Android overview

Question 1

Android vs Apple

Answer 1

• open source
• can run on many devices
• easy to inspect reverse and modify Android apps
• side load permits to test developed apps
• easy to jailbreak.
• can be customized by vendors (Open source, problem of security patches)
  • widespread, more interesting for research purposes
• security problems

Question 2

Languages used to write android apps

Answer 2

1- Java
2- Kotlin
3- c/c++ (useful for low level task)

Question 3

Android APIs are used for?

Answer 3

• for apps to interact with the “external world” (via the API)
• for the Android framework to interact with the Android app
• > Many java API are part of Android APIs

Question 4

Can android apps be executed in non-android devices?

Answer 4

No, they can only be executed in the Android framework (phisical device or emulator).

Question 5

Android general architecture (from lower to higher)

Answer 5

1- Linux Kernel
2- Hardware Abstraction Layer (HAL) to interact with hardware and sensors
3- Android Runtime (supports android apps runtime execution) + Native C/C++ libraries
4- Java API Framework
5- System Apps (pre-installed)

Question 6

Android framework APIs

Answer 6

• many, differ from features but not base framework
• old APIs are deprecated but not removed
• backward compatible
• identifyed by integer

Question 7

package name

Answer 7

• each app has a package name “com.company.app”
• unique identifier
• two apps cannot have the same package name (both android and playstore)

Question 8

Four main components types

Answer 8

• Activity
• Service
• Broadcast Receiver
• Content Provider

Question 9

Activity

Answer 9

• entry point
• has an UI
• app could have many, but one must be chosen as launcher
• external apps can interact with activity
• other activities in same app can interact with activity
• has a lifecycle

Question 10

Service

Answer 10

• no UI
• generally executed in background (in some cases foreground)
• cannot be launched with graphical launcher

Question 11

Content providers

Answer 11

• databases
• used to share data between apps
• app can query and interact with data

Question 12

Intents

Answer 12

• applications can communicate with each other through intents
• explicit (specifies components to communicate with)
• implicit (no target, only action type)
• broadcast intent

Question 13

Intent filter

Answer 13

• declaration in manifest

* necessary if anactivity can receive a certain intent

Question 14

Manifest file

Answer 14

• fingerprint of the app
• hall details and key informations
  
  • permissions
  • intent filters
• XML file

Question 15

Important Android tools

Answer 15

• Android Studio
• adb
• sdkmanager
• avdmanager
• compilation with gradlew from the terminal
• app-debug.apk