Awesome, now it's time to assign values to these new variables.

Let's start by adding four new lines to the bottom of onCreate.

Then on the second new line, let's add a comment, // Assign

the Views from the layout file to the corresponding variables.

It's important that don't assign the views until after the call to setContentView.

If we try to access a view from our layout before calling setContentView,

it won't exist and we'll get an error.

On the next line, let's start typing factTextView =.

And now, what we need is a method that will take in the ID that we've set in

the layout, and return our TextView.

Fortunately, every activity has a method for this, and it's called findViewByID.

Let's start typing findViewByID after the equals sign.

And notice that as you're typing,

the autocomplete feature is filling it in below.

Android Studio analyzes what we're typing, and

offers suggestions that match what we've typed so far.

Automatic code completion is awesome.

It's super convenient, and it makes it so that we only need to remember the first

few letters of something, and Android Studio will take care of the rest.

Now we can either finish typing this method, or

we can just hit Enter to select it from code completion.

And now we see a hint about the parameter we need to use here.

The findViewByID method requires an ID as its parameter.

But rather than just type in the ID from the layout,

we must refer to it through a generated resource class.

When we built our project, Android automatically builds a class for

us called simply R, which stands for resources.

This class contains all the IDs of our files and

the res directory, as well as a ton of other default resource IDs.

If we open the project pane and switch to the project perspective.

And then drill into app > build >

generated > src > r > debug > and

then our package name, we can even open the R class.

Though notice at the top, there's a warning saying,

Files under the build folder are generated and should not be edited.

We're not here to edit anything.

It's just nice to know where the R class comes from.

Let's close this and switch back to the Android perspective.

And I'll hide the project pane again.

Back in FunFactsActivity.java let's type R.

Then we need to pick which type of resources we're looking for.

Since we're looking for an ID, let's type id followed by another dot.

And look at that, it's showing the IDs that we set in our layout.

Let's pick factTextView, and hit Enter to select it, and semicolon.

That seems like it should've been enough, but

that red error line is letting us know that something is wrong.

If we hover over it, we can see that it says incompatible types.

factTextView requires a TextView, but we're setting it to a view.

One way Android could've solved this would be by providing a find method for

every type of view.

So maybe there would be a findTextViewById method and a findButtonById method.

But that would be a ton of methods.

Instead, because a TextView is just a specialized view, or

a subclass of View, we can fix this with something known as a cast.

A cast allows us at say that one data type, in this case, the generic

view returned by the method, can be safely considered to another data type.

In this case, a TextView.

Since we know the view returned for this ID will in fact be a TextView,

all we need to do is cast this view to a TextView, by putting the name

TextView in parentheses in front of our method call, like this.

Another way we could've fixed this is by using Android Studio's quick fix feature.

Let's undo the cast by hitting Ctrl+Z on Windows or Cmd+Z on Mac.

Then, if we place our cursor on the code with the error and

hit Alt + Enter, we're presented with a list of quick fixes.

The first one is the cast we're looking for.

Hit Enter to select it.

And there we go, Android Studio did the cast for us.

Now that our cast is complete and

our error is gone, let's move on to our button.

It's pretty much the same code, but remember that the ID is different and

we'll need to cast it into a button instead of a TextView.

Let's try adding it as a code challenge.