Files
simplex-chat/apps/multiplatform
Narasimha-sc 58aee54ad6 android, desktop, ios: do not offer to accept or join twice
An invitation being accepted is a fact about the invitation, not about the
view that shows it, but each view kept its own flag. The chat list row, the
long-press menu, the accept alert, the composer banner, the chat item
"tap to join" and the notification action therefore disagreed: accepting
from one left the others fully enabled, and the second accept reached the
core with an invitation the first one had already used.

ChatModel now records which contact requests are being accepted and which
groups are being joined. The shared acceptContactRequest and the new
joinGroup maintain it, so every caller participates without changing its
call site, and every view derives from it instead of owning a flag. The
record is taken before the request is sent, so a second tap in the same
view is blocked as well.

The connect composer no longer renders in a group's support scope: on
desktop that is a second view of the same group next to the main one, and
it offered its own Join button.
2026-08-20 11:43:11 +00:00
..
2023-06-29 12:53:11 +01:00
2026-01-24 17:59:46 +00:00

Android App Development

This is a guide to contributing to the develop of the SimpleX android and desktop apps.

Project Overview

This is the Kotlin Multiplatform (KMP) mobile and desktop client for SimpleX Chat, sharing code between Android and Desktop (JVM) platforms using Compose Multiplatform for UI.

Build Commands

# Android debug APK
./gradlew assembleDebug

# Android release APK
./gradlew assembleRelease

# Desktop distribution (current OS)
./gradlew :desktop:packageDistributionForCurrentOS

# Run desktop/JVM tests
./gradlew desktopTest

# Run Android instrumented tests (requires connected device/emulator)
./gradlew connectedAndroidTest

# Build native libraries for all platforms
./gradlew common:cmakeBuild -PcrossCompile

# Clean build
./gradlew clean

Architecture

Module Structure

  • common/ - Shared code (Compose UI, models, business logic)
    • src/commonMain/ - Cross-platform code
    • src/androidMain/ - Android-specific implementations
    • src/desktopMain/ - Desktop-specific implementations
  • android/ - Android app container
  • desktop/ - Desktop JVM app container

Key Components (common/src/commonMain/kotlin/chat/simplex/common/)

  • model/ChatModel.kt - Main state container with reactive properties (MutableState, MutableStateFlow)
  • model/SimpleXAPI.kt - API bindings to Haskell core library via FFI
  • platform/Core.kt - FFI interface to native libapp library
  • platform/ - Platform abstraction layer (expect/actual pattern for Android/Desktop specifics)
  • views/ - Compose UI screens organized by feature (chat, chatlist, call, usersettings, etc.)
  • ui/theme/ - Design system (colors, typography, shapes)

Native Integration

The app calls into a Haskell core library via JNI/FFI:

  • CMake builds in common/src/commonMain/cpp/android/ and cpp/desktop/
  • Cross-compilation toolchains in cpp/toolchains/
  • Built libraries go to cpp/desktop/libs/ (organized by platform)

Configuration

local.properties (create from local.properties.example)

compression.level=0          # APK compression (0-9)
enable_debuggable=true       # Debug mode
application_id.suffix=.debug # Multiple app instances on same device
app.name=SimpleX Debug       # App name for debug builds

gradle.properties

Contains versions (Kotlin, Compose, AGP) and app version info. Key settings:

  • kotlin.jvm.target=11
  • database.backend=sqlite (or postgres)

Testing

Tests are in:

  • common/src/commonTest/kotlin/ - Cross-platform tests
  • common/src/desktopTest/kotlin/ - Desktop-specific tests (run with ./gradlew desktopTest)
  • android/src/androidTest/ - Android instrumented tests

Resources & Localization

  • String resources: common/src/commonMain/resources/MR/base/strings.xml + 21 language variants
  • Uses Moko Resources (dev.icerock.moko:resources) for cross-platform resource management
  • The adjustFormatting gradle task validates string resources during build

Platform-Specific Notes

Android

  • Min SDK 26, Target SDK 35
  • NDK 23.1.7779620
  • Supports ABI splits: arm64-v8a, armeabi-v7a
  • Deep linking requires SHA certificate fingerprint in assetlinks.json (see README.md)

Desktop

  • Distributions: DMG (macOS), MSI/EXE (Windows), DEB (Linux)
  • Mac signing/notarization configured via local.properties
  • Video playback uses VLCJ

Gotchas

In order for the SimpleX app to be automatically adopted for opening links from https://simplex.chat the SHA certificate fingerprint for the App installed on the phone must be in the hosted assetlinks.json file on simplex.chat.

The accepted fingerprints are in the sha256_cert_fingerprints list.

To find your SHA certificate fingerprint perform the following steps.

  1. Build and install your development version of the app as usual
  2. From the terminal in Android studio run adb shell pm get-app-links chat.simplex.app
  3. Copy the signature listed in signatures in the result
  4. Add your signature to assetlinks.json in the website repo and make a PR. On approval, wait a few minutes for the changes to propagate to the public website and then you should be able to verify SimpleX.

More information is available here. If there is no response when running the pm get-app-links command, the intents in AndroidManifest.xml are likely misspecified. A verification attempt can be triggered using adb shell pm verify-app-links --re-verify chat.simplex.app.

Note that this is not an issue for the app store build of the app as this is signed with our app store credentials and thus there is a stable signature over users. Developers do not have general access to these credentials for development and testing.

Adding icons

  1. Find a Material symbol in Rounded category.

  2. Set weight to 400, grade to -25 and size to 48px.

  3. Click on the icon, choose Android and download XML file.

  4. Update the color to black (#FF000000) and the size to "24.dp", as in other icons.

For example, this is add reaction icon.