how to structure my app to run in background

I开发者_C百科 am new to Android, and I need some advices for start up.

I want to build an application, which will show up, when the user gets into some hot situation.

By hot situation I mean:

• the GPS/cell coordinates are in known zone;
• known Bluetooth device detected;
• known Wi-Fi network detected;
• weather info has change;

I see something running in background and when one of the clauses hit, it will trigger and open the app.

• How to get started?
• How do I make sure my app won't be shut down?

As I read somewhere that Android OS will terminate apps if memory out occurs or consumes too much, and my app would consume a lot, making repeated measures/checks to see if situation changed.

Regards,

Pentium10

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You need to use a Service for the part of your application that runs in the background.

You might find the Application Fundamentals document in the Android Developer Documentation helpful. It says this about Services:

A service doesn't have a visual user interface, but rather runs in the background for an indefinite period of time. For example, a service might play background music as the user attends to other matters, or it might fetch data over the network or calculate something and provide the result to activities that need it.

In you case you might find the LocationManager Service helpful. It is a system Service which will you can use to notify your application based on GPS position.

However, I think you'll have to write your own Services to monitor Wi-fi, Bluetooth and weather.

You can use the AlarmManager Service to get your Service to perform particular tasks at certain intervals.

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It depends on how & where you want to deploy your application. In my experience it boils down to

1. you create an application for a specific use case where battery drain matters less than accurate results (showcase situations, prototyping, ...)
2. you want to distribute the application to users.

In case 1) just create one service that aggressively polls the sensors / web services. Use the AlarmManager to send a REFRESH intent (AlarmService.setRepeating(...) ).

That REFRESH intent will restart the synchronization service everytime, even if it was killed by the system. onStart() will be called everytime the REFRESH intent is emitted. You can do heavyweight setup logic in onCreate() as this will be called everytime the service is created after it was destroyed. WARNING: This will possibly drain the battery very quickly.

In case 2) I would create several services and let the user configure different polling intervals for each service to limit battery drain. I can see for example that bluetooth should be polled more regulary than GPS as it is more likely that a bluetooth device suddenly appears than a user moving extremely fast.

Weather sounds extremely expensive (network lookup, possibly triggering a network connection!)

Please do not try to be too persistent with your app in case 2). It usually makes a lot of sense for a phone to kill memory / power draining services.