7.3 Broadcasts & BroadcastReceivers

Question 1

Broadcast Definition

Answer 1

Messaging components used for communicating when an event of interest occurs

Question 2

BroadcastReceiver Definition

Answer 2

The components in you app that listen for app or system events and respond accordingly

Question 3

What are the different types of broadcasts

Answer 3

1. System broadcasts: delivered by the system

2. Custom broadcasts: delivered by your app

Question 4

How do system broadcasts work?

Answer 4

These broadcasts are wrapped in an Intent object:
- The intent object’s action field
contains event details
-(e.g. android.intent.action.HEADSET_PLUG)

• Intents can also contain more data
  about the event in the extra field
  -(e.g.as a boolean for whether or not the
  headset is connected or disconnected )

Question 5

What must an application do to receive a system broadcast?

Answer 5

Interested apps must register a component to “listen” for these events via a BroadcastReceiver

Question 6

When do you use custom broadcasts?

Answer 6

When you want your ap to take action without launching an activity.

For example, to let other apps know that data has been downloaded and it’s available for those apps.

Question 7

What are the different types of custom broadcasts?

Answer 7

1. Normal broadcasts
2. Ordered broadcasts
3. Local broadcasts

Question 8

What are the methods associated with the different types of custom broadcasts?

Answer 8

1. Normal broadcasts:
   sendBroadcast( )
2. Ordered broadcasts:
   sendOrderedBroadcast( )
3. Local broadcasts:
   LocalBroadcastManager.sendBroadcast( )

Question 9

What makes normal broadcasts different from the other types?

Answer 9

It sends broadcasts to all registered receivers simultaneously, in an undefined order.

They can’t propagate (spread) the results among themselves

They cannot cancel the broadcast

Question 10

An example of a normal broadcast

Answer 10

public void sendBroadcast() {
Intent intent = new Intent();
intent.setAction("com.example.myproject.ACTION_SHOW_TOAST");
   // Set the optional additional information in extra field.
intent.putExtra("data","This is a normal broadcast");
sendBroadcast(intent);
}