Replace the <fragment> tag with FragmentContainerView. FragmentContainerView replaces the <fragment> tag as the preferred way of adding fragments via XML. Unlike the <fragment> tag, FragmentContainerView uses a normal `FragmentTransaction` under the hood to add the initial fragment, allowing further FragmentTransaction operations on the FragmentContainerView and providing a consistent timing for lifecycle events.

The resource `R.dimen.activity_horizontal_margin` appears to be unused Unused resources make applications larger and slow down builds. The unused resource check can ignore tests. If you want to include resources that are only referenced from tests, consider packaging them in a test source set instead. You can include test sources in the unused resource check by setting the system property lint.unused-resources.include-tests =true, and to exclude them (usually for performance reasons), use lint.unused-resources.exclude-tests =true. ,

The resource `R.dimen.activity_vertical_margin` appears to be unused Unused resources make applications larger and slow down builds. The unused resource check can ignore tests. If you want to include resources that are only referenced from tests, consider packaging them in a test source set instead. You can include test sources in the unused resource check by setting the system property lint.unused-resources.include-tests =true, and to exclude them (usually for performance reasons), use lint.unused-resources.exclude-tests =true. ,

The resource `R.string.hello_second_fragment` appears to be unused Unused resources make applications larger and slow down builds. The unused resource check can ignore tests. If you want to include resources that are only referenced from tests, consider packaging them in a test source set instead. You can include test sources in the unused resource check by setting the system property lint.unused-resources.include-tests =true, and to exclude them (usually for performance reasons), use lint.unused-resources.exclude-tests =true. ,

The application adaptive icon is missing a monochrome tag If `android:roundIcon` and `android:icon` are both in your manifest, you must either remove the reference to `android:roundIcon` if it is not needed; or, supply the monochrome icon in the drawable defined by the `android:roundIcon` and `android:icon` attribute. For example, if `android:roundIcon` and `android:icon` are both in the manifest, a launcher might choose to use `android:roundIcon` over `android:icon` to display the adaptive app icon. Therefore, your themed application iconwill not show if your monochrome attribute is not also specified in `android:roundIcon`.

The application adaptive roundIcon is missing a monochrome tag If `android:roundIcon` and `android:icon` are both in your manifest, you must either remove the reference to `android:roundIcon` if it is not needed; or, supply the monochrome icon in the drawable defined by the `android:roundIcon` and `android:icon` attribute. For example, if `android:roundIcon` and `android:icon` are both in the manifest, a launcher might choose to use `android:roundIcon` over `android:icon` to display the adaptive app icon. Therefore, your themed application iconwill not show if your monochrome attribute is not also specified in `android:roundIcon`.

Missing `contentDescription` attribute on image Non-textual widgets like ImageViews and ImageButtons should use the `contentDescription` attribute to specify a textual description of the widget such that screen readers and other accessibility tools can adequately describe the user interface. Note that elements in application screens that are purely decorative and do not provide any content or enable a user action should not have accessibility content descriptions. In this case, set their descriptions to `@null`. If your app's minSdkVersion is 16 or higher, you can instead set these graphical elements' `android:importantForAccessibility` attributes to `no`. Note that for text fields, you should not set both the `hint` and the `contentDescription` attributes since the hint will never be shown. Just set the `hint`.

The project references RTL attributes, but does not explicitly enable or disable RTL support with `android:supportsRtl` in the manifest To enable right-to-left support, when running on API 17 and higher, you must set the `android:supportsRtl` attribute in the manifest `<application>` element. If you have started adding RTL attributes, but have not yet finished the migration, you can set the attribute to false to satisfy this lint check.