未解决的参考。由于接收器类型不匹配，以下候选都不适用

Question

我在 Android studio 3.2.1 中使用androidx navigation architecturewith Kotlin 1.2.71。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()
    }
}  

布局代码是：

<?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()
}

当我尝试运行我的代码时，出现以下错误：

未解决的参考。由于接收器类型不匹配，以下候选者都不适用： public val Activity.detailButton: Button! 定义在 kotlinx.android.synthetic.main.fragment_welcome public val Dialog.detailButton: Button! 在 kotlinx.android.synthetic.main.fragment_welcome public val android.app.Fragment.detailButton 中定义：按钮！定义在 kotlinx.android.synthetic.main.fragment_welcome public val androidx.fragment.app.Fragment.detailButton: 按钮！定义在 kotlinx.android.synthetic.main.fragment_welcome public val LayoutContainer.detailButton: Button! 在 kotlinx.android.synthetic.main.fragment_welcome 中定义

我该如何解决该错误？

Answer 1

您正在访问的按钮位于您的片段内，但您正在直接访问它。您应该像我们使用 java 一样通过父视图访问它，rootview.findViewById()因此请使用

view.detailButton.setOnClickListener {
    findNavController().navigate(R.id.action_welcomeFragment_to_detailsFragment)
}