Add the Android app: a WebView around public_html

A single Activity holding one WebView, in Java rather than Kotlin — for
~120 lines of setup Kotlin would only add its Gradle plugin, its stdlib
in the APK and a third version to keep aligned with Gradle and AGP. One
dependency: androidx.webkit 1.16.0.

The assets are served from https://appassets.androidplatform.net through
WebViewAssetLoader rather than file://. That is the part that matters: an
https origin is a secure context, and localStorage — which holds every
setting and the match in progress — is blocked on file://, so a saved
game would silently vanish. Confirmed on device: force-quit mid-match and
everything comes back.

public_html stays the only copy of the web app. A task syncs it into the
assets at build time, so the browser version and the app version cannot
drift; the APK's index.html hashes identical to the working tree. sw.js
is left out on purpose — it is cache-first, and a service-worker cache
outlives an app upgrade, so it would serve a stale index.html with no way
to clear it. The APK is the cache now.

Three web APIs don't exist in a WebView, so the Activity supplies them:
FLAG_KEEP_SCREEN_ON for navigator.wakeLock, native immersive mode for
requestFullscreen(), and LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES so the
panels' env(safe-area-inset-*) has something to report. textZoom is
pinned to 100: the layout is built on clamp() and vw, and a large system
font would scale the text inside it.

The manifest declares no permissions whatsoever.

Wiring note: AGP 9 refuses a Provider in sourceSets.assets.srcDir, since
it can't tell generated from static directories. The sync is a task with
a DirectoryProperty output, attached via androidComponents.onVariants,
which is the supported path and carries the task dependency.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
2026-08-11 19:10:38 +02:00
co-authored by Claude Opus 5
parent 6069ef270e
commit 9f2081a0c9
17 changed files with 653 additions and 0 deletions
+78
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import javax.inject.Inject
plugins {
id("com.android.application")
}
android {
namespace = "nl.hansdezwart.bgclock"
compileSdk = 36
buildToolsVersion = "36.0.0"
defaultConfig {
applicationId = "nl.hansdezwart.bgclock"
minSdk = 26
targetSdk = 36
versionCode = 1
versionName = "1.0"
}
compileOptions {
sourceCompatibility = JavaVersion.VERSION_17
targetCompatibility = JavaVersion.VERSION_17
}
buildTypes {
release {
isMinifyEnabled = false
}
}
}
/**
* The web app is not copied into the repo — it is read out of public_html at
* build time, so the browser version and the app version cannot drift.
*
* sw.js is left behind on purpose: it is cache-first, and a service-worker cache
* outlives an app upgrade, so it would go on serving the old index.html with no
* way to clear it. Without the file the registration fails into its own .catch,
* and the APK is the cache instead.
*/
abstract class SyncWebAssets : DefaultTask() {
@get:InputDirectory
@get:PathSensitive(PathSensitivity.RELATIVE)
abstract val source: DirectoryProperty
@get:OutputDirectory
abstract val outputDir: DirectoryProperty
@get:Inject
abstract val fs: FileSystemOperations
@TaskAction
fun run() {
fs.sync {
from(source) { exclude("sw.js") }
into(outputDir)
}
}
}
val webAssets = tasks.register<SyncWebAssets>("syncWebAssets") {
source.fileValue(rootProject.file("../public_html"))
}
// the Variant API, not sourceSets.assets.srcDir: AGP 9 refuses a Provider there
// because it can't tell generated from static, and this way the task dependency
// is carried automatically
androidComponents {
onVariants { variant ->
variant.sources.assets?.addGeneratedSourceDirectory(webAssets, SyncWebAssets::outputDir)
}
}
dependencies {
// the only dependency: WebViewAssetLoader, which serves the assets over a
// real https origin so they count as a secure context
implementation("androidx.webkit:webkit:1.16.0")
}
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<?xml version="1.0" encoding="utf-8"?>
<!-- This app declares no permissions at all, deliberately. The clock lives
entirely inside the APK and never makes a request, so it needs no INTERNET;
there are no haptics, so it needs no VIBRATE. Keep it that way: the empty
permission list is worth more than any feature that would spend it. -->
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:roundIcon="@mipmap/ic_launcher_round"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/Theme.BgClock">
<activity
android:name=".MainActivity"
android:exported="true"
android:launchMode="singleTask"
android:screenOrientation="portrait"
android:resizeableActivity="false"
android:windowSoftInputMode="stateAlwaysHidden"
android:configChanges="orientation|screenSize|screenLayout|smallestScreenSize|keyboardHidden|uiMode|density|fontScale|navigation|touchscreen">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
@@ -0,0 +1,141 @@
package nl.hansdezwart.bgclock;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.view.WindowInsets;
import android.view.WindowInsetsController;
import android.view.WindowManager;
import android.webkit.WebResourceRequest;
import android.webkit.WebResourceResponse;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import androidx.webkit.WebViewAssetLoader;
/**
* The whole app: one WebView holding the clock from public_html.
