache
As you are trying to save Json objects, then the effective way is to retrieve the Json objects using a network library such as Volley and save the Json String in a SharedPreferences file. And you can parse it to load into a View whenever you want! And you can cache the Images using the NetworkImageView of Volley with LruCache! This helps you to cache and populate images and texts trouble free ! The perfect tutorial is already available here
Also, here is the code to my implementation as well!

Storing Images in android from web services

I am able to handle images and text from web URL's in android using AsyncTask, but have a separate question in mind.
Which approach is best suited for storing pictures for one time loading?
IE: Either in an SD Card or in SQLite DB.
If you want to store images for just one time loading, you don't need to store it in Sdcard. You better use a library like Glide or Picasso. It does all the hard work of caching and managing memory for you. It has very simple API.
Glide.with(this).load("http://goo.gl/gEgYUd").into(imageView);

Saving and retrieving images from internal or external memory in android

I want to save the images fetched from server for once and from next time i want to check first whether images are stored or not in device, if not then again it should fetch from server and store in user's device again, and if yes then application will use images directly rather than fetching from server again and again. It will be useful for enhancing the speed of application. Basically my application is fetching multiple images from server so i want to save those images on user's android device and from next time application should fetch from device. I think you got my question.
The simple way:
You can use Picasso.
It is a simple lib which provides image downloading and caching.
In my opinion it might not be the fastest, but it is pretty simple and intuitive. It does its job well and none who I asked complained about it.
Picasso
Other libs:
UIL
Volley
Glide
fresco
To make it short. There are lots of other libs. An awesome comparision of the most Populat ones can be found here and here
The do it yourself way:
You can also write you own caching logic with a LRUCache. Which is also pretty simple.
Take a look at:
https://developer.android.com/topic/performance/graphics/cache-bitmap.html
The LRUCache is just a Memory Cache so you might also want to use a DiskLRUCache

Android: Retrieve images from Server

I am building an android application which requires displaying images as a flip-view which will be retrieved from server. I have considered two approaches
Retrieving images from server URL and then displaying OR
Storing the image in db at server(MySQL) and then retrieving it from sq-lite on android application
My question is, which approach will be better considering everything (performance, etc.)?
Any other better approach is also welcome :)
This depends upon your Application and products you are going to display using Images, If they are not updated frequently then it would be better to use caching for faster user experience but if data is regulatory updated and previous data is keep getting filtered then always load using network.
Another approach you can just store latest 10-20 entries in your Database and as soon as you opens the application he can see some data and new data gets downloaded, this approach keeps users engage don't leave them your app just because every time they see loading.
For Image caching purposes there various good libraries avaible which are stable solutions for multiple images downloading as well as caching purposes E.g.
UniversalImageLoader, picasso, Volley
A good approach could be store locally images locally on demand, and keep it on cache, if the image changes on future you can invalidate your cache and download a new image.
I have used in a project a library that helps me a lot with to download the image in background, allows you also load image from cache automatically if stored previously or invalidate the cache. The library is android-query and here is an example of how you could use it.
You store images locally and load then to your app from local storage (This happens in a background thread)
You update the local storage by fetching the images in background, when needed, and then trigger the load from local storage (This also happens in a background thread)
This way you won get ANR's (application not responding) because of slow or missing internet connection, and you will be able to show images without connection at all.

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