Module 14: Creating a WhatsApp Clone
Transcript
there is still one other class within the model package once we finish that we’ll go to the main class the chat message class is another property business object but one that’s even simpler than the last one this is the author of the message since we use ids and not phones this might become an issue so we need to keep track of both sent to can be important as this message might have been sent to a group and not directly to our current user the timestamp of the message and the actual text of the message are the main payload attachments aren’t fully implemented the general idea is a url of the attachment mapping to a mime type so we can represent it in the ui as image slash video audio or document the list of people who viewed the message which can be more than one for a message sent to a group the typing message is a special type of message that we don’t currently send but it can be sent pretty easily and just update the ui that the user is typing to this chat this is the final property in this class which is relatively simple with that long detour out of the way let’s go back to the main class as you can see i left most of the code intact and kept it as the default the first piece of code you will see that isn’t part of the default code is this line to initialize the server and load the saved data there is also the push interface which we need to implement to receive push callbacks that leads us directly to the first method from that interface we don’t need to implement this method since we use push only as a visual medium and rely on web sockets to carry the actual data push is inherently unreliable and might perform badly it places limitations on the type of data you can send we have more control over web sockets we use push only when the app is minimized the one method we need to implement from the push interface is the registered for push corbett when this callback is invoked we need to send the push key to the server this is important notice that the push key isn’t the device id there are different values don’t confuse them the sms verification class is an abstract class from the sms verification cn1 lib it lets us move some of the functionality of that library into the server the first method is the send sms code method it sends an sms mesh message to the given phone number on the server it invokes the signup call which triggers an sms to that phone number this callback is invoked as part of the signup process when the user types in or the system intercepts a phone number this callback is invoked it sends the verification string to the server side and returns the result based on that the message listener allows us to track messages from the server such as connect incoming messages etc a lot of this isn’t implemented as we don’t need it right now but it could be useful for the ui as it evolves one thing we do implement here is the message received api there isn’t much going on in this method though if the current form is the chat form then we need to check if we are currently in the chat form with the sender of the incoming message assuming this is the case we can add this message to the ui regardless we need to refresh the main ui of the chat list container since the order to the contacts will change next we have the start lifecycle method you will notice that we invoke bind message listener even when we restore a running app as you might recall we close the websocket connection when the app is minimized this effectively restores that connection when the app is restored back to normal the this call happens when the app is launched in a cold start if the phone number isn’t set this is the first activation and we need to set up a new user the activation form api builds the data and you are using a builder pattern where every method adds to the resulting form first we allocate the activation form with the title sign up when we then determine that we want a six digit activation code instead of the default four digit code we finally show the activation ui this accepts two arguments the second argument is the sms verification subclass we discussed earlier it sends the sms details to the server which issues an sms it then performs verification on the server which is more secure than client-side verification the first argument is a callback that’s invoked when the activation is completed it’s invoked with a phone number in the result here we store the new phone number to the preferences then show the main form ui if the user was already registered we show the main form directly we discussed the bind method before so the last piece is the register push core this is an essential part of the push notification support finally we added close websocket code to the stop method this implements the logic of stopping the websocket connection when the app is minimized