(#) Unnecessary leaf layout !!! WARNING: Unnecessary leaf layout This is a warning. Id : `UselessLeaf` Summary : Unnecessary leaf layout Severity : Warning Category : Performance Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : Initial Affects : Resource files Editing : This check runs on the fly in the IDE editor Implementation : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/UselessViewDetector.java) Tests : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/UselessViewDetectorTest.kt) Copyright Year : 2011 A layout that has no children or no background can often be removed (since it is invisible) for a flatter and more efficient layout hierarchy. !!! Tip This lint check has an associated quickfix available in the IDE. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text res/layout/useless.xml:85:Warning: This FrameLayout view is unnecessary (no children, no background, no id, no style) [UselessLeaf] <FrameLayout ----------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `res/layout/useless.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <merge xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" > <!-- Neither parent nor child define background: delete is okay --> <FrameLayout android:id="@+id/LinearLayout" android:layout_width="match_parent" android:layout_height="match_parent" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout> </FrameLayout> <!-- Both define background: cannot be deleted --> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/bg" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/bg" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout> </FrameLayout> <!-- Only child defines background: delete is okay --> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/bg" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout> </FrameLayout> <!-- Only parent defines background: delete is okay --> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/bg" > <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout> </FrameLayout> <!-- Leaf cannot be deleted because it has a background --> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/bg" > </FrameLayout> <!-- Useless leaf --> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" > </FrameLayout> </merge> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/UselessViewDetectorTest.kt) for the unit tests for this check to see additional scenarios. The above example was automatically extracted from the first unit test found for this lint check, `UselessViewDetector.testUseless`. To report a problem with this extracted sample, visit https://issuetracker.google.com/issues/new?component=192708. (##) Suppressing You can suppress false positives using one of the following mechanisms: * Adding the suppression attribute `tools:ignore="UselessLeaf"` on the problematic XML element (or one of its enclosing elements). You may also need to add the following namespace declaration on the root element in the XML file if it's not already there: `xmlns:tools="http://schemas.android.com/tools"`. ```xml <?xml version="1.0" encoding="UTF-8"?> <AbsoluteLayout xmlns:tools="http://schemas.android.com/tools" tools:ignore="UselessLeaf" ...> ... </AbsoluteLayout> ``` * Using a special `lint.xml` file in the source tree which turns off the check in that folder and any sub folder. A simple file might look like this: ```xml <?xml version="1.0" encoding="UTF-8"?> <lint> <issue id="UselessLeaf" severity="ignore" /> </lint> ``` Instead of `ignore` you can also change the severity here, for example from `error` to `warning`. You can find additional documentation on how to filter issues by path, regular expression and so on [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html). * In Gradle projects, using the DSL syntax to configure lint. For example, you can use something like ```gradle lintOptions { disable 'UselessLeaf' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore UselessLeaf ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).