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Welcome back.

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In September 2019,

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Google released version 1.0.0

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of two libraries that can make working with activities and fragments easier

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when using jetpack components.

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To use them, we'll add another dependency to our build.gradle file,

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the module one not the project one.

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The current release of this library is now 1.2.4

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but a later version may be available for you.

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A good place to learn about these jetpack libraries

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and keep track of the version is Google's jetpack pages.

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It's worth bookmarking the main jetpack page

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then checking regularly to see what's changed.

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Jetpack has been continually developed

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and new libraries and features are being added all the time.

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The note, a short way down the page is important.

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We can't compile code that uses this library

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if we're compiling to java 7.

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We have to specify java 8.

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We do that by adding an entry in the android section

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of build.gradle.

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Make sure you sync now before moving on.

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Okay. How does that help us?

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It lets us simplify the way we create our view model instances.

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I'll change both activities first

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because I want to draw your attention to an important difference with fragments.

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The change in durations report is the same.

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Be careful with your fragments.

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If you use exactly the same code in fragment,

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it's equivalent to passing this to the ViewModelProvider constructor.

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If we want to share the activities view model,

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we have to use a slightly different form.

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I'll change AddEditFragment first.

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Note that we use by ActivityViewModels not ViewModels.

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That ensures that we get the instance of the ActivitiesViewModel

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equivalent to passing activity on the commented outline above.

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I'll make the same change in MainActivityFragment.

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While we're dealing with this library,

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switch back to the document we were just looking at.

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Scroll down to the version 1.2.0 section

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and have a look at the top important changes since 1.1.0.

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Google have added a FragmentContainerView

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which is now the strongly recommended container

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for hosting our fragments.

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If they strongly recommend it and we're still at the stage of testing and developing our app.

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It's a good idea to use one.

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Back in android studio

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edit the content_mainlayout

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in res/layouts.

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At the moment, this new container doesn't appear in the palette.

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I'm sure Google will add it in there at some point.

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But as we've already got our frame layout and all its attributes configured,

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I'll edit the xml instead.

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Replace frame layout with the new container.

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Notice that android studio changes the closing tag as well.

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Changing the fragment tag is easier

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because a light bulb will do that for us.

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In fact, Google have changed the tool tip and we can choose the action from that.

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Back in the DesignView,

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nothing much changes.

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This new fragment container widget was only added in January 2020,

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and android studio's layout designer doesn't yet have support for rendering it.

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If you're using a later version of android studio,

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you may see it rendered differently.

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At the moment, there's also a rendering error.

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Click the information icon at the top right of the design pane,

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and you might see the message failed to instantiate one or more classes.

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If you do get that message, you can ignore it.

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It's a bug and it'll be fixed in version 1.3.0 of the library.

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The app will run fine.

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The bug only affects the designer when it tries to render the new widget.

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We do have to make a change in our main activity code.

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We've got a couple of errors after changing the widget.

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The widget works much better than the old fragment container,

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and there's now no need to use its view attribute to change visibility.

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Delete .view in the three places where we change the visibility.

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That's on line 60 in OnCreate.

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On line 77, in the ShowEditPane function

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and the third place is in the RemoveEditPane function.

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Back in the browser find androidx.activity

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in the list on the left.

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I won't scroll through the document but check the notes

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for version 1.0.0.

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The activity-ktx module is automatically included

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when we use fragment-ktx,

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if your app doesn't use fragments,

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you can set the dependency to androidx.activity

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:activity-ktx instead.

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You can see that in the declaring dependencies example

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at the top of the page.

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All right. We're now up to date,

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and we're getting our ViewModel instances

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in a more Kotlin-like way.

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We've also seen the jetpack documentation.

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It's a great resource to check to find out about new things

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that Google are doing with the jetpack,

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a.k.a androidx libraries.

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We're now really 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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to make sure we haven't broken anything. I'll see you there.