Cannot fit requested classes in a single dex file (# methods: 84272 > 65536) code example

Example 1: cannot fit requested classes in a single dex file

//Add the library in app gradle
implementation 'com.android.support:multidex:1.0.3'

//Add this to the default config in the app gradle
multiDexEnabled true
  
//If this still doesn't work, consider adding this name into the android manifesto
android:name=".MyApplication"

Example 2: Cannot fit requested classes in a single dex file (# methods: 65710 > 65536)

android {
    defaultConfig {
        ...
        minSdkVersion 21 <----- *here
        targetSdkVersion 26
        multiDexEnabled true <------ *here
    }
    ...
}