2: Android

Question 1

descrbibe the the android OS

Answer 1

runs a variant on linux which has been stripped down for mobile devices with a Java VM on top. it has one user, one host

Question 2

define discovery and wiring in the context of Android

Answer 2

discovery: what app offers what service
wiring: choosing which component will do the service

Question 3

what are the four component types in android?

Answer 3

activity
service
content providers
broadcast receivers

Question 4

what is an activity?

Answer 4

an activity corresponds to one screen
e.g mail app might have:
compose, inbox, outbox...
all diff activities
apps move between activities, passing data between them

Question 5

how do components communicate in android?

Answer 5

the calling component uses an Intent to announce the wish for communication
the called component has an intent filter to receive the Intent which must match the conditions of the filter
note an intent is not for an app, it is for an activity. an app is just a set of components linked by intents

Question 6

how do we deal with these issues?

No provider for an intent
Many possible providers
Component crashes

Answer 6

● No provider for an intent
● Don’t offer the option to the user

● Many possible providers
● Ask the user to choose

● Component crashes
● Revert to the calling activity? Fail? Home screen?

● The point is that there is a single user who can
be regarded as being in control