Develop Reference

How to reduce Android app size by compressing images?

I am developing an Android app which has hundreds of .jpg files (over 300) each one of around 40kB. I would like to know if there is a way of reducing the size of my app. I looked at a similar question here Reducing Android App Size, but the problem still exists. Is there perhaps a way to compress the images and decompress them in real time when needed, or any other way to make my app more space efficient while not sacrificing speed?

If you have used tinypng for every resource you did your best with this kind of solution. In general, it's better to use vector graphics where the general icon will be <1kb. Also, a vector resource can be animated. If it's quite simply bitmaps, you can generate them in code on demand. Also, you can divide your app by dynamic features and each will be downloaded on demand with their part of the resources.
Is there perhaps a way to compress the images and decompress them in real-time when needed?
There is no standard Android solution out of the box. Probably, you can write something on your own. But this looks like too much effort.
Still, the most practical solution: use vector graphics as max as possible, generate in code what you can generate, compress with tinypng the others. That should be enough or you should have a very good reason for making some extra work.
For more info about vector graphics in android. For standard vector graphic import right in the android studio.
Web-site where you can download icons and insert them into the project.

Limit apps cache size in Android

Is there anyway to limit the cache size of a certain application in Android, not the entire OS cache?
I don't want to manually delete cache directory every time.

Please take a look at this answer: https://stackoverflow.com/a/2863141/2101822
He said :
There is no per-application limit for the cache directory.

Android application's cache

What data is stored in application's cache directory? I'm not using it in my application and I still can see its size grows. Is it webview caching images? HttpClient storing some data? What else?
Can I erase it's contents safely from code at any time?
Thanks in advance

Android can clean the cache up whenever it's running low on space, so the assumption for whatever application using cache files should be that they can be deleted at any time. In other words, if you're using some other modules that create the cache in your application, you should be able to delete those files safely at any time, assuming those modules are well coded. What it will do to performance, that depends on many more things.
Maybe just keep the size under control, so delete the older files when you feel it gets too big? I think Android recommends 1MB for cache.

Smaller APK size with large assets?

I am creating a simple android app to view a comic book. The pages are large(0.5-1 mb each), high quality .png's and I am loading them into a webview to make use of the built in zoom controls. So far I only have 17 files and the APK size is already about 16 mb. I'm looking to add over 200 files in future updates. I can't really reduce the quality too much because there is small text that must be zoomed-in on to read. Any suggestions? A similar question was posted here: How to reduce App (.apk) Size, but I don't want to lose the quality of the images. I'm not sure if it's appropriate to link to here, but you can have a look at my app by searching for Tracer (by Detour Mobile) on the android market if it helps at all. Thanks in advance.

You could compress them without using lossy compression- e.g. zipping/rarring them, but I don't believe this would gain you much more than a few kilobytes here and there. Otherwise, try using a more compact format than PNG, such as JPEG (you won't lose too much quality.) By the way, all of this was suggested in the referenced post.
If you do decide to scale down the images' size somewhat, be sure to use a method like bicubic sharper- it tends to look better than others when reducing image size.
Another option would be to download the images for the comic that is being read on-the-fly with pre-fetching so reading would not be interrupted as much.

Consider placing your images in Assets folder as opposed to Res. The big difference is, Assets content won't be compiled into R.java class so you will see major storage savings. You'd have to modify your code though as you won't be able to call up the images via the regular r.resID notation, but it's doable

android offers a new way to deal with it.
android app bundle apk size has a maximum size of 150mb
but you can use an asset pack to seperate the apk from the static files
and upload your app
here is a more detailed explanation about asset packs:
https://developer.android.com/guide/playcore/asset-delivery
here is the guide for integrating asset packs with regular android app:
https://developer.android.com/guide/playcore/asset-delivery/integrate-java

Best Practice when Caching files in Android

I currently have my app caching image files in the cache sub-directory for the application. The images are used in a ListView and stored in a HashMap of SoftReferences to Bitmaps.
So my question is this, what is the best way to cache these image files without inflating the space my application uses AND remains responsive from a user standpoint.
Things I am concerned about:
I know the user can clear the cache and that it is done automatically when space is low on internal memory, but I feel most users will see a several MB app and uninstall it. Also if the space is constantly low, my app will just keep downloading the images, making it appear slower.
Most devices have an SD card pre-installed, but what should I do when it is not inserted? The SD card may also be slower compared to internal storage, affecting my app's performance.
Should I include an option to choose the location of the cache?
Should I attempt to manage the size of my cache (be it in the /cache or /sdcard) or just forget about it?
Thank you for your time (its a long one I know) and please post any relevant experience.

I can't offer you a comprehensive set of best practices, but I can offer what I've learned so far:
Managing your cache is a good idea. My app's cache is such that I know that I'll never need more than a certain number of cached files, so whenever I insert a new file into the cache, I delete the oldest files until I'm under the limit I have set. You could do something similar based on size, or simply age.
Caching to the SD card, if it's available, is a good idea if your cache needs to take up a lot of space. You'll need to manage that space just as carefully, since it won't automatically clear that space for you. If you're caching image files, be sure to put them in a directory that begins with a dot, like "/yourAppHere/.cache". This will keep the images from showing up in the gallery, which is really annoying.
Letting the user choose the location of the cache seems like overkill to me, but if your audience is very geeky, it might be appreciated.
I haven't noticed a much of a penalty when caching to the SD, but I don't know how your app uses that information.

Everyone has good ideas. I like the idea of using SoftReference's, although I'm not sure how often those get cleaned up, as this varies so much from VM to VM. You might want to combine that with regular HashMap to prevent you entire cache getting cleared every few minutes.
EclipseLink has a few different cache implementations and pretty good documentation on them. You could probably take advantage of a few ideas from the implementation (e.g., LRU, MRU, etc.). e.g.,
hard cache
soft cache
combined hard/soft cache
Since you're tuning a cache down to the nitty-gritty, I would recommend tuning it to different devices based on the hard specs. This is normally bad design, but the scope of the hardware that your software runs on mandates it, IMHO. e.g.,
Detect the amount of available memory on the SD card. Most new smart phones come with multi-GB SD cards, and those are pretty hard to fill up with regular usage for most users. Use away! You can also detect the amount of space available on the SD card on startup, and increase/decrease the size of your cache on startup.
Detect the amount of available memory and configure your caches with that in mind. If a user is using a hardware-intensive application, I don't think they'll mind that it makes up 200MB of RAM and provides a very fast user experience, especially since they spent a lot of money to have a phone that has 1-2GB RAM.
Good luck!

Should I include an option to choose the location of the cache?
IMO: No, let make it more simplest as possible (Except you can include advance setting for expert user)
Should I attempt to manage the size of my cache (be it in the /cache
or /sdcard) or just forget about it?
IMO: This is optional, it is double sword: your more work on background will help user more convenience but also more bug prone
Use 3rd libs:
IMO using 3rd library as Picasso is better, it handle cache automatically by order: Memory cache -> Disk cache -> Network