(#) Custom views in libraries should use res-auto-namespace !!! ERROR: Custom views in libraries should use res-auto-namespace This is an error, and is also enforced at build time when supported by the build system. For Android this means it will run during release builds. Id : `LibraryCustomView` Summary : Custom views in libraries should use res-auto-namespace Severity : Fatal Category : Correctness Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : Initial Affects : Manifest files and 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/NamespaceDetector.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/NamespaceDetectorTest.kt) Copyright Year : 2012 When using a custom view with custom attributes in a library project, the layout must use the special namespace http://schemas.android.com/apk/res-auto instead of a URI which includes the library project's own package. This will be used to automatically adjust the namespace of the attributes when the library resources are merged into the application project. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text res/layout/customview.xml:5:Error: When using a custom namespace attribute in a library project, use the namespace "http://schemas.android.com/apk/res-auto" instead [LibraryCustomView] xmlns:foo="http://schemas.android.com/apk/res/foo" -------------------------------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `res/layout/customview.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" xmlns:other="http://schemas.foo.bar.com/other" xmlns:foo="http://schemas.android.com/apk/res/foo" android:id="@+id/newlinear" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <foo.bar.Baz android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Button1" foo:misc="Custom attribute" tools:ignore="HardcodedText" > </foo.bar.Baz> <!-- Wrong namespace uri prefix: Don't warn --> <foo.bar.Baz android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Button1" other:misc="Custom attribute" tools:ignore="HardcodedText" > </foo.bar.Baz> </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/NamespaceDetectorTest.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, `NamespaceDetector.testCustom`. 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="LibraryCustomView"` 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="LibraryCustomView" 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 'LibraryCustomView' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore LibraryCustomView ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).