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.
Related
I am currently storing bitmap images inside my cache, each bitmap can be upto 3mb in size each. I am using getCacheDir() however, after reading androids documentation, I found this:
Note: you should not rely on the system deleting these files for you; you should always have a reasonable maximum, such as 1 MB, for the amount of space you consume with cache files, and prune those files when exceeding that space.
So I am considering switching my cache to using getExternalCacheDir(), but I am abit uncertain about this:
The platform does not always monitor the space available in shared storage, and thus may not automatically delete these files. Apps should always manage the maximum space used in this location. Currently the only time files here will be deleted by the platform is when running on JELLY_BEAN_MR1 or later and isExternalStorageEmulated(File) returns true.
I would like to have full control of the cache dir, because if files are randomly deleted this could really affect the running of my application. I have already set an upper limit for the size of the cache so it will never exceed a certain amount of space. How can I now prevent the system from monitoring and deleting from this cache as it pleases?
thanks
Don't think that cache is permanent storage. You mustn't store there files that you rely on. Cache used for storing data that you don't really want to reload or recreate, but you can do it if needed (as with loading pictures from web. Much faster to load from disk, if already done, but can be done without it). If you really depend on this files use getFilesDir() this will route you to specific app directory, that wouldn't be erased if no memory (but still can be erased by user in settings). Also, if you have data that is static and you need it always, you must store it in the assets folder, all other data must be considered as temporary (any time user or system can erase it) and checked for existence.
I´m working in an App which does have images that are used quite often, however there are others download used only once.
Does Glide have any way for deciding on the fly which images should be stored only in Disk or only in memory?
As far as I´ve seen it does the cache depends on the configuration buy I´de like to be able to say by myself which ones should be in disk and which ones no.
You can use .diskCacheStrategy() to manually control whether and how an individual request is cached on disk and skipMemoryCache() to control whether an individual request is cached in memory.
I have a rather large SQLite database (~20 mb) I need to access from my Android Xamarin-Forms app.
Everything online I've read says you can read the database by copying it to the filesystem first. For example, this question. However, won't that mean the large database is duplicated, wasting users' precious space (and nearly doubling the footprint of my app)?
There must be a way to read the SQLite database directly from the assets, or use some other method to bundle the database with my app that won't waste so much space. But how can I do this?
You don't want to use it from assets, even if you could, because assets is a compressed read only file, part of your installation. You can't write updates into it, which kills 90% of database use. And its inefficient for reading as its zipped up. So you really do need to copy it. If you're worried about disk space, consider downloading it from the web rather than keeping it in your apk.
I am new to android and I was wondering what the correct way is to manage and set some maximum limit for your application's data storage. For instance, I have an image cache and a database file with some information. I do not want it to potentially become extremely big. Is there a built in a way that android provides so I can manage the size of how much data is stored? Thanks again
I don't think so. You will have to manually do that. Your image cache would have a database and a cache folder. So, there is no custom method or class that you could use to set limits to the DB or the folder.
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