Tutorial: Maps

DUE Wed, 10/8, 2 pm

This tutorial may be completed individually or in teams of at most 2. You can partner differently for each tutorial.

In this tutorial, we’ll add map and location info to Chatter.

Due to location privacy concerns, mada.eecs.umich.edu will not be available for this tutorial. Continue to treat your messages sent to chatterd and Ollama as public utterances with no reasonable expectation of privacy and know that these are recorded and shared with everyone using chatterd.

Objectives

• Work with on-device streaming data: AsyncStream in Swift, Flow in Kotlin
• Use the location manager
• Access the magnetometer and accelerometer
• Work with Apple MapKit SDK or Google Maps API
• Implement multi-screen navigation
• Implement swipe gesture to transition between screens

APIs and protocol handshakes

To support posting and retrieving geodata information, we add two APIs to Chatter. These are simply modified postchatt and getchatts APIs that accommodate geodata:

• postmaps: uses HTTP POST to post a chatt with optional geodata info as a JSON object, as described below.
• getmaps: uses HTTP GET to query the database and return all posted chatts, with optional geodata, again, as described below.

Using this syntax:

url-endpoint
-> request: data sent to Server
<- response: data sent to Client

The protocol handshakes consist of:

/postmaps
-> HTTP POST { username, message, optional geodata }
<- {} 200 OK

/getmaps
-> HTTP GET {}
<- [ array of chatts with optional geodata ] 200 OK

Modified Chatter API data formats

We define a user’s geodata to comprise of their geolocation and velocity (facing and speed) at the time of posting a chatt.

As in previous tutorials, the chatts retrieval API sends back all posted chatts in the form of a JSON Array of string arrays. In addition to “username”, “message”, “id”, and “timestamp” of the Chatter tutorial, each string array now carries an additional element which is itself an array of the user’s geodata (in order): latitude (lat), longitue (lon), location (corresponding to the lat/lon), compass point facing, and speed. If a chatt has no geodata, this element must have value JSON NULL.

[
  ["username0", "message0", "id0", "timestamp0", "[lat0, lon0, \"loc0\", \"facing0\", \"speed0\"]"],
  ["username1", "message1", "id1", "timestamp1", "[lat1, lon1, \"loc1\", \"facing1\", \"speed1\"]"], 
  ... 
]

To post a chatt, the client correspondingly sends a JSON object with keys “username”, “message”, and “geodata”, where the value for key “geodata” conforms to the format above. For example:

{	
   "username": "YOUR_UNIQNAME",	
   "message": "Hello world!",	
   "geodata": "[42.29, -83.72, \"Ann Arbor\", \"South\", \"walking\"]"
}

Notice that both the “facing” and “speed” elements are descriptive, as we’ll explain later.

Specifications

You must first upgrade one of the alternative back-end servers.

• Maps Backend

then one of the front ends:

• Maps Compose
• Maps SwiftUI