facebookarchive/Keyframes

Documentation: Explain about decoding JSON in the background

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#103 opened on Jan 12, 2017

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Description

Hey guys,

Using the Android library here. When loading large json files, I'm getting around a 2-3 second UI hang. This was obviously undesired and I narrowed down the issue to being in the deserialization of the asset from the InputStream. The way I got around the issue was by using an Rx chain and pushing the deserialization off of the UI thread while providing a Looper from a HandlerThread to the Scheduler. I'm sure this can be achieved in a similar fashion with AsyncTask if needed.

In general, the file still takes around 2 seconds to load while on a background thread. Our animation files are around 30k - 50k lines long.

Contributor guide

Tech stack
androidjava
Domain
mobile
Issue type
documentation
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic Android developmentknowledge of JSON parsingunderstanding of UI threading
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The issue asks for documentation on performing JSON decoding in a background thread to avoid UI hangs. The library loads JSON files, and the user experienced a 2-3 second freeze. To address this, examine the library's asset loading code, likely in the Android module (e.g., Keyframes/Android/...). Document how to use RxJava or AsyncTask to offload deserialization, referencing the existing InputStream handling. Note that the repository is archived, so any new documentation may need to be in a fork or separate guide.