Android custom lint check use WebP format instead of PNG

Question

In the Android project. How to create a custom Detector that reports issues of using PNG format.

I have implemented a PngDetector but it does not work

class PngDetector : Detector(), Detector.XmlScanner {
    override fun getApplicableElements(): Collection<String>? =
        listOf("bitmap")

    override fun visitElement(context: XmlContext, element: Element) {
        val srcAttribute = element.getAttribute("src")
        if (srcAttribute.endsWith(".png")) {
            context.report(
                PNG_ISSUE,
                element,
                context.getLocation(element),
                "Use WebP format instead of PNG for bitmap resources"
            )
        }
    }
}

val PNG_ISSUE = Issue.create(
    id = "UseWebPInsteadOfPng",
    briefDescription = "Use WebP format instead of PNG",
    explanation = "WebP provides better compression and smaller file sizes compared to PNG.",
    category = Category.CORRECTNESS,
    priority = 5,
    severity = Severity.WARNING,
    implementation = Implementation(
        PngDetector::class.java,
        Scope.ALL_RESOURCES_SCOPE
    )
)

My code is:

<ImageView
            android:src="@drawable/wolf"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

The wolf image is png format but PngDetector can not detect