Displayer

An open source multi-platform app for digital signage

Introduction

The Displayer app shows your content, described in a JSON file, in an endless loop, without any intervention, on the device of your choice.

Some of its features are:

• Works on multiple platforms:
  • Android, including Android TV
  • Linux
  • Any other platform supported by Kotlin Multiplatform (KMP)
• Multiple regions
  • Center region to show your main content
  • Left and Bottom region to show secondary (scrolling) content
• Different types of content:
  • Text
  • Images
  • Clock
  • Live weather information (requires an OpenWeather API key)
  • Random content
• Locale-aware (for time formatting, temperature units,...)
• Is a launcher on Android platforms (including Android TV)

Displayer is being used successfully in the clubhouse of korfbalclub KCBJ to display information about upcoming events, sponsors, and live weather, without any intervention of the volunteer currently doing bar service.

Screenshots

Build and run

There are currently no binary builds available. You have to download/clone the source code and build the app to run it.

Building Displayer requires at minimum Java 17.

Optionally, you can open the project in IntelliJ IDEA (tested with version 2022.3.1 of the Community Edition running on Java 17)

Android

• Define sdk.dir in local.properties to point to your Android SDK location
• Execute ./gradlew assemble to build the Android app
• The resulting APK files will be placed in android/build/outputs/apk
• Use ADB to install the app on your Android device: adb install android/build/outputs/apk/debug/android-debug.apk

Desktop

• Execute ./gradlew package to build the desktop apps
• The resulting binaries will be placed in desktop/build/compose/binaries

Display file structure

There are sample display files available showcasing different features.

A detailed explanation of the display file structure is coming soon...

Send commands

Android

On Android, you'll need ADB to send commands to Displayer. Commands are sent to the app as Android intents with extras.

Load a display file

adb shell am start -a "android.intent.action.VIEW" -d "URL_OF_DISPLAY_FILE"

Replace URL_OF_DISPLAY_FILE with the URL of your own display file, e.g. https://example.com/displayer.json

Set OpenWeather API key

adb shell am start -a "com.displayer.action.CONFIG" -e EXTRA_OPEN_WEATHER_API_KEY YOUR_API_KEY

Replace YOUR_API_KEY with your own OpenWeather API key obtained from the OpenWeather API console.

Desktop

On desktop, you must start Displayer with extra parameters to enable the admin endpoint. This endpoint is needed to send commands to the app (using curl, wget or any web browser).

Example:

/opt/displayer/bin/Displayer --port=YOUR_PORT --secret=YOUR_SECRET

Replace YOUR_PORT with the TCP/IP port number to use for the admin endpoint.

Replace YOUR_PORT with a secret that must be included in any request to the admin port.

Load a display file

curl "http://YOUR_HOST:YOUR_PORT/config?secret=YOUR_SECRET&url=URL_OF_DISPLAY_FILE"

Replace URL_OF_DISPLAY_FILE with the URL of your own display file, e.g. https://example.com/displayer.json. Make sure you URL-encode all special characters in the URL.

Set OpenWeather API key

curl "http://YOUR_HOST:YOUR_PORT/config?secret=YOUR_SECRET&open-weather-api-key=YOUR_API_KEY"

Replace YOUR_API_KEY with your own OpenWeather API key obtained from the OpenWeather API console.

Android TV

After installing Displayer on Android TV, you can disable the original Android TV launcher. This will make sure that Displayer automatically starts after rebooting your Android TV device.

To disable the original Android TV launcher enter the following commands:

adb shell pm disable-user --user 0 com.google.android.tvlauncher
adb shell pm disable-user --user 0 com.google.android.tungsten.setupwraith

You can always re-enable the original Android TV launcher by entering the following commands:

adb shell pm enable com.google.android.tvlauncher
adb shell pm enable com.google.android.tungsten.setupwraith

Built with

• Kotlin Multiplatform
• Compose Desktop
• Kotlin Serialization
• Kotlin Date/Time
• Ktor: HTTP server
• Koin: dependency injection framework
• Kamel: asynchronous media loading library for Compose
• Kamel: Kotlin Multiplatform library to persist key-value data
• Kermit: Kotlin Multiplatform logging

License

Copyright 2022 Norio BV

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

   http://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.