*
* The assets are served over https://appassets.androidplatform.net rather than
* file:// because that is a secure context — localStorage, which holds every
* setting and the match in progress, is blocked on file:// and the saved game
* would silently vanish.
*/
public class MainActivity extends Activity {
private static final String ORIGIN = "https://appassets.androidplatform.net";
private static final int INK = 0xFF332E2B; // --bar, so there is no white flash
private WebView web;
@SuppressLint("SetJavaScriptEnabled")
@Override
protected void onCreate(Bundle savedState) {
super.onCreate(savedState);
// in a browser the page holds a screen wake lock; navigator.wakeLock
// does not exist in a WebView, so the window keeps the screen on. The
// page requests it unconditionally at boot, so always-on is parity.
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
// draw behind the cutout, so the CSS env(safe-area-inset-*) the panels
// already use has something to report
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
getWindow().getAttributes().layoutInDisplayCutoutMode =
WindowManager.LayoutParams.LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES;
}
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
getWindow().setDecorFitsSystemWindows(false);
}
final WebViewAssetLoader loader = new WebViewAssetLoader.Builder()
.addPathHandler("/assets/", new WebViewAssetLoader.AssetsPathHandler(this))
.build();
web = new WebView(this);
web.setBackgroundColor(INK);
web.setOverScrollMode(View.OVER_SCROLL_NEVER); // no rubber-band glow on a fixed page
web.setVerticalScrollBarEnabled(false);
web.setHorizontalScrollBarEnabled(false);
WebSettings s = web.getSettings();
s.setJavaScriptEnabled(true);
s.setDomStorageEnabled(true); // localStorage: settings and the live match
s.setMediaPlaybackRequiresUserGesture(false); // the Web Audio tick after a resume
s.setSupportZoom(false);
s.setBuiltInZoomControls(false);
// the layout is built on clamp() and vw; a large system font setting
// would scale the text inside it and break the two big readouts
s.setTextZoom(100);
web.setWebViewClient(new WebViewClient() {
@Override
public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) {
return loader.shouldInterceptRequest(request.getUrl());
}
@Override
public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
// the clock has no outbound links and no network permission;
// refuse anything that isn't our own assets, whatever happens
return !request.getUrl().toString().startsWith(ORIGIN);
}
});
setContentView(web);
web.loadUrl(ORIGIN + "/assets/index.html");
}
@Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
if (hasFocus) hideSystemBars();
}
/** The page calls requestFullscreen(), which a WebView ignores. This is that. */
private void hideSystemBars() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
WindowInsetsController c = getWindow().getInsetsController();
if (c != null) {
c.hide(WindowInsets.Type.systemBars());
c.setSystemBarsBehavior(
WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE);
}
} else {
getWindow().getDecorView().setSystemUiVisibility(
View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
}
}
// forwarded so the page's visibilitychange fires — that is what calls
// saveGame() and nudges the audio context back after backgrounding
@Override
protected void onPause() {
super.onPause();
if (web != null) web.onPause();
}
@Override
protected void onResume() {
super.onResume();
if (web != null) web.onResume();
}
@Override
protected void onDestroy() {
if (web != null) {
setContentView(new View(this)); // detach before destroying
web.destroy();
web = null;
}
super.onDestroy();
}
}
@@ -0,0 +1,10 @@
<?xml version="1.0" encoding="utf-8"?>
<!-- Generated from public_html/icon-maskable-512.png. That icon is drawn for the
web maskable safe zone (the middle 80%); an adaptive icon only guarantees the
middle 66.7%. Scaling the art to 360 on a 432 canvas (0.667/0.80) lands its
safe circle exactly on Android's, so no mask shape can clip it. -->
<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
<background android:drawable="@color/ink" />
<foreground android:drawable="@mipmap/ic_launcher_foreground" />
<monochrome android:drawable="@mipmap/ic_launcher_foreground" />
</adaptive-icon>
@@ -0,0 +1,6 @@
<?xml version="1.0" encoding="utf-8"?>
<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
<background android:drawable="@color/ink" />
<foreground android:drawable="@mipmap/ic_launcher_foreground" />
<monochrome android:drawable="@mipmap/ic_launcher_foreground" />
</adaptive-icon>
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<?xml version="1.0" encoding="utf-8"?>
<resources>
<!-- the CSS var named bar in index.html: the control bar, and the colour
behind the launcher icon -->
<color name="ink">#332E2B</color>
</resources>
@@ -0,0 +1,5 @@
<?xml version="1.0" encoding="utf-8"?>
<resources>
<!-- matches short_name in manifest.webmanifest -->
<string name="app_name">BG Clock</string>
</resources>
@@ -0,0 +1,11 @@
<?xml version="1.0" encoding="utf-8"?>
<resources>
<!-- the platform Material theme, so the app needs no appcompat -->
<style name="Theme.BgClock" parent="@android:style/Theme.Material.NoActionBar">
<!-- the window is this colour before the WebView paints, so the launch
never flashes white -->
<item name="android:windowBackground">@color/ink</item>
<item name="android:statusBarColor">@android:color/transparent</item>
<item name="android:navigationBarColor">@android:color/transparent</item>
</style>
</resources>
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plugins {
id("com.android.application") version "9.3.1" apply false
}
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org.gradle.jvmargs=-Xmx2g -Dfile.encoding=UTF-8
android.useAndroidX=true
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distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-9.7.0-bin.zip
networkTimeout=10000
retries=0
retryBackOffMs=500
validateDistributionUrl=true
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
Vendored Executable
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#!/bin/sh
#
# Copyright © 2015 the original authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# SPDX-License-Identifier: Apache-2.0
