1 00:00:05,150 --> 00:00:06,150 Welcome back. 2 00:00:06,950 --> 00:00:09,950 Having those buttons in the RecyclerView looks untidy, 3 00:00:10,250 --> 00:00:12,850 and it doesn't fit with modern user interfaces. 4 00:00:13,550 --> 00:00:16,850 Users are used to removing items by swiping them left. 5 00:00:17,650 --> 00:00:19,350 That's not very hard to implement, 6 00:00:19,710 --> 00:00:22,510 and we'll see how to do that in the next few videos. 7 00:00:24,110 --> 00:00:26,410 We could use a gesture detector, 8 00:00:26,410 --> 00:00:29,610 and we've seen how those work in the FlickrBrowserApp. 9 00:00:30,110 --> 00:00:33,310 But for this app, I'm going to use an ItemTouch helper. 10 00:00:33,810 --> 00:00:36,510 We'll check for swipes in MainActivityFragment. 11 00:00:37,210 --> 00:00:39,210 You set up an ItemTouchHelper 12 00:00:39,460 --> 00:00:41,460 then attach it to your RecyclerView. 13 00:00:42,160 --> 00:00:44,360 I'll do that in OnViewCreated. 14 00:01:03,860 --> 00:01:06,060 That's where we configure the RecycleView. 15 00:01:06,460 --> 00:01:10,460 So it makes sense to attach the ItemTouchHelper in there too. 16 00:01:10,960 --> 00:01:12,860 Accept the import from 17 00:01:12,860 --> 00:01:16,740 androidx.RecyclerView.widget.itemtouchhelper 18 00:01:17,040 --> 00:01:18,840 if it's not imported automatically. 19 00:01:19,500 --> 00:01:22,860 The ItemTouchHelper will replace the delete buttons 20 00:01:22,860 --> 00:01:24,160 OnClickListener, 21 00:01:24,820 --> 00:01:27,420 that's in our adapter and we'll have a look at that in a moment. 22 00:01:27,920 --> 00:01:29,280 But first we've got an error. 23 00:01:29,940 --> 00:01:33,930 When we call OnDelete click, on line 77, 24 00:01:34,180 --> 00:01:37,480 we need to give it a task, but we don't know the task. 25 00:01:38,080 --> 00:01:40,980 The adapter does or more precisely 26 00:01:40,980 --> 00:01:43,580 the adapter's ViewHolder class does. 27 00:01:44,910 --> 00:01:48,510 That's where we're getting the task from on line 76. 28 00:01:49,170 --> 00:01:53,170 To fix the error, we need to make the ViewHoldersTask available. 29 00:01:53,870 --> 00:01:56,870 That's one of the few changes we have to make in the adapter. 30 00:01:57,370 --> 00:02:00,570 So let's have a look at our CursorRecyclerViewAdapter class. 31 00:02:07,230 --> 00:02:10,229 We defined our ViewHolder at the start of the file 32 00:02:10,229 --> 00:02:11,730 up on line 17. 33 00:02:12,130 --> 00:02:15,130 It gets passed a task in its bind function, 34 00:02:15,630 --> 00:02:18,630 and we need to make that available as a class attribute. 35 00:02:34,430 --> 00:02:37,530 The ViewHolder won't be displayed in the RecyclerView until 36 00:02:37,530 --> 00:02:39,890 after its bind function has been called, 37 00:02:40,390 --> 00:02:42,790 that means we can use late init there 38 00:02:42,790 --> 00:02:44,790 rather than using a nullable type. 39 00:02:45,490 --> 00:02:49,490 Our task attribute will get its value when the bind function is called. 40 00:03:00,490 --> 00:03:02,490 We're going to remove the delete button. 41 00:03:02,490 --> 00:03:05,740 There's no point leaving it in the layout when we're going to be swiping. 42 00:03:06,400 --> 00:03:09,760 That means we'll no longer be able to refer to it in our ViewHolder. 43 00:03:10,120 --> 00:03:11,620 So I'll delete it. 44 00:03:15,870 --> 00:03:20,270 There's also no need to set its OnClickListener and we can delete those lines. 45 00:03:28,520 --> 00:03:31,020 If we're no longer setting the DeleteListener, 46 00:03:31,020 --> 00:03:35,320 there's no need to have it in our interface. So I'll remove that as well. 47 00:03:42,320 --> 00:03:46,320 The final change is in the OnBindViewHolder function 48 00:03:46,820 --> 00:03:48,320 where we hide the delete button. 49 00:03:48,820 --> 00:03:50,420 We don't need that line either. 50 00:03:56,220 --> 00:03:58,420 That's all the changes to our adapter. 51 00:03:58,420 --> 00:04:01,020 Close it, and return to MainActivityFragment. 52 00:04:04,020 --> 00:04:06,520 We fixed the error, and now we've got a task 53 00:04:06,520 --> 00:04:09,120 to pass to the OnDeleteClick function. 