Unless you are writing a Download Manager, downloading files in an Android
application is never going to be the main business logic to solve but based on
the requirement, you may need to download metafiles, media files, or documents
over the Internet within your Android application. However, a reliable
solution to download files in an Android application poses its own challenges
including but not limited to the following list:
1. Thread Management
IO operations must be executed in a separate thread. Though there are plenty
of options to achieve this such as now deprecated AsyncTask, Kotlin coroutines, or RxJava, still complex for a novice developer to properly handle
the concurrency problems. Sending signals to the downloading thread to cancel
or pause the download may introduce additional synchronization issues.
2. Error Handling
What if the Internet connection dropped while downloading the file? What if
the application is closed while downloading/saving the file? How to handle all
HTTP errors? the list goes on. Addressing all these scenarios is tedious and
most of the time not possible.
3. Updating the UI
While downloading the file in a separate thread, updating a progress bar in the main thread is a challenge unless the concurrency framework you use provides an easy way. The same goes to update the UI after the file is downloaded.