How to fix appcompat error in android studio

Question

I want to work with firebase real time database and when I implement firebase core and firebase database library appcompat get error. My app module code is below?

 android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.example.mahdi.smsreviver"
        minSdkVersion 15
        targetSdkVersion 27
        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 'com.android.support:appcompat-v7:27.1.1'
        implementation 'com.android.support.constraint:constraint-layout:1.1.3'
        implementation 'com.google.firebase:firebase-database: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.google.firebase:firebase-core:16.0.7'
    }

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

Answer 1

Don't use appcompat, Use AndroidX the new support version library from Google. It has better compatibility features and other noticeable features. Besides Appcompat is so Old.

Answer 2

from firebase release note you are using the latest version(firebase-core 16.0.7) which conflicts with appcompat version(27.1.1)

so please update gradle

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.mahdi.smsreviver"
        minSdkVersion 15
        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 'com.android.support:appcompat-v7.28.0.0'
    implementation 'com.google.firebase:firebase-database:16.0.6'

    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-core:16.0.7'
}

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