I am getting this error.

I also added

ext {
minSdkVersion = 19
compileSdkVersion = 29
targetSdkVersion = 29
buildToolsVersion = "29.0.2"
}

in the top-level gradle fle.

and in the module leve

compileSdkVersion rootProject.ext.compileSdkVersion
buildToolsVersion rootProject.ext.buildToolsVersion

defaultConfig {
    minSdkVersion rootProject.ext.minSdkVersion
    targetSdkVersion rootProject.ext.targetSdkVersion
    versionCode 1
    versionName "1.0"
}