#
##############################################################################
#
# gradlew start up script for POSIX generated by Gradle.
#
# Important for running:
#
# (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
# noncompliant, but you have some other compliant shell such as ksh or
# bash, then to run this script, type that shell name before the whole
# command line, like:
#
# ksh gradlew
#
# Busybox and similar reduced shells will NOT work, because this script
# requires all of these POSIX shell features:
# * functions;
# * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
# «${var#prefix}», «${var%suffix}», and «$( cmd )»;
# * compound commands having a testable exit status, especially «case»;
# * various built-in commands including «command», «set», and «ulimit».
#
# Important for patching:
#
# (2) This script targets any POSIX shell, so it avoids extensions provided
# by Bash, Ksh, etc; in particular arrays are avoided.
#
# The "traditional" practice of packing multiple parameters into a
# space-separated string is a well documented source of bugs and security
# problems, so this is (mostly) avoided, by progressively accumulating
# options in "$@", and eventually passing that to Java.
#
# Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
# and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
# see the in-line comments for details.
#
# There are tweaks for specific operating systems such as AIX, CygWin,
# Darwin, MinGW, and NonStop.
#
# (3) This script is generated from the Groovy template
# https://github.com/gradle/gradle/blob/3d91ce3b8caaf77ad09f381f43615b715b53f72c/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
# within the Gradle project.
#
# You can find Gradle at https://github.com/gradle/gradle/.
#
##############################################################################
# Attempt to set APP_HOME
# Resolve links: $0 may be a link
app_path=$0
# Need this for daisy-chained symlinks.
while
APP_HOME=${app_path%"${app_path##*/}"} # leaves a trailing /; empty if no leading path
[ -h "$app_path" ]
do
ls=$( ls -ld "$app_path" )
link=${ls#*' -> '}
case $link in #(
/*) app_path=$link ;; #(
*) app_path=$APP_HOME$link ;;
esac
done
# This is normally unused
# shellcheck disable=SC2034
APP_BASE_NAME=${0##*/}
# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s\n' "$PWD" ) || exit
# Use the maximum available, or set MAX_FD != -1 to use that value.
MAX_FD=maximum
warn () {
echo "$*"
} >&2
die () {
echo
echo "$*"
echo
exit 1
} >&2
# OS specific support (must be 'true' or 'false').
cygwin=false
msys=false
darwin=false
nonstop=false
case "$( uname )" in #(
CYGWIN* ) cygwin=true ;; #(
Darwin* ) darwin=true ;; #(
MSYS* | MINGW* ) msys=true ;; #(
NONSTOP* ) nonstop=true ;;
esac
# Determine the Java command to use to start the JVM.
if [ -n "$JAVA_HOME" ] ; then
if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
# IBM's JDK on AIX uses strange locations for the executables
JAVACMD=$JAVA_HOME/jre/sh/java
else
JAVACMD=$JAVA_HOME/bin/java
fi
if [ ! -x "$JAVACMD" ] ; then
die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi
else
JAVACMD=java
if ! command -v java >/dev/null 2>&1
then
die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi
fi
# Increase the maximum file descriptors if we can.
if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
case $MAX_FD in #(
max*)
# In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
# shellcheck disable=SC2039,SC3045
MAX_FD=$( ulimit -H -n ) ||
warn "Could not query maximum file descriptor limit"
esac
case $MAX_FD in #(
'' | soft) :;; #(
*)
# In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
# shellcheck disable=SC2039,SC3045
ulimit -n "$MAX_FD" ||
warn "Could not set maximum file descriptor limit to $MAX_FD"
esac
fi
# Collect all arguments for the java command, stacking in reverse order:
# * args from the command line
# * the main class name
# * -classpath
# * -D...appname settings
# * --module-path (only if needed)
# * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
# For Cygwin or MSYS, switch paths to Windows format before running java
if "$cygwin" || "$msys" ; then
APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
JAVACMD=$( cygpath --unix "$JAVACMD" )
# Now convert the arguments - kludge to limit ourselves to /bin/sh
for arg do
if
case $arg in #(
-*) false ;; # don't mess with options #(
/?*) t=${arg#/} t=/${t%%/*} # looks like a POSIX filepath
[ -e "$t" ] ;; #(
*) false ;;
esac
then
arg=$( cygpath --path --ignore --mixed "$arg" )
