WEBVTT 00:00.080 --> 00:00.960 Welcome back. 00:01.200 --> 00:05.400 Let's run our application and go to Firebase Console. 00:05.400 --> 00:08.240 Select Firestore Database. 00:08.240 --> 00:15.800 And inside the markers collection we have three markers Italy Paris and San Francisco. 00:15.840 --> 00:21.160 We have an error here in the view model argument type mismatch. 00:21.200 --> 00:22.920 Actual type is a flow. 00:22.920 --> 00:28.480 But collection which is a list of destination marker was expected. 00:28.600 --> 00:35.720 Since we changed the type to flow list of destination, we need to change the view model. 00:35.720 --> 00:37.840 So we updated the repository. 00:37.880 --> 00:40.160 With the new implementation of flow. 00:40.320 --> 00:44.160 We should update the view model here. 00:44.320 --> 00:51.720 Inside this function load markers from Firestore we need to update the code. 00:51.760 --> 00:59.320 Keep the markers which is a snapshot state list destination marker mutable state list of and. 00:59.320 --> 01:04.480 Here let me introduce a new variable called Listener Active. 01:04.680 --> 01:11.520 This is a boolean just to check if it is active or not, and we control it. 01:11.520 --> 01:16.400 And here if listener active then return. 01:16.440 --> 01:21.160 Otherwise continue with the ViewModel scoop dot launch here. 01:21.360 --> 01:27.720 Remove the try catch because we used the listener active and inside it. 01:27.920 --> 01:32.240 Start with marker repository dot. 01:32.440 --> 01:41.560 Get all markers from Firestore dot collect latest and set the new markers. 01:41.680 --> 01:44.800 Markers dot clear and add all markers. 01:44.800 --> 01:52.360 Remove these codes and outside launch set the listener active equals to true. 01:52.400 --> 01:53.680 Let me explain. 01:53.680 --> 01:59.560 In this code we are listening for real time updates from a data stream. 01:59.680 --> 02:07.440 Firestore in an Android ViewModel while managing the listener state to avoid duplicate subscriptions. 02:07.440 --> 02:17.090 This function subscribes to a stream of marker data from Firestore updates the local markers list whenever 02:17.090 --> 02:23.330 new data arrives, and ensures only one active listener exists at a time. 02:23.570 --> 02:33.090 So listener active, and this is a very important variable that will fetch the state of a listener. 02:33.250 --> 02:36.730 So this is a Boolean flag tracking. 02:36.810 --> 02:40.330 Tracking whether a listener is already running. 02:40.490 --> 02:43.090 Prevents duplicate subscriptions. 02:43.090 --> 02:49.810 If the function is called multiple times and the ViewModel scope uses the Viewmodels coroutine scope. 02:49.850 --> 02:56.490 ViewModel with which automatically cancels when the ViewModel is cleared. 02:56.610 --> 03:01.170 Ensuring the listener doesn't leak when the ViewModel is destroyed. 03:01.370 --> 03:03.970 Get all markers from stream. 03:04.130 --> 03:11.690 Cancels the previous collection if a new data arrives before the previous emission is preceded, and 03:11.690 --> 03:16.330 the process only processes that latest data. 03:16.370 --> 03:18.810 Avoiding black backlog. 03:18.850 --> 03:21.450 Build up markers dot clear. 03:21.490 --> 03:24.850 Resets the existing list markers. 03:24.850 --> 03:28.770 Dot add all replaces with fresh data. 03:28.770 --> 03:31.650 Set the listener state to active. 03:31.770 --> 03:37.730 Marks the listener as active to prevent redundant subscriptions. 03:37.730 --> 03:40.450 So why collect latest. 03:40.490 --> 03:47.210 Collect latest ideal for UI updates where only the latest data matters. 03:47.210 --> 03:48.810 For example the map markers. 03:48.810 --> 03:57.010 In this case, if a new data arrives while processing the current emission, it cancels the current 03:57.010 --> 04:00.490 work and restarts with the new data. 04:00.530 --> 04:05.890 Use collect if you need to process every emission sequentially. 04:06.050 --> 04:09.610 The thread safety markers list should be thread safe. 04:09.610 --> 04:12.610 Collection accessed from multiple threads. 04:12.850 --> 04:19.250 And for this we used the markers list which is a snapshot state list. 04:19.290 --> 04:25.690 Okay, so this is our ViewModel and this is our load markers from Firestore. 04:25.890 --> 04:29.530 Now let's run our application in Firestore. 04:29.570 --> 04:37.370 We have three markers Italy Paris France and San Francisco Italy Paris and San Francisco. 04:37.410 --> 04:41.170 Now let's add a new marker here. 04:41.330 --> 04:46.290 Change the the viewing to window. 04:46.490 --> 04:49.690 And here let me show you. 04:49.930 --> 04:50.890 This is better. 04:50.930 --> 04:51.410 Okay. 04:51.810 --> 04:56.050 Now please, guys, watch the magic. 04:56.210 --> 05:00.930 Add a new document, which is a new coordinates for a marker. 05:01.250 --> 05:04.970 And set the marker ID, for example. 05:05.130 --> 05:08.890 Um, the field ID or. 05:09.410 --> 05:11.650 No need to specify the id. 05:11.730 --> 05:16.610 We can start directly with latitude and longitude. 05:16.610 --> 05:19.450 So latitude which is a number. 05:19.730 --> 05:30.090 Set the value 51.5072 and the longitude field longitude. 05:30.090 --> 05:39.540 Please pay attention If you, uh, make any mistake here, it will not get the correct ID and the correct 05:39.540 --> 05:41.180 longitude and latitude. 05:41.220 --> 05:52.460 Okay, so longitude, which is of type number set the value to -0.1276. 05:52.460 --> 05:56.500 Please pay attention here our map. 05:56.500 --> 06:02.180 If I click save there would be a new marker in United Kingdom. 06:02.180 --> 06:03.260 And here we go. 06:03.300 --> 06:10.540 You see guys that this is the power of listening real time updates. 06:10.540 --> 06:18.580 And get the latest and updated and real time data from Firebase Firestore database. 06:18.620 --> 06:19.540 Okay guys. 06:19.540 --> 06:21.260 So congratulations. 06:21.260 --> 06:29.820 We succeeded in getting data and getting the real time and updated data from Firestore.