Android Developer

Service is the base class for Android services that can be extended to create any service. A class that directly extends Service runs on the main thread so it will block the UI (if there is one) and should therefore either be used only for short tasks or should make use of other threads for longer tasks.

IntentService is a subclass of Service that handles asynchronous requests (expressed as “Intents”) on demand. Clients send requests through startService(Intent) calls. The service is started as needed, handles each Intent in turn using a worker thread, and stops itself when it runs out of work. Writing an IntentService can be quite simple; just extend the IntentService class and override the onHandleIntent(Intent intent) method where you can manage all incoming requests.

OnRestoreInstanceState() - When activity is recreated after it was previously destroyed, we can recover the saved state from the Bundle that the system passes to the activity. Both the onCreate() and onRestoreInstanceState() callback methods receive the same Bundle that contains the instance state information. But because the onCreate() method is called whether the system is creating a new instance of your activity or recreating a previous one, you must check whether the state Bundle is null before you attempt to read it. If it is null, then the system is creating a new instance of the activity, instead of restoring a previous one that was destroyed.

onSaveInstanceState() - is a method used to store data before pausing the activity.

onTrimMemory(): Called when the operating system has determined that it is a good time for a process to trim unneeded memory from its process. This will happen for example when it goes in the background and there is not enough memory to keep as many background processes running as desired.

Android can reclaim memory for from your app in several ways or kill your app entirely if necessary to free up memory for critical tasks. To help balance the system memory and avoid the system’s need to kill your app process, you can implement the ComponentCallbacks2 interface in your Activity classes. The provided onTrimMemory() callback method allows your app to listen for memory related events when your app is in either the foreground or the background, and then release objects in response to app lifecycle or system events that indicate the system needs to reclaim memory.

Sticky Intents allows communication between a function and a service. sendStickyBroadcast() performs a sendBroadcast(Intent) known as sticky, i.e. the Intent you are sending stays around after the broadcast is complete, so that others can quickly retrieve that data through the return value of registerReceiver(BroadcastReceiver, IntentFilter). For example, if you take an intent for ACTION_BATTERY_CHANGED to get battery change events: When you call registerReceiver() for that action — even with a null BroadcastReceiver — you get the Intent that was last Broadcast for that action. Hence, you can use this to find the state of the battery without necessarily registering for all future state changes in the battery.

Job Scheduling api, as the name suggests, allows to schedule jobs while letting the system optimize based on memory, power, and connectivity conditions. The JobScheduler supports batch scheduling of jobs. The Android system can combine jobs so that battery consumption is reduced. JobManager makes handling uploads easier as it handles automatically the unreliability of the network. It also survives application restarts. Some scenarios:

☛ Tasks that should be done once the device is connect to a power supply

☛ Tasks that require network access or a Wi-Fi connection.

☛ Task that are not critical or user facing

☛ Tasks that should be running on a regular basis as batch where the timing is not critical

☛ You can click on this link to learn more about Job Schedulers.