Properly configure checkstyle for Android modules

dont-kill-me-lib/build.gradle

 plugins {
     id 'com.android.library'
+    id 'checkstyle' // only needed for Java code
 }
 
 android {
@@ -27,3 +28,5 @@ android {
 dependencies {
     implementation "androidx.annotation:annotation:1.3.0"
 }
+
+apply from: "${rootProject.rootDir}/gradle/checkstyle.gradle"

gradle/checkstyle.gradle

+task checkstyleMain(type: Checkstyle) {
+    source 'src/main/java'
+    include '**/*.java'
+    classpath = files()
+    reports {
+        xml {
+            destination file("build/reports/checkstyle/main.xml")
+        }
+        html {
+            destination file("build/reports/checkstyle/main.html")
+        }
+    }
+    check.dependsOn it
+}
+
+task checkstyleTest(type: Checkstyle) {
+    source 'src/test/java'
+    include '**/*.java'
+    classpath = files()
+    reports {
+        xml {
+            destination file("build/reports/checkstyle/test.xml")
+        }
+        html {
+            destination file("build/reports/checkstyle/test.html")
+        }
+    }
+    check.dependsOn it
+}

mailbox-android/build.gradle

@@ -152,3 +152,4 @@ tasks.withType(MergeResources) {
 }
 
 apply from: "${rootProject.rootDir}/gradle/ktlint.gradle"
+apply from: "${rootProject.rootDir}/gradle/checkstyle.gradle"