Question

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I need a good way to get data from a thread to another activity.

I have one gaol: how to develop an Android app that plots bluetooth data forever in real-time.

I inherited a background thread which updates the screen with new data it receives over a bluetooth connection. When I launch my Plot activity I can see a bluetooth background thread continue to write bluetooth data to Logcat forever and ever. So I know for a fact the bluetooth background thread is still running when I launch my Plot activity.

I have succeeded as follows: since this bluetooth background thread seems to run fovever, I decided to use its update() method to call my static Plot.plotData() method to plot the bluetooth data. And this works. It will will run endlessly with out a problem – receiving bluetooth data and plotting it via periodic calls from the bluetooth background method update() to my static Plot.plotData() method.

The latest feedback I have received “It sounds like you’re looking for an in-memory way to share data, and that’s simply not the way the Android activity model works.” In-memory???But this is rediculous. An Android phone has a limited amount of RAM for running Activities (one at a time), threads, handlers, Services, AnycTasks, etc. And an SD card for persisting data.

One critical person basically said: “In order to share data from a bluetooth background thread to my Plot activity (Plot.plotData()) that I must use the SD card.” ??? This just sounds nuts, because I have it working using my static method Plot.plotData().

Frankly I don’t see anything wrong with my solution primarily because those who criticize it do not follow up with a definitive alternative.

If you find my solution deficient please speak up and provide a definitive solution.” Unless I use a new thread, handler, Service, AsyncTask, etc, everyone assumes my solution is not a good one. Why? Supposing the criticism is valid, PRECIOUSLY What should I do instead of what I am currently doing?

Answer 1

One more time: if you have background task running you should create Service. That’s how Android expects applications to behave. Otherwise your thread may be terminated at any time (assuming none of the Activities are active).

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From documentation:

A service is a component that runs in the background to perform long-running operations or to perform work for remote processes

This precisely describes your case.

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Also carefully read Processes and Threads, specifically Process Lifecycle section.

Basically your application falls into Background Process or Empty Process group most of the time. That’s why you need Service started in your application.