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Welcome back.

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Shortly after we developed the changes for the videos in this section,

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Google made another change.

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In fact we've made several updates to this section

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because of changes in the time between developing the code

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and recording the videos.

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That's how quickly things change in this environment.

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I'm making this video because of a change that affects our AppDialog class.

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We've got a serious warning in AppDialog

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on line 65. This change is quite a good one

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because it means we can use the bang bang operator less often now.

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What google have done is added a

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require context method to the AndroidxFragment class.

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We've already established that the context can't be null

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at this point in our code.

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But we still had to use the bang bang operator,

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so the compiler would compile the code.

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I don't like using bang bang. I hope you don't either.

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Google have now given us an alternative.

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Click on context on line 65,

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and accept the tool tip suggestion to replace with

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requireContext.

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This removes the need to use bang bang.

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But be very careful here,

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if the context had been null at this point then our code would have crashed.

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Using context bang bang didn't prevent the code from crashing

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it was a way for us to let the compiler know that the context

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wouldn't be null.

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We were sure context couldn't be null.

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Using require context does the same thing.

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If the context is null, our code will crash.

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The RequireContext function will throw in

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illegal state exception if the context is null.

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All we've really done is replace one exception with another.

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We'll now get illegal state exception

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whereas before we would have got null pointer exception.

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Using RequiredContext doesn't somehow magically give us a context

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when one isn't available whether we can get a context or not

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depends on where we are in the fragment lifecycle,

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if the fragment isn't attached to its activity context will be null.

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Remember the context is the activity.

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RequireContext just gives us a nicer way to get a context

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while keeping the compiler happy.

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It doesn't prevent the app from crashing

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if we try to use the context before it's available.

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Control click on the RequireContext function

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to view the source code.

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As you can see it throws an exception if the context is null.

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All we've done is appease the compiler without having to use bang bang.

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It's still our responsibility

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to ensure that we don't try to use the context if it might be null.

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I'll say that again, using RequireContext

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doesn't prevent our code from crashing.

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We'll get a more useful error message, that's all.

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As you can see in the source code, the error message will tell us that our fragment

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isn't attached to a context.

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We'll still get a crash.

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Apart from the slightly more informative error message,

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the only advantage of using required context

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is that we can avoid using the bang bang operator.

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That can be useful if your source code system runs scripts

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to validate the code you check in and tests for bang bang.

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As you saw, before I made the change, we had a strong warning.

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If you use android studio's source code integration

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that would trigger a warning when you try to check the code in.

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Okay. I don't want to label the point too much.

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I'll finish by talking about a few more required functions that Google

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have added. Have a look through this source file fragment.java

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and you'll find some more require function.

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There's a require activity for when you need to get the

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fragments activity and don't want to use the activity

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further up in this file around line 676.

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There's a RequireArguments function.

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Once again, this doesn't guarantee that arguments isn't null.

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We can't magically create arguments.

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What it does is throw an exception if you try to access the arguments

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when the arguments are null.

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That's useful in our AppDialogue class.

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I'll switch back to it and go to the bottom of the file.

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The code's commented out at the moment

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but, you can see that we use arguments bang bang

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in the OnCancel function.

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When we uncomment that function later,

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we'll also change it to use require arguments.

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I'll leave the change until then but I wanted to mention it now.

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Remember that we've already established that the arguments aren't null.

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We do that in the OnCreateDialog function.

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If there are no arguments, we throw an exception in line 90.

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All right. Now we really are ready to start improving the functionality of our app.

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And we'll start that in the next video.

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Of course, you should run the app and test it

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just to make sure that we haven't broken anything. See you in the next video.