Android OutOfMemoryError - Loading JSON File

Question

The app I am working on needs to read a JSON file that may be anywhere from 1.5 to 3 MB in size. It seems to have no problem opening the file and converting the data to a string, but when it attempts to convert the string to a JSONArray, OutOfMemoryErrors are thrown. The exceptions look something like this:

E/dalvikvm-heap( 5307): Out of memory on a 280-byte allocation.
W/dalvikvm( 5307): Exception thrown (Ljava/lang/OutOfMemoryError;) while throwing internal exception (Ljava/lang/OutOfMemoryError;)

One strange thing about this is that the crash only occurs every 2nd or 3rd time the app is run, leaving me to believe that the memory consumed by the app is not being garbage collected each time the app closes.

Any insight into how I might get around this issue would be greatly appreciated. I am open to the idea of loading the file in chunks, but I'm not quite sure what the best approach is for such a task.

Thank you

Answer 1

When you say "2nd or 3rd its run" do you mean each time your starting with a fresh emulator? or do you mean leaving the application and coming back? (for instance pressing home, or calling finalize() )

If your referring to leaving the application and re launching it:

if you haven't set android:launchMode in your manifest to define the activity as singleInstance or singleTask then each time the application is launched a new activity is created and added to the activity stack. You could easily have multiple copies of your activity running in your application process eating a lot of memory.

If its happening the 2nd launch your still using aa lot memory and should break it down more.

Answer 2

One strange thing about this is that the crash only occurs every 2nd or 3rd time the app is run, leaving me to believe that the memory consumed by the app is not being garbage collected each time the app closes.

That is certainly possible, and if it is the case then it probably due to a memory leak that can be traced back to something that your application is doing. I think you should focus your initial efforts into investigating this aspect ... rather than loading the file in chunks. (I am not familiar with the Android tool-chain, but I am sure it includes memory usage profilers or memory dump analysers.)

EDIT

In response to your followup comment, the fact that it works 2 times in 3 suggests that your app ought to work roughly as-is. Admittedly, you don't have much leeway if the input file gets bigger.

A couple of ideas though:

• Rather than reading the file into a String and running the JSON parser on the String, use a parser that can read directly from a stream. Your current solution needs space for two complete copies of the data in memory while you are doing the parsing.

• If the file gets much bigger, you may need to think of a design that doesn't create a complete in-memory representation of the data.

I'm not sure that it is a good idea to read a JSON file in "chunks". This could present problems for parsing the JSON ... depending on exactly what you mean by reading in chunks.

EDIT 2

Maybe what you need is a "SAX like" JSON parser; eg http://code.google.com/p/async-json-library/

Answer 3

Try to use parse JSON Data Efficiently on Android, using JsonReader. It's like SAX parsing for XML.