How to send String via DataItem

I can't connect my watchface with a handheld app. I want to send a simple text (on click button in the handheld) for understanding how it works. Unfortunately, I'm missing something because I have not any message in the watchface.

My onClickListener in the handheld MainActivity

sendDataItem.setOnClickListener {
            val putDataReq: PutDataRequest = PutDataMapRequest.create("/test").run {
                dataMap.putString("key", "TEST TEXT")
                asPutDataRequest()
            }
            val putDataTask: Task<DataItem> = dataClient.putDataItem(putDataReq)
        }

My override OnDataChanged method that (what I at least want to do) send data to my watchface

override fun onDataChanged(dataEvents: DataEventBuffer) {
            dataEvents.forEach { event ->
                // DataItem changed
                if (event.type == DataEvent.TYPE_CHANGED) {
                    event.dataItem.also { item ->
                        if (item.uri.path.compareTo("/test") == 0) {
                            DataMapItem.fromDataItem(item).dataMap.apply {
                                weatherTemp = getString("key")
                            }
                        }
                    }
                } else if (event.type == DataEvent.TYPE_DELETED) {
                    // DataItem deleted
                }
            }
        }

I want a simple result. As soon I receive data I want to save it to weatherTemp var.

I spend some time on this but finally, I get this working. In my watch face class I have onDataChange method that is receiving data item:

override fun onDataChanged(dataEvents: DataEventBuffer) {
            dataEvents.forEach { event ->
                if (event.type == DataEvent.TYPE_CHANGED) {
                    val path = event.dataItem.uri.path
                    event.dataItem.also { item ->
                        if (path.compareTo("/testPath") == 0) {
                            DataMapItem.fromDataItem(item).dataMap.apply {
                               //I'm changing var that is printed on the watchface screen
                                testVar = getInt("key").toString()
                            }
                        }
                    }
                } else if (event.type == DataEvent.TYPE_DELETED) {
                    //DataItem deleted
                } else {
                    //Unknown data type event
                }
            }
        }

You cannot forget about:

 Wearable.getDataClient(applicationContext).addListener(this)

in your onCreate method. I'm sending data item from my handheld activity on button press.

sendDataItem.setOnClickListener {
            putDataMapReq = PutDataMapRequest.create("/testPath")
            putDataMapReq.dataMap.putInt("key", testVar++)
            putDataReq = putDataMapReq.asPutDataRequest()
            putDataReq.setUrgent()
            putDataTask = Wearable.getDataClient(applicationContext).putDataItem(putDataReq)
        }

It's not perfect but at least it's working and I'm able to go ahead. If anything is unclear feel free to write the comment.