为什么我的vaadin按钮无法正确显示？

Question

几乎是标题，我到处都在寻找答案，但是我要么错过了一些设置，春天就错过了，摇摇欲坠，要么我看不懂。

我认为我的页面应该是一个漂亮的蓝色按钮或某种东西（我知道我删除了网格），我遵循了https://www.baeldung.com/spring-boot-vaadin，但我却得到了this，这是我的build.gradle和相关代码：

build.gradle：

plugins {
    id 'org.jetbrains.kotlin.plugin.jpa' version '1.3.21'
    id 'org.springframework.boot' version '2.1.3.RELEASE'
    id 'org.jetbrains.kotlin.jvm' version '1.3.21'
    id 'org.jetbrains.kotlin.plugin.spring' version '1.3.21'
    id 'com.devsoap.vaadin-flow' version '1.0'
    //id 'org.gretty' version '2.3.1'
    id 'java'
    // solves the problem with long classpath using JAR instead of classpath on command line
    id "ua.eshepelyuk.ManifestClasspath" version "1.0.0"
}

vaadin {
    version '12.0.0'
}

apply plugin: 'io.spring.dependency-management'

version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

springBoot {
    mainClassName = "com.cpsc471.TheatreManagmentApplicationKt"
}

repositories {
    mavenCentral()
    maven { url "https://maven.vaadin.com/vaadin-addons" }
    vaadin.repositories()
    // Add the pre-release repository
    vaadin.prereleases()
    // Add the snapshot repository
    vaadin.snapshots()
    // Add the addons repository
    vaadin.addons()
}

ext {
    set('vaadinVersion', '13.0.1')
}

noArg{
    annotation("MappedSuperclass")
}

dependencies { 
    implementation 'org.springframework.boot:spring-boot-starter-cache'
    implementation 'org.springframework.boot:spring-boot-starter-data-rest'
    implementation 'org.springframework.boot:spring-boot-starter-jdbc'
    implementation 'org.springframework.boot:spring-boot-starter-mail'
    implementation 'org.springframework.boot:spring-boot-starter-security'
    implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
    implementation 'org.springframework.boot:spring-boot-starter-validation'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-tomcat'
    implementation "org.springframework.boot:spring-boot-starter-data-jpa"
    implementation 'com.fasterxml.jackson.module:jackson-module-kotlin'
    implementation 'com.vaadin:vaadin-spring-boot-starter:13.0.2'
    implementation 'org.jetbrains.kotlin:kotlin-reflect'
    implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
    implementation 'org.springframework.retry:spring-retry' 

    implementation 'com.h2database:h2'

    implementation vaadin.bom()
    implementation vaadin.platform()
    implementation vaadin.lumoTheme()
    compile vaadin.springBoot()

    compileOnly 'org.projectlombok:lombok'

    runtimeOnly 'org.springframework.boot:spring-boot-devtools'
    runtimeOnly 'org.postgresql:postgresql'

    annotationProcessor 'org.projectlombok:lombok'

    testImplementation 'org.springframework.boot:spring-boot-starter-test'
    testImplementation 'org.springframework.security:spring-security-test'
}

dependencyManagement {
    imports {
        mavenBom "com.vaadin:vaadin-bom:${vaadinVersion}"
    }
}

compileKotlin {
    kotlinOptions {
        freeCompilerArgs = ['-Xjsr305=strict']
        jvmTarget = '1.8'
    }
}

compileTestKotlin {
    kotlinOptions {
        freeCompilerArgs = ['-Xjsr305=strict']
        jvmTarget = '1.8'
    }
}

MainView：

import com.cpsc471.model.types.User;
import com.vaadin.flow.component.button.Button;
import com.vaadin.flow.component.grid.Grid;
import com.vaadin.flow.component.icon.VaadinIcon;
import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.component.textfield.TextField;
import com.vaadin.flow.data.value.ValueChangeMode;
import com.vaadin.flow.router.Route;

@Route(value = "test")
public class MainView extends VerticalLayout {

    private EmployeeEditor editor;
    private TextField filter;
    private Button addNewBtn;

    public MainView (EmployeeEditor editor) {
        setSizeFull();
        this.editor = editor;
        this.filter = new TextField();
        this.addNewBtn = new Button("New employee", VaadinIcon.PLUS.create());

        HorizontalLayout actions = new HorizontalLayout(filter, addNewBtn);
        add(actions, editor);

        filter.setPlaceholder("Filter by last name");
        filter.setValueChangeMode(ValueChangeMode.EAGER);
    }
}

自定义组件：

package com.cpsc471.model;

import com.cpsc471.model.types.User;
import com.vaadin.flow.component.KeyNotifier;
import com.vaadin.flow.component.button.Button;
import com.vaadin.flow.component.icon.VaadinIcon;
import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.component.textfield.TextField;
import com.vaadin.flow.data.binder.Binder;
import com.vaadin.flow.spring.annotation.SpringComponent;
import com.vaadin.flow.spring.annotation.UIScope;

import javax.swing.plaf.basic.BasicMenuUI;

@SpringComponent
@UIScope
public class EmployeeEditor extends VerticalLayout implements KeyNotifier {
    private User employee;

    private TextField firstName = new TextField("First name");
    private TextField lastName = new TextField("Last name");

    private Button save = new Button("Save", VaadinIcon.CHECK.create());
    private Button cancel = new Button("Cancel");
    private Button delete = new Button("Delete", VaadinIcon.TRASH.create());

    private HorizontalLayout actions = new HorizontalLayout(save, cancel, delete);
    private Binder<User> binder = new Binder<>(User.class);
    private BasicMenuUI.ChangeHandler changeHandler;
}

spring boot应用程序（kotlin）：

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.context.annotation .Bean
import org.springframework.context.annotation .Configuration
import org.springframework.security.config.annotation .web.builders.HttpSecurity
import org.springframework.security.config.annotation .web.configuration.EnableWebSecurity
import org.springframework.security.config.annotation .web.configuration.WebSecurityConfigurerAdapter
import org.springframework.security.core.userdetails.User
import org.springframework.security.core.userdetails.UserDetailsService
import org.springframework.security.provisioning.InMemoryUserDetailsManager
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer

import org.springframework.boot.SpringApplication
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer

@SpringBootApplication
class TheatreManagmentApplication : SpringBootServletInitializer()

fun main(args: Array<String>) {
    SpringApplication.run(TheatreManagmentApplication::class.java, *args)
}

@Configuration
@EnableWebSecurity
class WebSecurityConfig : WebSecurityConfigurerAdapter() {
    @Throws(Exception::class)
    protected override fun configure(http: HttpSecurity) {
        http
                .authorizeRequests()
                .antMatchers("/", "/home","/h2/**").permitAll()
                .anyRequest().authenticated()
                .and()
                .formLogin()
                .loginPage("/login")
                .permitAll()
                .and()
                .logout()
                .permitAll()

        http.csrf().disable()
        http.headers().frameOptions().disable()
    }

    @Bean
    override fun userDetailsService(): UserDetailsService {
        val user = User.withDefaultPasswordEncoder()
                .username("user")
                .password("password")
                .roles("USER")
                .build()

        return InMemoryUserDetailsManager(user)
    }
}

@Configuration
class MvcConfig : WebMvcConfigurer {
    override fun addViewControllers(registry: ViewControllerRegistry) {
        registry.addViewController("/home").setViewName("home")
        registry.addViewController("/").setViewName("home")
        registry.addViewController("/hello").setViewName("hello")
        registry.addViewController("/login").setViewName("login")
    }
}