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Android Fragments

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Handling Clicks

5:20 with Ben Deitch

In this video we'll see how we can handle clicks in the Fragment and have that trigger an action in the Activity!

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    The last thing we need to do with our list fragment is make it respond to touch. 0:00
    When we tap on a recipe we should change the UI 0:04
    to display a different fragment with the recipe details. 0:07
    And who's responsible for managing these UI changes? 0:10
    That's right, our activity. 0:13
    So when we click a recipe on our list this should call a method in our activity 0:16
    which handles the UI changes. 0:20
    But for now, let's settle for just showing a toast of the recipe's name. 0:22
    A good way to communicate events from a fragment back to its hosting activity, 0:27
    is to define a callback interface inside the fragment, and 0:31
    then have the activity implement this interface. 0:35
    Here's an example. 0:38
    Let's say we've got a fragment with a button and 0:40
    when we tap that button, we want to call a method in the activity. 0:43
    We create an interface with our method inside the fragment class. 0:47
    And the activity implements this interface. 0:51
    Then, we use the getActivity() method to get our activity, and 0:54
    cast it to our interface. 0:58
    Lastly, in the on click method of the button, 1:00
    we call the onButtonClicked method. 1:03
    All right let's start by creating a new interface and our list fragment class. 1:06
    And let's call it onRecipeSelectedInterface. 1:12
    At the top of the class let's add some space and type public 1:16
    interface OnRecipeSelectedInterface and then brackets. 1:22
    Now we need to add a method to our interface. 1:31
    This will be the method that our activity needs to implement 1:34
    to handle a recipe being selected. 1:36
    So let's call it onListRecipeSelected void onListRecipeSelected. 1:39
    And then let's give it an int parameter named index which will represent the index 1:49
    of the chosen recipe. 1:54
    That will do it for the interface next up let's implement this interface and 1:57
    our activity. 2:01
    Over in main activity after we extend AppCompactedActivity 2:03
    let's implement our new interface. 2:08
    Implements OnRecipeSelectectedInterface. 2:11
    Then use Alt+Enter to create our OnRecipeSelected method 2:16
    and to top it off let's toast which recipe was clicked. 2:23
    Toast and make sure to pick the create a new toast option. 2:28
    Then for the second parameter let's use Recipes.names 2:34
    and pass an index for the index. 2:39
    And now we'll see the name of our recipe as a toast when we select it. 2:45
    Moving back to our list fragment class, we need to get the activity and 2:49
    cast it to onRecipeSelectedInterface. 2:53
    So right at the top of onCreateView, let's create a new 2:56
    onRecipeSelectedInterfaceObject named listener. 3:02
    And let's set it equal to our activity, getActivity, and 3:10
    then use Alt+Enter to add the cast. 3:15
    Now that we've got our listener, 3:19
    we just need to call listener.onListRecipeSelected, 3:21
    whenever a recipe is tapped. 3:25
    And since the ListAdapter is where we set the OnClickListeners for 3:27
    each list item, we need to pass our listener into our ListAdapter. 3:31
    So let's just add it right here, and then use Alt+Enter to create the constructor. 3:36
    Next, we need a field for our listener and our ListAdapter class. 3:46
    Inside the constructor, let's type mListener = listener. 3:51
    And then use Alt+Enter on mListener to create our new field. 3:56
    And now that we've got our listener as a field, 4:04
    down in the onClick method of our view holder, all the way at the bottom. 4:08
    Let's call mListener.onListRecipeSelected and pass in the index of this view. 4:15
    Which we don't have yet but it looks like we can get it from the bindView method. 4:23
    Let's create a new field for the index of this view and name it mIndex 4:28
    private int mIndex. 4:33
    Then let's set mIndex and bindView. 4:40
    MIndex = position. 4:46
    And then in onClick let's pass it in to on onListRecipeSelected. 4:51
    All right that should do it. 4:57
    Let's test the app and see if our toasts work. 4:59
    And if we start tapping on list items, we should see some toasts. 5:08
    Like this nice French Toast toast. 5:17

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