1. Plan for today Open-Closed and Quizmaster
Review of open-closed principle
Hopes, dreams, aspirations, reality
What is refactoring for?
Design first, code second? Repeat until done
Third-party APIs v Stock Android
How to navigate the online space of options

2. Quizmaster Review and Preview
Where are quizzes found?
Hard-wired/coded in QuizGenerator.java
Stored in XML files as part of assets, read and parsed by custom XMLxyz.java classes
What's missing here? Web-based quizzes
How could these alternatives co-exist?
Design for complete/some flexibility, then implement
Get quiz from web, then increase flexibility

3. Toward Internet/Web connections
Services and permissions on Android must be dealt with intentionally
To open a connection to Internet? Must supply app permission
Permission levels for Android Applications
Android 6.0 change in model
Runtime permission vs. Install permission
We'll see more on best practices later

4. Adding Permissions for Applications
Use AndroidManifest.xml for permissions
Open Internet socket/connection --- aside: what is a socket?
Also access network state (not needed here)
<uses-permission android:name=
"android.permission.INTERNET" />
<uses-permission android:name=
"android.permission.ACCESS_NETWORK_STATE" />

5. How to access Internet? Step one: Google, StackOverflow, Android book
Open HTTPConnection, similar to how this is done in Java
See code in JSONQuizGenerator.java and method getJSONRaw()
Examine code in gitlab:

6. Concepts in this version of code
Create URL (see constructor), what is a URL?
Store URL as instance variable for use in method to make connection
Alternative from Java/design perspective?
What to do with Exceptions?
In general, throwing exceptions to top level is a good idea
What is alternative?
What about application specific exceptions?

7. Concepts in HttpURLConnection
Create the connection
Options required or available: type of connection, duration of "try and try again"
Get response code for connection, verify
Open stream for connection
Read stream for connection
Notice stream reading code
Decorator design pattern (more later). Create readers from streams and readers from readers
Dissect code in .readStream()

8. How to test the connection?
Deploy to phone, offer user choice of creating quiz from online/Internet
Get ready to debug
Android.os.NetworkOnMainThreadException
Say what?
E/InputEventReceiver: Exception dispatching input event.
:46: /edu.duke.compsci290.quizmaster E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
:46: /edu.duke.compsci290.quizmaster E/MessageQueue-JNI: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1303)
at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:86)
at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:74)

9. Is Google/Search your friend?
AsyncTask enables proper and easy use of the UI thread. This class allows you to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.
Who will be happy with this approach?

10. Third Party APIs You will often see these on StackOverflow
How do you know which are "good"?
Good judgment comes from experience, experience comes from bad judgment
Good design comes from experience, experience comes from bad design
Side note: attributing quotes is problematic
In our case if it's referenced in Android documentation …

11. Let's use the Volley library/APIs
Volley is an HTTP library that makes networking for Android apps easier and most importantly, faster. 
How to add GitHub or other library to project?
Differences: Android Studio and other Java projects – managing dependencies
Maven, Gradle, others
Trust or investigate fully or …

12. Let's use the Volley library/API
Choose the right Build.gradle file
compile 'com.android.volley:volley:1.0.0'
Magic happens (ok, that's relative)

13. What does Volley get us?
Handle network requests simply and appropriately on the right non-UI thread
Call back to main UI thread you manage
See code in new getJSON() method
StringRequest request =
new StringRequest(Request.Method.GET,mURLString, new Response.Listener<String>(){ // override method here }, new Response.ErrorListener(){ // override method here });

14. What is JSON and why not XML?
Given that we have XMLQuizParser what might be appropriate for testing Internet?
Copy XML file to Internet, get it, parse it, …
Why use JSON instead?
JavaScript Object Notation
What does Google say it is?
Why is it popular on the web?
Why is it used in Android applications?

15. JSON Example http://www.cs.duke.edu/csed/quizzes/oscars.json
What is format for JSON file?
This example is NOT created to play nicely with our Quiz and Question classes
However, Compare JSONParser class to XMLQuizParser class
Better alternative: Gson library
Parse directly to Java class/object: reflection