CustomLintRules Android Arsenal

A basic, Gradle-based project template for writing custom Android Lint rules.

If you want to learn more about custom Lint rules please check this reference guide. If you are still looking for more details you are welcome to check this workshop on custom Lint rules.

Getting started

Step 1

Clone this repository and open it in the IDE of your choice.

git clone https://github.com/a11n/CustomLintRules.git

Step 2

In order to write your own custom Lint rules create a new class and make it extend Detector. See HelloWorldDetector for reference.

Depending on your use case you might also want to implement one of or more of Detector's interfaces:

  • JavaScanner: Specialized interface for detectors that scan Java source file parse trees
  • XmlScanner: Specialized interface for detectors that scan XML files
  • ResourceFolderScanner: Specialized interface for detectors that scan resource folders
  • ...

I recommend to have a look at the default set of detectors to get an impression of the anatomy of Detectors. [1]

Step 3

Detectors scan the development artifacts for one or more issues to report. Last but not least you need to register your custom issue(s) in the CustomIssueRegistry.

Step 4

Finally you might want to have a unit test for your custom Lint rules in place. Since end of July 2015 there is an official lint-tests library available for that purpose. [2]. HelloWorldDetectorTest demonstrates how to test custom Lint rules.

That’s it.

Application

In order to apply your custom Lint rules to your project you basically have two options.

1. Copy your rules to a specific folder

By default, Lint will look for custom Lint rules in ~/.android/lint and will consider them during analysis. To apply your custom Lint rules just assemble your rules and copy the resulting *.jar to that folder:

./gradlew clean assemble

On Unix based systems you can simply use ./buildAndInstall for your convenience.

2. Wrap your rules into an AAR bundle

A more advanced option is the new AAR format, which allows to bundle custom Lint rules [3]. You can include the resulting *.aar file into your Android application project. When executing ./gradlew lint in your Android application project your custom Lint rules will be considered automatically.

To wrap your custom Lint rules into an AAR container just execute:

./gradlew aarWrapper:assemble

You will find the AAR file in aarWrapper/build/outputs/aar/. Just copy it to the libs folder of your Android application project.

Remark

As Google points out very significant, the Lint API is not final and may change in future releases [4].

This project refers to the most recent (July 2015), stable version (24.3.0) of the Lint API [5].

Credits

Approaches used in this project have (partly) been adopted from this blog post [6]. Thank you Cheng Yang for sharing your ideas and findings.

References

  1. https://android.googlesource.com/platform/tools/base/+/master/lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks (visited 2015-04-25)
  2. https://bintray.com/android/android-tools/com.android.tools.lint.lint-tests/24.3.0/view (visited 2015-08-01)
  3. http://tools.android.com/tech-docs/new-build-system/aar-format (visited 2015-04-25)
  4. http://tools.android.com/tips/lint/writing-a-lint-check (visited 2015-04-25)
  5. https://bintray.com/android/android-tools/com.android.tools.lint.lint-api/24.3.0/view (visited 2015-08-01)
  6. https://engineering.linkedin.com/android/writing-custom-lint-checks-gradle (visited 2015-04-25)
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