I am creating a project which connects to an embedded Bluetooth chip. Currently I have it set up with a separate application class which controls all the bluetooth functionality.
My program initialized with a main menu that has 9 buttons. In the main screen I create the connection to the Bluetooth device. Each button brings me to a separate Activity. Each activity needs to receive different pieces of data from the Bluetooth chip.
My question to you all is, would it make sense for me to use a service instead of an application? From what I understand of a service, it is used because there is always something running in the background. However in this case nothing needs to be running in the background ( unless keeping the connection with the Bluetooth device counts), data is only sent/received when an Activity asks for it.
Or, am I completely off track and shouldn't use either? Just a simple class to act as my data container which can be passed through intents? I know this will work, but am very new to Android and intents seem to be a bit messy. I would rather not use intents if I didn't have to.
I'm also building up a bluetooth connection, and i put the whole communication stuff in a service and bind to this service with every activity that needs to use the connection. This works pretty well for me. You might want to choose this way too.
Actually i earlier realised a way holding the connection in the application, but now i prefer the service way, because i'm using the application for global states.
Using service also reduces the need of intents to a very small amount :)
In your case a static property for the bluetooth connection would be the most pragmatic solution
Related
When I started working on a mobile application using Android SDK, I wanted to make a BluetoothService class, which would allow me to connect to a paired device and communicate with it by injecting the service whenever I need to.
However, when I tried to implement the Service, I realised that Android BluetoothAdapter depends on an Activity (aka. an active view). So I gave up the idea of having a Service and implemented the Bluetooth directly in the view.
Although it worked, I still had a problem.
Basically, my application was a remote that could be used to control a specific joint/stepper motor of an articulated arm at a time.
Whenever the user wanted to switch to another joint, they either could use the upper right menu, or press the picture at the top (depicting a picture of the arm) to get to another view, where they could press on the part they wanted to control (directly on the picture). It would then return them to the main activity with the arrow buttons.
However, the fact that the application is switching to another activity means that the previous one was destroyed. As such, it happened that the application would temporarily lose the Bluetooth connection with the other device, whereas using an injectable BluetoothService would have allowed my application to carry it over different activities.
Why do I need an Activity to use BluetoothAdapter?
Permissions and discovery require an activity because they require user input. The rest of the Bluetooth APIs should, on the whole, not require an activity. In particular, once you get a BluetoothDevice, the actual Bluetooth I/O should be able to be done without an activity.
In your case, it is not clear that you really need to be doing this work in the background, so a service may not be required. Either:
Use a single activity for all of this work, using fragments or something to handle the work being triggered by the action bar item; or
Have the Bluetooth communications be managed by some singleton, perhaps using a variant on the repository pattern, that lives outside of either activity
I am developing an android app with BLE API from android. My app needs to connect to a BLE device, and remain connected as long as it is in range and turned on. I need to read data from it, and write data to it.
I am trying to follow the MVP architecture pattern, not strictly since activities are the starting point. But anyway, I wanted to know where should I put the interaction with Bluetooth? I am searching for answers for the following questions. I have searched StackOverflow, but couldn't find what I was looking for.
Should it be in a service bounded to the UI just like in googlesample ble app ? But, I think that would break the whole mvp architecture.
Should it be a bounded service at all ? If no, what would be the best way to implement the service? In my mind, if it's not bounded to the view, and there is a callback from the background service to display something on the UI, there is a possibility of undefined behavior.
Who should initiate the Bluetooth interaction ? The application class or some activity ?
I am looking for mainly architectural guidance, and best way to go about developing this app.
Since you have the requirement that the Bluetooth connection should keep working in the background, you should have a Foreground Service somewhere running in your app process. This will make sure your app process will be kept alive, but requires an icon to be displayed in the phone/tablet's top bar.
Whether you actually put your BLE code in this service class or not doesn't matter for the functionality.
There are of course many ways to achieve good architecture but here is my approach.
My approach would be to have a singleton class that handles all your BLE scanning, connections and GATT interactions (from now on called Manager). Since some BLE operations needs an Android Context, a good way is to use the Application context as context. Either follow Static way to get 'Context' on Android? to be able to fetch that context at any time or subclass the Application class and from its onCreate call some initialization method in your Manager and pass the context. Now you can keep all BLE functionality completely separated from Android Service/Activity/Application stuff. I don't really see the point in using bounded services etc. as long as you keep everything in the same process.
To implement a scan functionality, you can have a method in your Manager that creates Scanner objects. Write the Scanner class as a wrapper to Android's BLE scanner and expose methods to start/stop scan. When you create a Scanner that method should also take an interface as argument used for callbacks (device reports and errors). This class can now be used in for example an Activity. Just make sure that the scanner gets stopped in the Activity's onStop method to avoid leakage of objects.
There are several reasons for having a wrapped custom Scanner object instead of using Android's BLE scan API directly in the Activity. First you can apply the appropriate filtering and processing of advertising packets so it handles your type of peripheral and can show high level parameters (decoded from advertising data) in your custom advertising report callback. The manager should also listen to broadcasts when Bluetooth gets started/stopped/restarted and keep track of all started Scanners so the Scanners are restarted seamlessly when Bluetooth restarts (if you want this functionality). You may also want to keep track of timestamps of all scan starts/stops so you can workaround the new restrictions in Nougat that limits it to 5 scans per 30 seconds.
