(#) Back button !!! WARNING: Back button This is a warning. Id : `BackButton` Summary : Back button Note : **This issue is disabled by default**; use `--enable BackButton` Severity : Warning Category : Usability 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 See : https://d.android.com/r/studio-ui/designer/material/design 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/ButtonDetector.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/ButtonDetectorTest.java) Copyright Year : 2012 According to the Android Design Guide, "Other platforms use an explicit back button with label to allow the user to navigate up the application's hierarchy. Instead, Android uses the main action bar's app icon for hierarchical navigation and the navigation bar's back button for temporal navigation." This check is not very sophisticated (it just looks for buttons with the label "Back"), so it is disabled by default to not trigger on common scenarios like pairs of Back/Next buttons to paginate through screens. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text res/layout/buttonbar.xml:183:Warning: Back buttons are not standard on Android; see design guide's navigation section [BackButton] <Button ------ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here are the relevant source files: `res/layout/buttonbar.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" > <!-- Hardcoded strings, wrong order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="OK" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Cancel" /> </LinearLayout> <!-- Hardcoded strings, right order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Cancel" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="OK" /> </LinearLayout> <!-- @android:string resources, wrong order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@android:string/ok" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@android:string/cancel" /> </LinearLayout> <!-- @android:string resources, right order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@android:string/cancel" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@android:string/ok" /> </LinearLayout> <!-- @string/ok/cancel resources, right order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/cancel" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/ok" /> </LinearLayout> <!-- @string/ok/cancel resources, wrong order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/ok" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/cancel" /> </LinearLayout> <!-- Random name resources, right order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/giveup" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/resume" /> </LinearLayout> <!-- Random name resources, wrong order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/resume" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/giveup" /> </LinearLayout> <!-- Random name resources with varying case, wrong order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/resume2" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/giveup2" /> </LinearLayout> <!-- Resources with only one of OK and Cancel, wrong order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/ok" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/abort" /> </LinearLayout> <!-- Resources with only one of OK and Cancel, wrong order --> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" > <Button android:layout_width="wrap_content" android:background="?android:attr/selectableItemBackground" android:layout_height="wrap_content" android:text="@string/send" /> <Button android:layout_width="wrap_content" android:background="?android:attr/selectableItemBackground" android:layout_height="wrap_content" android:text="@string/cancel" /> </LinearLayout> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/goback" /> </LinearLayout> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ `res/values/buttonbar-values.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <?xml version="1.0" encoding="utf-8"?> <resources> <string name="button"> Button </string> <string name="ok"> OK </string> <string name="cancel"> Cancel </string> <string name="resume"> OK </string> <string name="giveup"> Cancel </string> <string name="resume2"> Ok </string> <string name="giveup2">"CANCEL"</string> <string name="send"> Send </string> <string name="abort">Abort</string> <string name="goback">'Back'</string> </resources> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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/ButtonDetectorTest.java) 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, `ButtonDetector.testBack`. 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="BackButton"` 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"?> <resources xmlns:tools="http://schemas.android.com/tools"> ... <Button tools:ignore="BackButton" .../> ... </resources> ``` * 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="BackButton" 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 'BackButton' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore BackButton ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).