Não consigo importar LocationCallback / FusedLocationProviderClient

import android.annotation.SuppressLint;
import android.content.Context;

public class GPS extends LocationCallback {

    private FusedLocationProviderClient client;


    public GPS(Context context) {
        this.client = LocationServices.getFusedLocationProviderClient(context);
    }

    public void fazBusca() {
        LocationRequest req = new LocationRequest();

        req.setInterval(1000);
        req.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
        req.setSmallestDisplacement(10);

        client.requestLocationUpdates(req, this, null);
    }


    @Override
    public void onLocationResult(LocationResult locationResult) {
        super.onLocationResult(locationResult);

        // trabalha com o resultado
    }


    public void cancelaBusca() {
        client.removeLocationUpdates(this);
    }
}

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.agenda"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    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.google.android.gms:play-services-maps:16.1.0'
    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.android.support:cardview-v7:28.0.0'
    implementation 'com.google.gms:google-services:3.1.1'
}