Updating the Screen

It's about time we see something happen on the screen. 0:01 If we tap on the deck enough, it should eventually become empty and 0:04 switch to the blue card. 0:07 But for that to happen, we need to call our deck views update method 0:09 inside main activities update method. 0:13 Let's start in main activity, by creating a new 0:15 mutable variable at the top of the class to represent our deck view. 0:18 Var deckView. 0:23 And for the type, let's specify DeckView?. 0:28 Right when MainActivity is initialized, we don't yet have a context. 0:32 And we definitely haven't called on create yet. 0:38 So there's no way for us to have an instance of DeckView right from the start. 0:41 So we'll set it to null for now. 0:46 Now that we've got our DeckView property, 0:49 let's set it equal to our DeckView function. 0:51 And then inside the update function and main activity, let's call deckView.update. 1:00 And now we need to decide whether to use a safe call or a non null asserted call. 1:10 This update function is triggered by the game presenter whenever a user takes 1:15 an action, and users can only take actions on views. 1:19 Which means at this point, the views should exist so we should be fine and 1:24 asserting that our deck view is not normal. 1:28 All right now let's run the app. 1:33 And then tap the deck a bunch of times, AKA, exactly 24 times. 1:36 And there we go, we've emptied the deck and we see the blue card. 1:49 One more tap, and we've recycled the waste pile into the deck. 1:54 Now that we've got our deck view out of the way, let's move on to our waste pile. 2:00 Let's create a new class named waste pile view. 2:04 And then let's make it extend image view. 2:17 And then let's add the context parameter just like we had to do last time. 2:23 Next, let's add our init function. 2:38 And inside, let's set the imageResource to our emptyPileDrawable. 2:43 Then, we just need to add an onClick listener. 2:51 And inside, all we need to do is call GamePresenter.onWasteTap. 2:55 With our new function finished, it's time to move on to the update function. 3:00 Let's type fun update, and add our brackets. 3:07 And inside this function, if there are cards in the waste pile, 3:12 we need to show the top card. 3:16 Otherwise we need to show an empty pile. 3:18 Let's start by getting a list of which cards are in the waste pile with. 3:21 Val cards equals game model .waste pile. 3:25 Then let's set image resource Equal to the result of 3:31 if (cards.size > 0 and 3:37 then let's type two spaces for now and 3:42 then add our else and if it is equal to zero it should show the emptyPileDrawable. 3:47 Now we just need to find a way to get the right image resource for a card. 3:53 So back in our two spaces, 3:58 let's call a function that doesn't exist yet 4:01 called getResIdForCard(cards.last()). 4:07 Then let's use Alt+Enter to create this method. 4:13 And let's change the parameter name from last to card. 4:19 Inside this function we're going to need to be able to tell 4:23 Android the name of the resource we want to show. 4:25 Luckily, our resources have nice predictable names. 4:29 They're all the word card followed by the suit followed by the value. 4:33 So let's start by creating a new val named resource name. 4:41 And let's set it equal to, and quotes, the word card. 4:47 Followed by a string template to get the card suit. 4:53 Card.suit. 4:59 And then another string template for 5:01 the cards value, which we want to get by using our cards map. 5:03 So cardsMap[card.value]. 5:09 Finally, at the end, let's add a call to 5:17 .toLowerCase, to make sure that everything matches. 5:20 Then, on the next line, let's return 5:26 context.resources.getIdentifier, and 5:31 then pass in the resource name for the name 5:37 drawable as a string for the type, And 5:46 context.packageName for the package, nice. 5:52 We're probably going to want this to getResIdForCard method and 6:00 more than just this one class. 6:04 So instead of having this method be private to our waste pile view, 6:06 let's get rid of the private keyword. 6:11 And then cut this function and paste it into main 6:16 activity, below our empty pile drawable. 6:22 For the last step, since it's our views that need the resource ID's let's make 6:27 this an extension function on view. 6:31 And there we go back and wastePileView all we have left is adding our 6:36 Ankle View call just like we did with our DeckView, but before we get to that. 6:41 Let's take another look at our DeckView. 6:47 At the bottom of our DeckView, we have the DeckView factory, 6:51 where we take in a context and return an instance of deck view. 6:54 And just like any other lambda expression with one parameter, 6:59 we are allowed to omit that parameter and instead just use the it keyword. 7:02 Well not exactly. 7:13 We can only do that if Cullen is able to figure out what it is, 7:15 and Cullen can't do that here. 7:20 But what we can do is cut this lambda expression, and 7:23 paste it in as the first parameter to anko view. 7:27 This first parameter is a function with one context parameter. 7:32 So here, it has to be a context and everything works. 7:37 Meaning we no longer need our deck view factory, sweet. 7:42 Now, to finish out our waste pile view let's copy this ankoView view from 7:48 deckView, and then in our wastePileView, let's paste it in below the class. 7:53 Then let's change the function name from deckView to wastePileView. 8:02 And change the init function to be an extension function on WastePileView. 8:08 And lastly, 8:14 let's change the factory function to return an instance of WastePileView. 8:15 Now that we've finished our WastePileView, let's head back to main activity and 8:20 create a new property to store it. 8:24 Let's create it right below deck view And name it wastePileView. 8:28 Give it a type of WastePileView?, and set it equal to null. 8:35 Then inside our layout let's delete the imageView below our deck view And 8:41 then set our new wastePileView property equal to our new wastePileView. 8:47 Then let's add a call to lparams and pass in the code dimensions. 8:55 Finally, inside the update method lets add 9:05 a null asserted call to wastePileView.update. 9:09 Now, if we run the app we should be able to click on the deck and 9:13 see our waste pile start updating. 9:17 Looks great. 9:22