Question

I am developing an application which has around 8 Activities, and a class which is used to connect/receive data to/from an embedded Bluetooth chip. When I started, a Bluetooth object was initialized in my initial Activity, where there was a Handler which received messages from the Bluetooth object.

After poking around on the internet for a while, it seems like the best idea for me is to turn my class into an Application subclass. However, doing this removes the need for me to initialize an object in the MainMenu, which removes my ability to pass it the Handler used.

Does anyone know of a way to eliminate the need for a Handler, so that every time the Bluetooth Application changes it state or receives data, the current Activity can access it?

My main problem with this approach is that the Activity doesn’t know when the Bluetooth Application will be sending it messages, the Application waits and listens, and then notifies the Activity when it happens.

OR

Is it bad practice for me to write the Handler into the MainMenu, have it handle messages for ALL the different activities, and then pass the Handler from Activity to Activity?

Answer 1

I’m going to assume that you’re trying to achieve the following as it’s a little unclear from your question your ultimate aim (sorry!):

1. Your application has several activities but only one Activity receives the data from the bluetooth device.
2. The other activities in in your application require the data from the bluetooth device but are not receiving it directly from the bluetooth device. Currently you’re providing the data via the one activity mentioned above.
3. You want to NOT use a Handler to achieve this.

If my above assumptions are correct then you are going along the correct lines but you probably do not want to use a Handler.

You are quite correct in having one Activity handle all the interactions with the Bluetooth device. It simplifies things and provides a much better, cleaner way of handling the Bluetooth device. However you need to get the data from this one Activity to all the others and to achieve this you would probably want to use Broadcasts, BroadcastReceivers and Intents. See here for an overview.

However if you can you might want to take a look at using LocalBroadcastManager as this keeps any broadcasts within your own app’s space. Broadcasts are global and should be avoided if you do not need to pass the data outside of your own app due to security implications.

Finally, have you considered using Fragments for your other Activities? Another disadvantage with Broadcasts is there is extra overhead associated with them. If you’re keeping data within your app then you can create an interface to be implemented by each of your Fragments and your main activity just calls that interface on the Fragment that is currently selected.