Android: Custom Commands

Overview

On a CUSTOMAPP session with the same CXRLink instance, build payloads with Caps and send via sendCustomCmd, receiving replies in ICustomCmdCbk. Enables bidirectional binary messaging between the phone app and the glasses-side custom app.

CustomView sessions do not support custom commands.

Bidirectional channels

Must match glasses CXRServiceBridge and RenewCXRLSample CustomCmdViewModel:

Sample Caps fields (demo)

Phone → glasses (sendCustomCmd payload):

Caps().apply {
    write(“rk_custom_key”)
    write(“from client click times = $count”)
}

Glasses → phone (sendMessage payload):

Caps().apply {
    write(“message”)
    write(str)
}

Prerequisites

• Session type is CUSTOMAPP.
• Global CXRLink connected.
• Scene building completed: target app running on glasses.
• Link ready (CXR + Bluetooth).

Core APIs (phone)

ICustomCmdCbk

fun onCustomCmdResult(key: String?, payload: ByteArray?)

Parse with Caps.fromBytes(payload) following the agreed field order.

Caps example (phone)

link.sendCustomCmd(“rk_custom_client”, Caps().apply {
    write(“rk_custom_key”)
    write(“message from phone”)
})

link.setCXRCustomCmdCbk(object : ICustomCmdCbk {
    override fun onCustomCmdResult(key: String?, payload: ByteArray?) {
        if (key == “rk_custom_key” && payload != null) {
            val caps = Caps.fromBytes(payload)
        }
    }
})

Agree with the glasses app on channel keys, field order, types, and max packet size.

Constraints

• Send only when scene is ready and link is up.
• Clear Cmd callback on page destroy.
• Reuse the same CXRLink from CustomApp session creation.

Glasses-side: CXRServiceBridge

After CUSTOMAPP session build, the glasses app subscribes to phone command channels and replies via sendMessage.

Prerequisites

• Phone appStart succeeded (onOpenAppResult(true)).
• Glasses MainViewModel (or equivalent) has called subscribe on the agreed channel.

Core APIs

StatusListener (excerpt)

MsgCallback

fun onReceive(name: String?, args: Caps?, bytes: ByteArray?)

Integration example (glasses)

class MainViewModel : ViewModel() {
    private val cxrBridge = CXRServiceBridge()
    private val clientKey = “rk_custom_client”
    private val cmdKey = “rk_custom_key”

    private val msgCallback = object : CXRServiceBridge.MsgCallback {
        override fun onReceive(name: String?, args: Caps?, bytes: ByteArray?) {
            // Update UI from args
        }
    }

    init {
        cxrBridge.setStatusListener(/* StatusListener impl */)
        cxrBridge.subscribe(clientKey, msgCallback)
    }

    fun sendMessage(text: String) {
        cxrBridge.sendMessage(cmdKey, Caps().apply {
            write(“message”)
            write(text)
        })
    }
}

Constraints

• Channel keys, field order, and types must match on both sides.
• Register subscribe before relying on phone traffic; release on destroy per SDK guidance.
• Glasses do not call connect separately.

Key reporting uses the same sendMessage(“rk_custom_key”, …) channel — see Keys and System Broadcasts chapter.

Appendix: reference sample