Data Storage

Question 1

What are the 6 data storage options on android? Define each…

Answer 1

Shared Preference -> Structure that contains key-value pairs of primitive types.
Internal Storage -> Small, on device storage.
External Storage -> External storage for larger memory.
SQLite -> Lightweight relational database.
Files -> Store data on files.
Cloud -> E.g Google Cloud or Azure.

Question 2

What is the purpose of Cache Files? How do we get the cache directory?

Answer 2

Store temporary, non-persistent files.
Obtain through the getCacheDir( ) method.

Question 3

What library is Shared Preferences in?

Answer 3

Android.content.SharedPreference

Question 4

What are the 3 things Shared Preference are mainly used to store?

Answer 4

State information
Preferences
Shared Data

Question 5

What type of file is Shared Preferences stored in?

Answer 5

XML

Question 6

What is the difference between Shared Preference and Saved Instance State.

Answer 6

Shared Preference -> Saves data across sessions, persistent data, stores user preferences.
savedInstanceState -> Focuses on reconstruction of the UI after rotation.
Both store small and private data.

Question 7

What are the 3 levels of Preferences?

Answer 7

Activity.getPresferences( ) -> Activity wide.
Activity.getSharedPreferences( ) -> Application wide.
PreferenceManager.getDefaultySharedPreferences( ) -> System wide.

Question 8

What is the purpose of a preference fragment?

Answer 8

Creates a hierarchy of preference objects.

Question 9

Give a brief definition of what a Shared Preference is…

Answer 9

A Shared Preference is a bundle of key-value pairs that store persistent app data.

Question 10

What are the 5 main uses of Shared Preference?

Answer 10

Login information -> E.g email, password, username.
User Actions -> E.g Store previous queries.
Cache data -> Improves app efficiency.
Persisting Application State -> E.g if something has been completed by the user.
User Preferences -> E.g font size, theme.

Question 11

When and why is getSharedPreferences( ) called? Explain it’s parameters…

Answer 11

To create the initial SharedPreference instance, or return the existing one.
Argument 1 -> The name of the SharedPreference.
Argument 2 -> The mode of the Shared Preference. This determines the preferences accessibility from other apps.

Question 12

What are the 5 steps for using Shared Preferences?

Answer 12

1) Get the SharedPreference instance.
2) Get the editor for the SharedPreference instance.
3) Put values into the preference (primitive types).
4) Commit the changes to the preference instance.
5) Get values from the Shared Preference.

Question 13

When getting values from the SharedPreference, what are the arguments of the Get method?

Answer 13

Argument 1 -> Key value
Argument 2 -> Default value if the key is not found.

Question 14

What is a Preference Fragment?

Answer 14

A UI component that displays a heirarchy of preferences that the user can interact with.

Question 15

When is a Preference Fragment mainly used?

Answer 15

In an Activity in which the user can interact with the UI to change persistent attributes of the app. For example, a Settings activity, in which user changes are saved to the Shared Preference.

Question 16

Where does a Preference Fragment save to?

Answer 16

Shared Preferences.

Question 17

What class does a Preference Fragment extend?

Answer 17

Fragment.

Question 18

What are the 3 steps to implementing a Preference Fragment?

Answer 18

1) Create a class that extends PreferenceFragment.
2) Define an XML for the Preference Fragment.
3) Inflate the XML and add to the activity.