ci: check android code formatting

Signed-off-by: Michael Nahkies <michael@nahkies.co.nz>

.github/workflows/android.yml

@@ -35,3 +35,23 @@ jobs:
 
       - name: Run tests
         run: make test
+
+  fmt:
+    runs-on: ubuntu-latest
+
+    if: "!contains(github.event.head_commit.message, '[ci skip]')"
+
+    steps:
+      - name: Check out code
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - uses: actions/setup-go@0aaccfd150d50ccaeb58ebd88d36e91967a5f35b # v5.4.0
+        with:
+          go-version-file: "go.mod"
+      - name: Switch to Java 17 # Note: 17 is pre-installed on ubuntu-latest
+        uses: actions/setup-java@3a4f6e1af504cf6a31855fa899c6aa5355ba6c12 # v4.7.0
+        with:
+          distribution: "temurin"
+          java-version: "17"
+
+      - name: Run fmt-check
+        run: make fmt-check

Makefile

@@ -321,7 +321,8 @@ fmt: gradle-dependencies ## Format the Android code
 
 .PHONY: fmt-check
 fmt-check: gradle-dependencies ## Check the Android code is formatted
-	(cd android && ./gradlew ktfmtCheck)
+	(cd android && ./gradlew ktfmtCheck) \
+	|| (echo -e "\033[1;31mfmt-check failed. Run 'make fmt' to fix.\033[0m" && exit 1)
 
 .PHONY: emulator
 emulator: ## Start an android emulator instance

README.md

@@ -58,6 +58,9 @@ shell.
 The ktmft plugin on the default setting should be used to autoformat all Java, Kotlin
 and XML files in Android Studio.  Enable "Format on Save".
 
+This is checked in CI using `make fmt-check`, and you can also run reformat the files locally
+using: `make fmt`
+
 ### Docker
 
 If you wish to avoid installing software on your host system, a Docker based development strategy is available, you can build and start a shell with: