(#) Attribute unused on older versions !!! WARNING: Attribute unused on older versions This is a warning. Id : `UnusedAttribute` Summary : Attribute unused on older versions Severity : Warning Category : Correctness Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : Initial Affects : Resource files and resource folders 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/ApiDetector.kt) 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/ApiDetectorTest.java) Copyright Year : 2012 This check finds attributes set in XML files that were introduced in a version newer than the oldest version targeted by your application (with the `minSdkVersion` attribute). This is not an error; the application will simply ignore the attribute. However, if the attribute is important to the appearance or functionality of your application, you should consider finding an alternative way to achieve the same result with only available attributes, and then you can optionally create a copy of the layout in a layout-vNN folder which will be used on API NN or higher where you can take advantage of the newer attribute. Note: This check does not only apply to attributes. For example, some tags can be unused too, such as the new `` element in layouts introduced in API 21. !!! 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/linear.xml:11:Warning: Attribute android:theme is only used by tags in API level 23 and higher (current min is 21) [UnusedAttribute] android:theme="@android:style/Theme.Holo" /> ----------------------------------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here are the relevant source files: `src/AndroidManifest.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <manifest xmlns:android="http://schemas.android.com/apk/res/android"> <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="30" /> </manifest> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ `res/layout/linear.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <include layout="@layout/included" android:layout_width="wrap_content" android:layout_height="wrap_content" android:theme="@android:style/Theme.Holo" /> </LinearLayout> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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/ApiDetectorTest.java) for the unit tests for this check to see additional scenarios. (##) Suppressing You can suppress false positives using one of the following mechanisms: * Adding the suppression attribute `tools:ignore="UnusedAttribute"` 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"`. * 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="UnusedAttribute" 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 'UnusedAttribute' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore UnusedAttribute ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).