What is the difference between a Listener and a Receiver (Android)?

Question

For instance, I need a BroadcastReceiver to get these events:

REBOOT or SHUTDOWN

SCREEN ON or OFF

battery status (voltage, plugged in, temperature)

physical button presses (camera, media, etc.)

But I need Listener to get these events:

EventListener for sensor events (acceleration,magnetic fields, orientation, proximity, temperature, light level, etc.)

LocationListener for location events (Network location, GPS)

It seems like both Receivers and Listeners both exist so that I can receive events. Other than the obvious semantic differences, what are the difference between the two? Are there things I can do in one but not the other, especially in regards to things like how much CPU I can take and running while the screen is off? Why are there two totally different constructs for the purposes of receiving events?

Answer 1

There are so many differences between these two, them responding to something is one of the only similarities.

Differences:

• BroadcastReceivers receive Intents whereas a Listener can do basically anything, since it does not have a defined purpose, it's just a naming convention. Eg, search for "BroadcastReceiver" on the dev website then search for "Listener"

• BroadcastReceivers just receive an Intent Broadcast which is non-direct, Listeners get called explicitly.

• A BroadcastReceiver is its own defined class since it has a definite purpose (receiving Intents) whereas Listeners can be anything - they're usually an interface and they are provided so that callbacks can be made from one class to another.

• BroadcastReceivers are usually used for global, system-wide events, Listeners for specific events (ie a Location sensor shouldn't give location updates every second unless it has something, such as a Listener to publish to. Contrasted with a screen-off intent - this is important, it affects everything, and so should be broadcast to all interested Receivers)

• Events a BroadcastReceiver picks up are usually non-continuous events (one shot), whereas Listeners, depending on what they do, can be used for constant updates (continuous).

• BroadcastReceivers can be instantiated by the system if they're declared in the manifest, Listeners are only dynamically made (so via code).

• CPU/Power usage depends on implementation of both, especially since as mentioned, Listeners can be anything.

Are there things I can do in one but not the other, especially in regards to things like how much CPU I can take and running while the screen is off?

BroadcastReceivers only have 10 seconds of guaranteed execution time. Listeners, since they don't serve a specific purpose, don't have this limit.

What you definitely can't do from a BroadcastReceiver:

In particular, you may not show a dialog or bind to a service from within a BroadcastReceiver.

There are probably more - this is what I came up with.