Add an option to control the mails cache size

[DenBond7]

#668 #585

[DenBond7]

@tomholub I need to know your opinion. Currently, the app uses a cache which uses DiskLruCache. The cache size = 50Mb. I think for the first time that's enough. As for me, it'll be better to move that to the next releases. In this issue, I was going to add UI, where a user can change the cache size. But maybe it's redundant for the current realization. Maybe 50Mb it's enough for most cases.

[tomholub]

I was going to ask you about this. How is the cache saved - does Android system know what this is deletable cache? If I go to android settings -> flowcrypt -> delete cache, will the cache get wiped?

[tomholub]

Also, do the oldest unused cache records automatically get replaced with the new ones to stay under 50mb?

[DenBond7]

@tomholub

How is the cache saved - does Android system know what this is deletable cache? If I go to android settings -> flowcrypt -> delete cache, will the cache get wiped?

No, the cache won't wiped. I use the private app directory to store the cache. I use getFilesDir() to get a directory. Then this cache can be controlled only by app.

Also, do the oldest unused cache records automatically get replaced with the new ones to stay under 50mb?

Of course, it's how LruDiskCache works

[DenBond7]

Least Recently Used (LRU)

[tomholub]

Is there no way we can store the cache in a place that Android can understand and delete as needed, while still using LruDiskCache?