1 00:00:05,150 --> 00:00:06,250 Welcome back, everyone. 2 00:00:06,650 --> 00:00:08,650 Another change we wanted to make 3 00:00:08,650 --> 00:00:11,770 is to update the display when we delete a task 4 00:00:11,770 --> 00:00:13,270 that's currently being timed. 5 00:00:14,470 --> 00:00:18,270 Let's see the problem you're trying to solve then you can have a go at fixing it. 6 00:00:19,150 --> 00:00:21,510 Run the app, and make sure we're not timing anything. 7 00:00:22,610 --> 00:00:26,710 At the top of the screen, we've got the message "No task being timed". 8 00:00:27,590 --> 00:00:29,890 Long tap a task to start timing it. 9 00:00:32,890 --> 00:00:36,880 The display updates and now we're currently timing task 1. 10 00:00:37,280 --> 00:00:41,280 The problem we want to fix is what happens when I swipe the task left 11 00:00:41,640 --> 00:00:42,540 to delete it. 12 00:00:46,340 --> 00:00:49,640 When I do that and tap the delete button to confirm, 13 00:00:51,520 --> 00:00:53,020 the display doesn't change. 14 00:00:53,570 --> 00:00:56,470 We're still currently timing task 1. 15 00:00:56,870 --> 00:00:59,070 Of course, we're not,we just deleted it. 16 00:01:00,870 --> 00:01:01,870 The fix is easy, 17 00:01:02,230 --> 00:01:06,590 and the only change you need to make is in our TaskTimerViewModel. 18 00:01:07,140 --> 00:01:10,440 As long as you've taken the time to understand how all this works 19 00:01:10,800 --> 00:01:14,800 and how MainActivity is observing changes in the ViewModel, 20 00:01:15,050 --> 00:01:17,050 this is an easy change to make. 21 00:01:17,950 --> 00:01:21,950 So your challenge is to fix the code in TaskTimerViewModel 22 00:01:22,250 --> 00:01:26,050 to display the correct message when we delete the task that we're timing. 23 00:01:26,750 --> 00:01:31,110 Pause the video now, and I'll go over my solution when you come back. 24 00:01:36,360 --> 00:01:38,260 Welcome back. How did you get on? 25 00:01:39,060 --> 00:01:42,560 You should have been able to fix the display with just two lines of code 26 00:01:42,560 --> 00:01:44,060 inside a condition. 27 00:01:44,260 --> 00:01:47,460 Let's review how all this works before writing any code. 28 00:01:47,460 --> 00:01:48,760 Open MainActivity. 29 00:02:06,160 --> 00:02:08,759 The display is updated in MainActivity 30 00:02:08,759 --> 00:02:12,760 by observing the timing LiveData object in the ViewModel. 31 00:02:13,120 --> 00:02:15,220 When the ViewModel deletes a task, 32 00:02:15,220 --> 00:02:17,820 it should check to see if the task is being timed. 33 00:02:18,520 --> 00:02:22,720 It can then update its LiveData object to allow MainActivity 34 00:02:22,720 --> 00:02:24,220 to update the display. 35 00:02:25,020 --> 00:02:29,620 We add the code in the TaskTimerViewModel's DeleteTask function. 36 00:03:35,980 --> 00:03:39,340 We're storing the task that's being timed in current timing, 37 00:03:40,140 --> 00:03:43,640 that may be null so we need a safe call operator. 38 00:03:44,440 --> 00:03:46,340 That's on line 135. 39 00:03:47,140 --> 00:03:51,140 If current timing's task ID is the same as the ID of the task 40 00:03:51,140 --> 00:03:52,140 being deleted, 41 00:03:52,640 --> 00:03:55,520 we update the TaskTimingLiveData object. 42 00:03:56,070 --> 00:04:00,370 Setting it to null will let MainActivity know that nothing's being timed. 43 00:04:01,250 --> 00:04:03,550 We also set current timing to null. 44 00:04:03,910 --> 00:04:05,510 If we've just deleted the task 45 00:04:05,910 --> 00:04:08,110 then, we're obviously not still timing it. 46 00:04:08,770 --> 00:04:13,230 I'll go into code, reformat the code, and then run the app again to test it. 47 00:04:25,670 --> 00:04:28,770 StartTiming a task then swipe to delete. 48 00:04:31,770 --> 00:04:35,670 The first test I'll perform is to cancel the deletion. 49 00:04:37,670 --> 00:04:40,870 This should restore the task and we should still be timing it, 50 00:04:41,370 --> 00:04:45,570 tap cancel and the task reappears and it's still being timed, 51 00:04:45,930 --> 00:04:46,830 so that works. 52 00:04:47,820 --> 00:04:52,420 Repeat the operation but this time tap the dialog's delete button. 53 00:04:56,320 --> 00:04:59,320 Task is deleted, and the display updates. 54 00:05:00,120 --> 00:05:02,120 There are other tests you should perform. 55 00:05:02,120 --> 00:05:06,620 Make sure that deleting a task that isn't being timed, also still works. 56 00:05:07,320 --> 00:05:09,820 You'll want to perform that test twice too, 57 00:05:09,820 --> 00:05:12,820 make sure that both the cancel and the delete work 58 00:05:12,820 --> 00:05:14,820 when the confirmation dialog appears. 59 00:05:15,920 --> 00:05:19,120 In the next video, we'll have a look at how we can implement 60 00:05:19,120 --> 00:05:23,580 parameterized queries in SQLite. I'll see you there.