Instructions:

Start with the "basic activity" template in Android Studio.
Add Firebase support as demonstrated in the following Section Video.

a) Startup: A drawing space (SurfaceView canvas) above a FAB for Clearing the content in the lower right, and two more FABs on the left for undo and redo of strokes.	b) Drawing with multiple fingers paints with different colors (from a pre-set color palette)

c) When changing device orientation to Landscape, the activity adapts the view as best as possible (but no scrolling required)	d) New (multi-)touch events still paint onto the View

e) Back in Portrait mode, all strokes are still painted, but some may have moved off the screen.

All strokes (segments drawn between finger down and finger up events) should be stored in your Firebase, so when you leave the app and start it up again, the last drawing is still available, and undoing strokes should still work based on how you originally drew your sketch.

Please use the same naming conventions for package and app as in the previous homeworks, i.e., name your app <FirstInitialLastname>MultitouchFire.

Implementation Hints:

(Re-)Read "Canvas and Drawables". We suggest the use of a SurfaceView in the following way:

• Create a new class that extends SurfaceView and implements SurfaceHolder.Callback
• Create a constructor with the right signature and don't forget to call super.
• At the end of the constructor, add the instance as a callback to the holder

• We recommend that you get drawing implemented first, and then worry about capturing strokes, and then about storing strokes in the Firebase. Don't worry about all these things together - sequence them into steps.
  
  
• Override onTouchEvent(MotionEvent event) and return true at the end. This is where you will handle all (multi-) touch events
  
  
• Create a private function to refresh the view (should get called whenever you want to make sure that drawing updates get flushed out (e.g. in the surfaceChanged callback function, in your clear function, and in your onTouchEvent(MotionEvent event))
  
  
• Set up your main Activity's layout to contain your new class (you can go into XML and create a new tag with your class's fully qualified name e.g. edu.ucsb.cs.cs184.uname.<your_class>) and three Floating Action Buttons. Set up your main Activity to listen to the Buttons' click events and forward them to your class instance (you can retrieve your class instance the same way as any other view with findViewById).
  
  
• Pre-set color palette: Use a Typed Array of color values, that you define in res/values/colors.xml to use as paint for the finger strokes. Different fingers in a multi-touch event should have different colors. Subsequent single-finger strokes should be of different color. Here is the set of (chosen to be harmonic) colors we used for the above screenshots: #1abc9c, #2ecc71, #3498db, #9b59b6, #34495e
  
  

Extra Credit:

For an extra 4% of the points, implement support for multiple users contributing to a drawing in parallel. Start with Android App User Sign-In UI via Firebase, and log the user id with any stroke drawn. Then, make sure that whenever a stroke is added to the database, it is reflected in any of the clients (2 or more) that are currently connected to the Firebase. Also, undo, redo, and clear should only operate on a user's own strokes - other users' strokes should stay unaffected.

This may sound more difficult than it actually is, since that is the kind of thing that the Firebase Real-Time database excels at and was built for.

Additional small requirements for allowing simple testing by the TAs: Your login screen needs to support Google account login, as the TAs will test this functionality by logging in with multiple Google accounts. This is supported by the Firebase Android User Sign-In UI, so it should not be an extra effort. Just making sure that you support that option!

Hand in:

• Complete program code to solve this assignment. You don't need to submit the image files. As always, add a README.txt file briefly acknowledging outside sources and any input to the grading TAs that you deem useful, such as, for example describing your approach, any roadblocks you encountered, and if you tackled any extra credit.
   

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