Task 6: Make your app interactive

Step 2: Show a toast

In this step, you will attach a Java method to the Toast button to show a toast when the user presses the button. A toast is a short message that appears briefly at the bottom of the screen.

1. Open FirstFragment.java (app > java > com.example.android.myfirstapp > FirstFragment).

This class has only two methods, onCreateView() and onViewCreated(). These methods execute when the fragment starts.

As mentioned earlier, the id for a view helps you identify that view distinctly from other views. Using the findViewByID() method, your code can find the random_button using its id, R.id.random_button. 

2. Take a look at onViewCreated(). It sets up a click listener for the random_button, which was originally created as the Next button.

view.findViewById(R.id.random_button).setOnClickListener(new View.OnClickListener() {

   @Override

   public void onClick(View view) {

       NavHostFragment.findNavController(FirstFragment.this)

               .navigate(R.id.action_FirstFragment_to_SecondFragment);

   }

});

Here is what this code does:

• Use the findViewById() method with the id of the desired view as an argument, then set a click listener on that view.

• In the body of the click listener, use an action, which in this case is for navigating to another fragment, and navigate there. (You will learn about that later.)

3. Just below that click listener, add code to set up a click listener for the toast_button, which creates and displays a toast. Here is the code:

view.findViewById(R.id.toast_button).setOnClickListener(new View.OnClickListener() {

   @Override

   public void onClick(View view) {

       Toast myToast = Toast.makeText(getActivity(), "Hello toast!", Toast.LENGTH_SHORT);

       myToast.show();

   }

});

Step 4: Cache the TextView for repeated use

You could call findViewById() in countMe() to find showCountTextView. However, countMe() is called every time the button is clicked, and findViewById() is a relatively time consuming method to call. So it is better to find the view once and cache it.

1. In the FirstFragment class before any methods, add a member variable for showCountTextView of type TextView.

TextView showCountTextView;

2. In onCreateView(), you will call findViewById() to get the TextView that shows the count. The findViewById() method must be called on a View where the search for the requested ID should start, so assign the layout view that is currently returned to a new variable, fragmentFirstLayout, instead.

// Inflate the layout for this fragment

View fragmentFirstLayout = inflater.inflate(R.layout.fragment_first, container, false);

3. Call findViewById() on fragmentFirstLayout, and specify the id of the view to find, textview_first. Cache that value in showCountTextView.

   ...

    // Get the count text view

    showCountTextView = fragmentFirstLayout.findViewById(R.id.textview_first);

4. Return fragmentFirstLayout from onCreateView().

return fragmentFirstLayout;

Here is the whole method and the declaration of showCountTextView:

TextView showCountTextView;

@Override

public View onCreateView(

       LayoutInflater inflater, ViewGroup container,

       Bundle savedInstanceState

) {

   binding = FragmentFirstBinding.inflate(inflater, container, false);

   binding.getRoot();

   // Inflate the layout for this fragment

   View fragmentFirstLayout = inflater.inflate(R.layout.fragment_first, container, false);

   // Get the count text view

   showCountTextView = fragmentFirstLayout.findViewById(R.id.textview_first);

   return fragmentFirstLayout;

}