Can't Build Project After Adding Firebase Dependency

I am trying to test out FCM but after adding the firebase-messaging dependency the app can't build. I'm getting some warning along the lines of "WARNING: API 'variant.getMergeResources()' is obsolete and has been replaced with 'variant.getMergeResourcesProvider()'. It will be removed at the end of 2019."

The error I'm getting is:

"Dependencies using groupId com.android.support and androidx.* can not be combined but found IdeMavenCoordinates{myGroupId='com.android.support', myArtifactId='appcompat-v7', myVersion='28.0.0', myPacking='aar', myClassifier='null'} and IdeMavenCoordinates{myGroupId='androidx.slidingpanelayout', myArtifactId='slidingpanelayout', myVersion='1.0.0', myPacking='aar', myClassifier='null'}...

on the line:

implementation 'com.android.support:appcompat-v7:28.0.0'

I've tried a solution that involves adding some "configurations.all" option to the gradle file but that didn't work. I've tried changing the version of firebase to an earlier one and that doesn't work either.

This is my build that module level build.gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.hfad.fcm"
        minSdkVersion 19
        targetSdkVersion 28
        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(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    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-messaging:19.0.1'
}

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

The error says you cannot combine appcompat and androidx libraries, So move your dependencies to androidx , You should use androidx libraries:

implementation 'androidx.appcompat:appcompat:1.0.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

Here you can see my own dependencies for firebase messaging:

implementation 'androidx.appcompat:appcompat:1.0.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'com.google.firebase:firebase-core:16.0.1'
implementation 'com.google.firebase:firebase-messaging:17.3.4'

find versions from here https://developer.android.com/jetpack/androidx/migrate