未解析的引用。由于接收器类型不匹配,以下任何候选项都不适用

我在用 androidx navigation architecture 随着 Kotlin 1.2.71 在Android Studio 3.2.1中。我的片段代码是:

package com.dell.andnav.fragments

import android.os.Bundle
import android.support.v4.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import androidx.navigation.fragment.findNavController
import com.dell.andnav.R
import kotlinx.android.synthetic.main.fragment_welcome.*


/**
 * A simple [Fragment] subclass.
 * Use the [WelcomeFragment.newInstance] factory method to
 * create an instance of this fragment.
 *
 */
class WelcomeFragment : Fragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_welcome, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        detailButton.setOnClickListener {
            findNavController().navigate(R.id.action_welcomeFragment_to_detailsFragment)
        }
    }

    companion object {
        @JvmStatic
        fun newInstance() = WelcomeFragment()
    }
}  

布局代码为:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:id="@+id/frameLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".fragments.WelcomeFragment">


    <Button
        android:id="@+id/detailButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/to_detail_fragment"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>  

我的build.gradle是:

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'androidx.navigation.safeargs'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.dell.andnav"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        androidExtensions {
            experimental = true
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    def nav_version = "1.0.0-alpha07"
    implementation fileTree(dir: 'libs', include: ['*.jar'])
//    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
//    implementation 'com.android.support:support-v4:28.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

    implementation 'androidx.lifecycle:lifecycle-extensions:2.0.0'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'androidx.multidex:multidex:2.0.0'
    implementation 'androidx.appcompat:appcompat:1.0.2'

    implementation "android.arch.navigation:navigation-fragment-ktx:$nav_version"
    implementation "android.arch.navigation:navigation-ui-ktx:$nav_version"

    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}
repositories {
    mavenCentral()
}

当我试图运行我的代码时,我得到以下错误:

未解析的引用。由于接收器类型不匹配,以下任何候选项都不适用: public val activity.detailbutton:按钮!在kotlinx.android.synthetic.main.fragment中定义欢迎 public val dialog.detailbutton:按钮!在kotlinx.android.synthetic.main.fragment中定义欢迎 public val android.app.fragment.detailbutton:按钮!在kotlinx.android.synthetic.main.fragment中定义欢迎 public val androidx.fragment.app.fragment.detailButton:按钮!在kotlinx.android.synthetic.main.fragment中定义欢迎 public val layoutContainer.detailButton:按钮!在kotlinx.android.synthetic.main.fragment中定义欢迎

如何解决该错误?