BoxInsetLayout 由于没有窗口焦点而发生丢弃事件

Question

按照指南https://developer.android.com/training/wearables/apps/creating并用按钮 + 单击侦听器替换文本，Wear Emulator 中不会收到事件。

我在 Ubuntu 上使用 Android Studio 3.4.2

活动主文件

<?xml version="1.0" encoding="utf-8"?>
<androidx.wear.widget.BoxInsetLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/dark_grey"
    android:padding="@dimen/box_inset_layout_padding"
    tools:context=".MainActivity"
    tools:deviceIds="wear">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="@dimen/inner_frame_layout_padding"
        app:boxedEdges="all">

        <Button
            android:id="@+id/btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="btnClicker"
            android:text="Button" />

    </FrameLayout>
</androidx.wear.widget.BoxInsetLayout>

MainActivity.java

package com.example.watchtest;

import android.os.Bundle;
import android.support.wearable.activity.WearableActivity;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends WearableActivity {

    private TextView mTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Enables Always-on
        setAmbientEnabled();
    }

    public void btnClicker(View v) {
        Log.e("WATCH_TEST", "btnClicker");
    }
}

等级选项：

android {
    compileSdkVersion 28
    buildToolsVersion "29.0.1"
    defaultConfig {
        applicationId "com.example.watchtest"
        minSdkVersion 26
        targetSdkVersion 28

日志：

2019-07-21 10:30:00.464 8038-8038/? W/ViewRootImpl[MainActivity]: Dropping event due to no window focus: MotionEvent { action=ACTION_DOWN, actionButton=0, id[0]=0, x[0]=82.996826, y[0]=47.996826, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=5303462, downTime=5303462, deviceId=0, source=0x1002 }