Use a similar approach when you want to connect to your peripherals. You can for example let the Manager create Device objects which have methods to start/stop the connection and have a callback interface to report events. For each supported feature (for example read some remote value) you should expose a method which starts the requests and have a callback which is called when the result arrives. Then your Manager and Device class takes care of the GATT stuff (including enqueuing all your GATT requests so you only have one outstanding GATT operation at a time). Just make sure you can always abort or ignore the result when you don't want the result, for example if an Activity's onStop or onDestroy method is called.
Since you probably want to reconnect automatically in case the device gets disconnected, you should use the autoConnect flag and set it to true when establishing the connection, which assures this. Again, the Manager should keep track of all active Device objects and automatically recreate the BluetoothGatt object when Bluetooth is restarted.
To be able to display different kind of UI stuff, like for example automatically show a warning message in your Activity when Bluetooth is turned off and remove it when Bluetooth is turned on, you should be able to register Listeners to your Manager. Have a method in your Manager for registering/unregistering a listener (which is really just a Callback) object, keep track of all the listeners and when Bluetooth state change happens, call all listeners. Then in your Activity's onStart you register a listener and in onStop you unregister it. You can have a similar approach for your Device's BLE notifications, where applicable.
What's left is how you deal with different Threads. As you might know most BLE callbacks from Android's API happen on Binder threads, so you may not update the UI from them. If you otherwise in your app don't use anything other than the main thread, you can for example post all invocations of callbacks in the Manager to the main thread, or maybe move to the main thread directly when the callback from Android's BLE stack arrives (but then be aware of things like https://bugs.chromium.org/p/chromium/issues/detail?id=647673). Just make sure you never touch the same variables from different threads.
Also if you target API 23 or higher you need UI code to let the user give permission to Location to be able to start scan. I suggest you implement this in your UI code and not in the Manager, or implement some "wrapper" or helper method in the Manager to do this.
RxCentralBle provides a paradigm for use in an app. The library design clearly shows the structure of the library. In short, RxCentralBle provides reactive interfaces for the primary Bluetooth LE actions:
BluetoothDetector - detect phone Bluetooth State
Scanner - scan for peripherals
ConnectionManager - connect to a peripheral
PeripheralManager - queue operations to communicate with a peripheral
It's recommended to subscribe to these interfaces on a background thread and ensure resources and subscriptions live at the application scope i.e. member variables of your Application class. As long as your Application is running, all Bluetooth LE resources will remain alive and active.
Check out RxCentralBle's Wiki and sample app to learn more.
i am creating an app in which from many activity we send and receive data through Bluetooth ,
so if i release socket in 1 activity ,so in other activity i have to connect that socket again
,so some time it is connect and sometime it disconnect , so how can i create only 1 socket and share to all over app?i have already tried to make 1 conman class to share but that also did't worked out.
the right way to maintain Bluetooth connection between different activities, and in general - to share any Object across the entire application, is by using a Service class.
android Service derived class is the facility for your app to perform operations, and hold references to objects that needs to maintain it state regardless if any Activity changed, or even when there is no any Activity at all (when your app is in background)
you can bind the current foreground activity to a Service, and by that - to communicate with it from the current activity.
for more info - read: http://developer.android.com/guide/components/services.html
you'll find tones of tutorials and samples by searching on android Service, and binding to a Service...
I guess that for someone who not familiar with android Service - it would look a little complex and hard to understand ant implement, but eventually it's one of the most important component of the API's, so it worth the effort.
I'm working on an Android application interacting with Arduino. I'm trying to manage multiple activities, each one being responsible for controlling a specific part of the Arduino board.
Unfortunately, tutorials on the web use only one activity. So I don't know how to proceed for keeping the connection with Arduino alive while navigating to a new Activity or for closing it properly and then re-open it on the new Activity.
Any idea?
You could use a Service to connect to Arduino and to keep that connection open. Your Activities can then talk to the Service, being started, stopped, switched, etc.
EDIT: How this can be done is already handled by another question/answer:
Long running ADK Accessory (Service?)
I haven't used Arduino with Java before, but you might want to follow a Singleton pattern. Using a Singleton pattern, whatever objects you are using to connect to it can be accessed from multiple activities and multiple threads.
Using a Singleton will only alleviate your problem though. You still need to figure out how to close/reopen it.
Also, it is important you know how the Activity Lifecycle works. If a user receives a phone call, the screen turns off, or the orientation of the screen changes it will destroy your activity and recreate it. You'll have to handle how you're going to save and restore where you were. This will most likely mean you have to close/reopen the connection.
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?
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!):
Your application has several activities but only one Activity receives the data from the bluetooth device.
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.
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.
You can use BroadcastReceiver class to send broadcast messages to your activities. see here http://developer.android.com/reference/android/content/BroadcastReceiver.html
When you get the data you need into the application class, you can send it to the activity you want.. just make sure that the activity has registered to receive that broadcast message..