导入com.google.android.gms.auth.api.auth的未解析引用

我正在学习如何开发一个带有谷歌登录选项的应用程序，我正在关注这一点。但是，我的活动不是注册导入com.google.android.gms.auth.api.auth，也不是在导入时用红色标记

auth

package nus.is3261.kotlinapp

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_google_signin.*
import com.google.android.gms.auth.api.Auth
import com.google.android.gms.common.api.GoogleApiClient
import com.google.firebase.auth.FirebaseAuth
import com.google.android.gms.auth.api.signin.GoogleSignInOptions
import com.google.android.gms.common.ConnectionResult
import com.google.firebase.auth.FirebaseUser
import android.content.Intent
import com.google.android.gms.auth.api.signin.GoogleSignInAccount
import com.google.firebase.auth.GoogleAuthProvider

class GoogleSigninActivity : AppCompatActivity(), View.OnClickListener, GoogleApiClient.OnConnectionFailedListener {

    private val TAG = "JSAGoogleSignIn"
    private val REQUEST_CODE_SIGN_IN = 1234
    private val WEB_CLIENT_ID = "xxxxxx.apps.googleusercontent.com"

    private var mAuth: FirebaseAuth? = null

    private var mGoogleApiClient: GoogleApiClient? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_google_signin)

        btn_sign_in.setOnClickListener(this)
        btn_sign_out.setOnClickListener(this)
        btn_disconnect.setOnClickListener(this)

        val gso = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(WEB_CLIENT_ID)
                .requestEmail()
                .build()

        mGoogleApiClient = GoogleApiClient.Builder(this)
                .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
                .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                .build()

        mAuth = FirebaseAuth.getInstance()
    }

    override fun onStart() {
        super.onStart()

        // Check if user is signed in (non-null) and update UI accordingly.
        val currentUser = mAuth!!.currentUser
        updateUI(currentUser)
    }

    override fun onClick(v: View?) {
        val i = v!!.id

        when (i) {
            R.id.btn_sign_in -> signIn()
            R.id.btn_sign_out -> signOut()
            R.id.btn_disconnect -> revokeAccess()
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent();
        if (requestCode == REQUEST_CODE_SIGN_IN) {
            val result = Auth.GoogleSignInApi.getSignInResultFromIntent(data)
            if (result.isSuccess) {
                // successful -> authenticate with Firebase
                val account = result.signInAccount
                firebaseAuthWithGoogle(account!!)
            } else {
                // failed -> update UI
                updateUI(null)
                Toast.makeText(applicationContext, "SignIn: failed!",
                        Toast.LENGTH_SHORT).show()
            }
        }
    }

    private fun firebaseAuthWithGoogle(acct: GoogleSignInAccount) {
        Log.e(TAG, "firebaseAuthWithGoogle():" + acct.id!!)

        val credential = GoogleAuthProvider.getCredential(acct.idToken, null)
        mAuth!!.signInWithCredential(credential)
                .addOnCompleteListener(this) { task ->
                    if (task.isSuccessful) {
                        // Sign in success
                        Log.e(TAG, "signInWithCredential: Success!")
                        val user = mAuth!!.currentUser
                        updateUI(user)
                    } else {
                        // Sign in fails
                        Log.w(TAG, "signInWithCredential: Failed!", task.exception)
                        Toast.makeText(applicationContext, "Authentication failed!",
                                Toast.LENGTH_SHORT).show()
                        updateUI(null)
                    }
                }
    }

    override fun onConnectionFailed(connectionResult: ConnectionResult) {
        Log.e(TAG, "onConnectionFailed():" + connectionResult);
        Toast.makeText(applicationContext, "Google Play Services error.", Toast.LENGTH_SHORT).show();
    }

    private fun signIn() {
        val intent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient)
        startActivityForResult(intent, REQUEST_CODE_SIGN_IN)
    }

    private fun signOut() {
        // sign out Firebase
        mAuth!!.signOut()

        // sign out Google
        Auth.GoogleSignInApi.signOut(mGoogleApiClient).setResultCallback { updateUI(null) }
    }

    private fun revokeAccess() {
        // sign out Firebase
        mAuth!!.signOut()

        // revoke access Google
        Auth.GoogleSignInApi.revokeAccess(mGoogleApiClient).setResultCallback { updateUI(null) }
    }

    private fun updateUI(user: FirebaseUser?) {
        if (user != null) {
            tvStatus.text = "Google User email: " + user.email!!
            tvDetail.text = "Firebase User ID: " + user.uid

            btn_sign_in.visibility = View.GONE
            layout_sign_out_and_disconnect.visibility = View.VISIBLE
        } else {
            tvStatus.text = "Signed Out"
            tvDetail.text = null

            btn_sign_in.visibility = View.VISIBLE
            layout_sign_out_and_disconnect.visibility = View.GONE
        }
    }
}

我觉得这是一个依赖性问题，但我不确定问题在哪里

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'
apply plugin: 'com.google.gms.google-services'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "nus.is3261.kotlinapp"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    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'
    implementation 'com.android.support:design: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 'com.google.firebase:firebase-auth:16.0.5'
    implementation 'com.google.firebase:firebase-core:16.0.4'

}

这是我的gradle档案

buildscript {
    ext.kotlin_version = '1.2.70'
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.1.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files

    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

---

在依赖项中添加：

implementation 'com.google.android.gms:play-services-auth:16.0.1'

然后在app/build.gradle文件的底部添加（firebase所需）：

---

天哪，谢谢！在添加了

实现之后

它起作用了，我已经在页面顶部设置了

apply plugin

，如果它位于页面底部，位置是否重要？是的，最好将它添加到页面底部，因为我已经看到了它不存在时的问题，也因为文档中提到了它。注意，无论何时使用任何库，都需要将其添加到Dependencies中，以便能够在代码中使用它。

apply plugin: 'com.google.gms.google-services'