TravelTimeCalculator: Selecting Coordinates to Scan for Directions

I'll simplify the selection of destination coordinate to scan for. Instead of having the app selecting some coordinates around the center, I'll let the user select the coordinates by tapping on the map.

The work flow will be like:

• User re-zooms and pans the map to a new origin:
• Clear existing markers (clearMarkers)
• The app searches for any existing directions starting or ending at the coordinates (getDirectionsFromDb)
• If found, it adds corresponding markers (addMarkers).
• If the user taps the map,
• If coordinates are not found in database, (getDirectionsFromDb is null)
• Send Google Directions requests, (getDirectionsFromUrl)
• Save response to database (saveDirectionsToDb)
• Add marker to map
• If coordinates are found, add marker to map

Step 1: Add a OnMapClickListener
I followed the instructions regarding detecting a tap on map from the official documentation. As soon as the map was installed, it crashed. The crash was my mistake, since I added the code in "onCreate". After adding the code to "onMapReady", it worked.

Step 2: Create a new class, TravelTimeHandler that handles the requests and decides whether to send a Directions query or query the database. It shall also add data to the database.

I moved the methods getDirections and readDirections to that class.

Step 3: Define what methods new methods to use.

• readDirectionsFromJson
• getDirectionsFromUrl
• getDirectionsFromDb
• saveDirectionsToDb
• clearMarkers
• drawMarker

Step 4: Implement those methods.
I'll cover this step in the next blog post