Android design support library for API 28 (P) not working

Solution 1:

You can either use the previous API packages version of artifacts or the new Androidx, never both.

If you wanna use the previous version, replace your dependencies with

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:28.0.0-alpha3'
    implementation 'com.android.support.constraint:constraint-layout:1.1.1'

    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:design:28.0.0-alpha3'
    implementation 'com.android.support:cardview-v7:28.0.0-alpha3'
}

if you want to use Androidx:

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'androidx.appcompat:appcompat:1.0.0-alpha3'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.1'

    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.1.0-alpha3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0-alpha3'

    implementation 'com.google.android.material:material:1.0.0-alpha3'
    implementation 'androidx.cardview:cardview:1.0.0-alpha3'
}

Solution 2:

Important Update

Android will not update support libraries after 28.0.0.

This will be the last feature release under the android.support packaging, and developers are encouraged to migrate to AndroidX 1.0.0.

So use library AndroidX.

• Don't use both Support and AndroidX in project.
• Your library module or dependencies can still have support libraries. Androidx Jetifier will handle it.
• Use stable version of androidx or any library, because alpha, beta, rc can have bugs which you dont want to ship with your app.

In your case

dependencies {
    implementation 'androidx.appcompat:appcompat:1.0.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.1'

    implementation 'com.google.android.material:material:1.0.0'
    implementation 'androidx.cardview:cardview:1.0.0'
}

Solution 3:

Add this:

tools:replace="android:appComponentFactory"
android:appComponentFactory="whateverString"

to your manifest application

<application
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    tools:replace="android:appComponentFactory"
    android:appComponentFactory="whateverString">

hope it helps