Module 12: Creating an Uber Clone
Transcript
next we’ll bind the websocket logic and map UI to bring this all together we can get started with a location service class similarly to the user service class that would abstract the local location unlock the user service class the location service class should also deal with the physical location of the device these are the same constants we have on the server when sending a location update to the server I don’t want to exceed a fixed amount of updates so we won’t burden the server or our Network the Clause has a private Constructor so the only way to create the location service is via the bind method which in turn invokes the instance method bind impul we provide two callbacks one is for a car being added which we will use to bind a new car to the UI and the other is for location updates so we can position the map location update notifies the server about changes to the location and also invokes the Callback once we can position the map we invoke the callback with the location so the map can be shifted to our current position once the server socket is connected we start sending location updates there we open the websocket connection using the connect call we cache the last set of values so we don’t send data to the server unless something changed easy threads lets us Post jobs onto a dedicated thread so we don’t have to block the main EDT it also means we don’t need to deal with synchronization or any other complexity related to that as all operations happen on that thread until on open is invoked the connection isn’t ready that’s why the server member field is only initialized here when it’s actually ready if we already have a location we should send a user location update one we have once we have the socket Connection in place the connection is single threaded as I mentioned before there is this it method is similar to is EDT and indicates if the current thread is the one managed by the easy thread if not we use the run runnable which invokes the Target runnable on the easy thread similarly to call serially if the values didn’t change since last update so we do nothing we don’t update too much there is a chance we’ll miss an update here but it’s probably not a deal breaker if a user didn’t move much we create a byte array output stream into which we construct the message that we received on the server with the header location Etc I currently hard coded a one kilometer search radius and find explicitly that we aren’t in taxi hailing mode one line to actually send the binary data it would be similar with text Data with the exception of passing overhead the IR exception isn’t likely as this is a ram-based stream the here we received the messages sent from the server specifically driver search result we store user instances in a map where the user ID is the key this saves us from sending duplicate core added events and allows us to just mutate the user properties which other code can observe using the built-in listeners and properties notice that this code is running on the websocket thread so events need to go back into the EDT to prevent potential issues this is really important we need to handle errors properly in a websocket application otherwise a failure can leave us without a connection the Callback interface is Trivial it’s mostly used as a Lambda expression in the code and that’s it for the location service