Question

I’m developing for Android 2.2.

Things put to res and assets are compressed in the APK by default unless their extension indicates that they’re already compressed (mp3, png). Moreover, before Android 2.3, to assets, you could only put uncompressed files of size less than 1 MB.

Question 1:

if I put a 1.5MB binary file to res/raw, and my program refers to it with its standard Android ID (R.raw…..), then will the system pull the whole file into memory? Since the 1.5MB is stored in a compressed way, I suppose it must. This is unpleasant because it is possible that the program only needs 1KB of data to be loaded from a given file offset. This can have a serious impact on app performance/speed.

I see two solutions:

1. (hack) Use mp3 or png extensions; but I am not sure this allows memory-efficient access after all (i.e. inputstream.skipbytes, etc.)
2. After the installation, at the first start of the app, the app will copy the files to its own writable working folder (in SD card). Since this point, it will always access the files from there instead of the R.raw… way. Therefore, the sequential read will work for sure, i.e. the memory usage will be no more than the actual data read from the specified file offset (apart from temporary read buffers used by inputstream.seek implementation, which are well-optimized i.e. small I suppose).

Question 2:

what is the best way of reading binary data memory-efficiently, from big files? I don’t want to split my big files into many small ones unless that’s the only way.

Answer 1

I’d go with #2 solution and then would use RandomAccessFile to avoid linear access.