fi
# Roll the args list around exactly as many times as the number of
# args, so each arg winds up back in the position where it started, but
# possibly modified.
#
# NB: a `for` loop captures its iteration list before it begins, so
# changing the positional parameters here affects neither the number of
# iterations, nor the values presented in `arg`.
shift # remove old arg
set -- "$@" "$arg" # push replacement arg
done
fi
# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
# Collect all arguments for the java command:
# * DEFAULT_JVM_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
# and any embedded shellness will be escaped.
# * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
# treated as '${Hostname}' itself on the command line.
set -- \
"-Dorg.gradle.appname=$APP_BASE_NAME" \
-jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
"$@"
# Stop when "xargs" is not available.
if ! command -v xargs >/dev/null 2>&1
then
die "xargs is not available"
fi
# Use "xargs" to parse quoted args.
#
# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
#
# In Bash we could simply go:
#
# readarray ARGS < <( xargs -n1 <<<"$var" ) &&
# set -- "${ARGS[@]}" "$@"
#
# but POSIX shell has neither arrays nor command substitution, so instead we
# post-process each arg (as a line of input to sed) to backslash-escape any
# character that might be a shell metacharacter, then use eval to reverse
# that process (while maintaining the separation between arguments), and wrap
# the whole thing up as a single "set" statement.
#
# This will of course break if any of these variables contains a newline or
# an unmatched quote.
#
eval "set -- $(
printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
xargs -n1 |
sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
tr '\n' ' '
)" '"$@"'
exec "$JAVACMD" "$@"
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@rem
@rem Copyright 2015 the original author or authors.
@rem
@rem Licensed under the Apache License, Version 2.0 (the "License");
@rem you may not use this file except in compliance with the License.
@rem You may obtain a copy of the License at
@rem
@rem https://www.apache.org/licenses/LICENSE-2.0
@rem
@rem Unless required by applicable law or agreed to in writing, software
@rem distributed under the License is distributed on an "AS IS" BASIS,
@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@rem See the License for the specific language governing permissions and
@rem limitations under the License.
@rem
@rem SPDX-License-Identifier: Apache-2.0
@rem
@if "%DEBUG%"=="" @echo off
@rem ##########################################################################
@rem
@rem gradlew startup script for Windows
@rem
@rem ##########################################################################
@rem Set local scope for the variables, and ensure extensions are enabled
setlocal EnableExtensions
set DIRNAME=%~dp0
if "%DIRNAME%"=="" set DIRNAME=.
@rem This is normally unused
set APP_BASE_NAME=%~n0
set APP_HOME=%DIRNAME%
@rem Resolve any "." and ".." in APP_HOME to make it shorter.
for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
@rem Find java.exe
if defined JAVA_HOME goto findJavaFromJavaHome
set JAVA_EXE=java.exe
%JAVA_EXE% -version >NUL 2>&1
if %ERRORLEVEL% equ 0 goto execute
echo. 1>&2
echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
echo. 1>&2
echo Please set the JAVA_HOME variable in your environment to match the 1>&2
echo location of your Java installation. 1>&2
"%COMSPEC%" /c exit 1
:findJavaFromJavaHome
set JAVA_HOME=%JAVA_HOME:"=%
set JAVA_EXE=%JAVA_HOME%/bin/java.exe
if exist "%JAVA_EXE%" goto execute
echo. 1>&2
echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
echo. 1>&2
echo Please set the JAVA_HOME variable in your environment to match the 1>&2
echo location of your Java installation. 1>&2
"%COMSPEC%" /c exit 1
:execute
@rem Setup the command line
@rem Execute gradlew
@rem endlocal doesn't take effect until after the line is parsed and variables are expanded
@rem which allows us to clear the local environment before executing the java command
endlocal & "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %* & call :exitWithErrorLevel
:exitWithErrorLevel
@rem Use "%COMSPEC%" /c exit to allow operators to work properly in scripts
"%COMSPEC%" /c exit %ERRORLEVEL%
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pluginManagement {
repositories {
google()
mavenCentral()
gradlePluginPortal()
}
}
dependencyResolutionManagement {
repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
repositories {
google()
mavenCentral()
}
}
rootProject.name = "bgclock"
include(":app")