OrientDemo

A small Mob app that demonstrates the device screen-orientation API: reading the current orientation, subscribing to rotation changes, and locking or unlocking the app to a specific orientation. The same Elixir UI runs on both iOS and Android, with the BEAM on the device.

Generated with mix mob.new (mob_new 0.4.14) and built against mob ~> 0.7.7.

What it shows

lib/orient_demo/orientation_screen.ex exercises Mob.Device:

Mob.Device.orientation()
# :portrait | :portrait_upside_down | :landscape_left | :landscape_right | :unknown

Mob.Device.subscribe(:display)
# screen process then receives {:mob_device, :orientation_changed, orientation}

Mob.Device.lock_orientation(:landscape)
# force landscape (either side); also :portrait, :landscape_left, :landscape_right,
# :portrait_upside_down. Returns {:error, :invalid} for anything else.

Mob.Device.unlock_orientation()
# follow the sensor again

The screen shows the live orientation (kept current via the :display subscription) plus a button per lock value and an unlock button. Locking rotates the device and holds it there regardless of the OS auto-rotate setting.

Running it

Prerequisites: the Mob toolchain (Elixir/OTP from the pinned .tool-versions, Android SDK + JDK 17 for Android, Xcode for iOS). See the Mob getting-started guide.

mix deps.get
mix mob.install            # first-run setup: OTP runtimes, icons, local.properties

# Android device or emulator (serial from `adb devices`):
mix mob.deploy --native --device <serial>

# iOS simulator (UDID from `mix mob.devices`):
mix mob.deploy --native --device <sim-udid>

# iOS physical device: one-time provisioning, then deploy:
mix mob.provision
mix mob.deploy --native --device <iphone-udid>

Open the app and tap Orientation.

How orientation lock works

lock_orientation/1 lives in Mob.Device (core Mob), but actually holding a rotation needs a little native glue in the app shell. mix mob.new (0.4.14+) scaffolds it automatically:

• iOS (ios/AppDelegate.m, ios/Info.plist): the app delegate returns mob_locked_orientation_mask() from application:supportedInterfaceOrientationsForWindow: (the window-level override that holds the lock over the root view controller), and the plist declares the landscape orientations so iOS will rotate to them.
• Android (MobBridge.kt, MainActivity.kt, beam_jni.c): MobBridge.orientationLock/1 calls Activity.setRequestedOrientation, and onConfigurationChanged forwards each rotation back to the BEAM (mob_send_orientation_changed) so orientation/0 and the :display subscription stay accurate.

Notes

This is a reference / demo app. mob.exs and android/local.properties are machine-local and gitignored; mix mob.install regenerates them. iOS signing config (team, profile) comes from mix mob.provision.