(#) Invalidating All RecyclerView Data !!! WARNING: Invalidating All RecyclerView Data This is a warning. Id : `NotifyDataSetChanged` Summary : Invalidating All RecyclerView Data Severity : Warning Category : Performance Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Affects : Kotlin and Java 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/RecyclerViewDetector.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/RecyclerViewDetectorTest.kt) Copyright Year : 2015 The `RecyclerView` adapter's `onNotifyDataSetChanged` method does not specify what about the data set has changed, forcing any observers to assume that all existing items and structure may no longer be valid. `LayoutManager`s will be forced to fully rebind and relayout all visible views. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/test/pkg/RecyclerViewTest.java:24:Warning: It will always be more efficient to use more specific change events if you can. Rely on notifyDataSetChanged as a last resort. [NotifyDataSetChanged] notifyDataSetChanged(); ---------------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/test/pkg/RecyclerViewTest.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package test.pkg; import androidx.recyclerview.widget.RecyclerView; import android.view.View; import android.widget.TextView; import java.util.List; @SuppressWarnings({"ClassNameDiffersFromFileName", "unused"}) public class RecyclerViewTest { // From https://developer.android.com/training/material/lists-cards.html public abstract static class Test1 extends RecyclerView.Adapter { private String[] mDataset; public static class ViewHolder extends RecyclerView.ViewHolder { public TextView mTextView; public ViewHolder(TextView v) { super(v); mTextView = v; } } public Test1(String[] myDataset) { mDataset = myDataset; notifyDataSetChanged(); } @Override public void onBindViewHolder(ViewHolder holder, int position) { } } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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/RecyclerViewDetectorTest.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, `RecyclerViewDetector.testClearAllData`. 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: * Using a suppression annotation like this on the enclosing element: ```kt // Kotlin @Suppress("NotifyDataSetChanged") fun method() { notifyDataSetChanged(...) } ``` or ```java // Java @SuppressWarnings("NotifyDataSetChanged") void method() { notifyDataSetChanged(...); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection NotifyDataSetChanged problematicStatement() ``` * 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="NotifyDataSetChanged" 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 'NotifyDataSetChanged' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore NotifyDataSetChanged ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).