54 00:04:09,780 --> 00:04:12,380 We've got another error but I'll come to that soon. So what's going on here? 55 00:04:14,940 --> 00:04:16,540 This is boilerplate code. 56 00:04:17,040 --> 00:04:20,640 When you want to attach an ItemTouchHelper to a RecyclerView, 57 00:04:21,140 --> 00:04:22,740 this is the standard code to do it. 58 00:04:23,620 --> 00:04:27,520 Our ItemTouchHelper contains an object of type 59 00:04:27,520 --> 00:04:30,820 ItemTouchHelper.SimpleCallback. 60 00:04:31,480 --> 00:04:35,680 SimpleCallback creates a callback for drag and swipe operations. 61 00:04:36,180 --> 00:04:40,480 Callback is an abstract class and we have to provide implementations 62 00:04:40,480 --> 00:04:41,780 for two functions, 63 00:04:42,080 --> 00:04:44,080 OnMove and OnSwiped. 64 00:04:44,880 --> 00:04:49,380 OnMove is used if you want to allow the recycler items to be dragged up and down. 65 00:04:50,180 --> 00:04:52,840 OnSwiped is where you define the behavior you want 66 00:04:52,840 --> 00:04:54,340 when the item's swiped, 67 00:04:54,640 --> 00:04:56,040 and that's what we're doing here. 68 00:04:56,440 --> 00:05:00,040 Our code is simple if the item swiped left, 69 00:05:00,840 --> 00:05:02,840 which we check on line 75, 70 00:05:03,340 --> 00:05:07,140 then we'll pass the ViewHolders task to OnDeleteClick. 71 00:05:07,940 --> 00:05:11,940 That's our ItemTouchHelper written. But there's one more step we need to do, 72 00:05:12,740 --> 00:05:14,940 we need to attach it to the RecyclerView. 73 00:05:15,440 --> 00:05:18,000 Otherwise, it won't be used when the items are swiped. 74 00:05:33,450 --> 00:05:37,950 Line 82 attaches our ItemTouchListener to the RecyclerView. 75 00:05:38,610 --> 00:05:41,810 Before we can test it, we need to fix the error 76 00:05:41,810 --> 00:05:43,310 in OnDeleteClicked 77 00:05:43,970 --> 00:05:45,670 on line 89. 78 00:05:46,330 --> 00:05:49,690 We've got an error because we removed this function from the interface. 79 00:05:50,350 --> 00:05:54,550 It's no longer overriding anything, so we have to remove the override. 80 00:05:58,150 --> 00:06:00,400 All right. The moment of truth. 81 00:06:00,800 --> 00:06:04,160 Let's see if we can delete tasks by swiping them left. 82 00:06:05,060 --> 00:06:07,260 Run the app, and swipe some tasks. 83 00:06:13,060 --> 00:06:17,270 To swipe in the emulators, you need to click the object to swipe 84 00:06:17,270 --> 00:06:18,770 then flick the mouse left. 85 00:06:19,570 --> 00:06:21,570 Make sure you swipe all the way. 86 00:06:22,070 --> 00:06:26,570 If you only sort of swipe halfway, the animation puts the item back in the list. 87 00:06:27,230 --> 00:06:30,480 It's much easier to do on a physical device with your finger 88 00:06:30,480 --> 00:06:32,480 rather than using a mouse in an emulator. 89 00:06:33,780 --> 00:06:37,140 That's looking good. We've got our confirmation dialog. 90 00:06:37,740 --> 00:06:40,540 I'll tap delete and the task's deleted. 91 00:06:42,200 --> 00:06:44,800 That wasn't a lot of work to implement swiping. 92 00:06:45,100 --> 00:06:47,200 We added a simple TouchHelper 93 00:06:47,200 --> 00:06:49,200 and attached it to the RecyclerView. 94 00:06:50,000 --> 00:06:51,500 And it almost works. 95 00:06:52,300 --> 00:06:53,300 There's a problem. 96 00:06:53,600 --> 00:06:56,800 To demonstrate it, I'll choose task 6. 97 00:06:57,790 --> 00:07:01,690 Make a mental note of the task number and then swipe it. 98 00:07:03,590 --> 00:07:06,590 When the dialog appears, tap cancel. 99 00:07:08,290 --> 00:07:11,550 That looks worrying, but it's normal behavior. 100 00:07:11,550 --> 00:07:14,150 The task hasn't been deleted from the database. 101 00:07:14,150 --> 00:07:17,350 We can confirm that by refreshing the activity. 102 00:07:17,900 --> 00:07:20,500 Rotating the device is an easy way to do that. 103 00:07:30,500 --> 00:07:33,500 When the recycler redraws we get our task back. 104 00:07:34,300 --> 00:07:36,900 As I said that's normal behavior. 105 00:07:37,400 --> 00:07:40,300 When you swipe something an animation runs 106 00:07:40,300 --> 00:07:42,300 and it gets removed from the RecycleView. 107 00:07:43,200 --> 00:07:46,200 In the next video, we'll see how to reverse that 108 00:07:46,500 --> 00:07:49,900 to get our task back if the user cancels the delete. 109 00:07:50,560 --> 00:07:51,460 I'll see you there.