(#) Memory allocations within drawing code !!! WARNING: Memory allocations within drawing code This is a warning. Id : `DrawAllocation` Summary : Memory allocations within drawing code Severity : Warning Category : Performance Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : Initial 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/JavaPerformanceDetector.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/JavaPerformanceDetectorTest.java) Copyright Year : 2012 You should avoid allocating objects during a drawing or layout operation. These are called frequently, so a smooth UI can be interrupted by garbage collection pauses caused by the object allocations. The way this is generally handled is to allocate the needed objects up front and to reuse them for each drawing operation. Some methods allocate memory on your behalf (such as `Bitmap.create`), and these should be handled in the same way. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/test/pkg/MyView.java:18:Warning: Avoid object allocations during draw/layout operations (preallocate and reuse instead) [DrawAllocation] bitmap = Bitmap.createBitmap(100, 100, null); ----------------------------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `src/test/pkg/MyView.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package test.pkg; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Canvas; import android.util.AttributeSet; import android.view.View; public abstract class MyView extends View { public MyView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); bitmap = Bitmap.createBitmap(100, 100, null); } private Bitmap bitmap; } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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/JavaPerformanceDetectorTest.java) for the unit tests for this check to see additional scenarios. (##) 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("DrawAllocation") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("DrawAllocation") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection DrawAllocation 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="DrawAllocation" 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 'DrawAllocation' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore DrawAllocation ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).