Base64 not found - Android API level 26

[mingzhixian]

error：
java.lang.NoClassDefFoundError: Failed resolution of: Ljava/util/Base64;

Looks like java.util.Base64 is only available on Android starting with API level 26. On older Android versions we'd need to use android.util.Base64

[bartekpacia]

We could also use base64 from Kotlin's stdlib.