Lecture 7 (06-23)

android yayayay

”A collection of screens”

todo ask if we can use kotlin (for funzies — we are quite familiar with java yknow!? More of a challenge!?)

Activities

• A big flow chart
• onStart = screen is visible but you CANNOT interact with it yet
  • A “transient state”
• onResume = you can actually interact with the screen
• onPause = screen is visible but not interactable (again…?)

The id of elements should be unique (in order to refer to them in the code)

Bundle is your previous “state”.

• To know what state you had before
• If you’re starting from scratch every time, it’s prolly useless

setContentView renders a certain layout.

All items in XML are a subclass of View

• Buttons, EditText, etc.

View groups are also views. Views in views!

Activity!

android.intent.action.MAIN specifies this is the “main” activity

idrk what hes talking abt

We only doing unit testing. Ignore testing android UI stuff in the video provided

colors.xml has your palette colours (instead of hard-coding them!)

Gradle

• Automates building your app
• compileSdk 31 — That is the thingy you’re actually compiling
• targetSdk 31 — Thingy you are “targeting” (should be less than or equal)
• minSdk 21— The lowest that works (the more devices you can support)

Storing things persistently

• File System (FileWriter, json specifically)
  • Unorganized; not that much; small
• For organized data, Shared Preferences or Db is prolly better
  • Shared preferences = as a XML file
  • SQLite or Firebase
    • SQL for excel-like stuff
    • Firebase Realtime Database
      • This is what we are using for our project!
      • DB is stored online (you can interact w/ it and whatnot)
      • Any changes to the Db will be communicated to everyone monitoring the Db
        • I.e. when making an announcement, everyone gets notified
• Firebase uses JSON
  • Everything is stored as a key-value pair

onClickAdd

• Passes the View that it was called by
• R is a file (id is a static field of the class)
  • findViewById takes an ID and u find it like that mhmhm

Multithreading

• setOutputText is the “old main thread” and instancing new ValueEventListener creates a new thread ? So whatever variables exist outside the function is copied and yeah yeah.
• Basically u needa make sure the new thread returns the changes such that the old thread is correctly updated, instead of updating values as if it updates the old thread, which it doesnt.