IONIC-Dex：将字节码转换为dex时出错：-targetCompatibility ='1.7'sourceCompatibility ='1.7'

Question

targetCompatibility ='1.7' sourceCompatibility ='1.7'

   Dex: Error converting bytecode to dex:
Cause: Dex cannot parse version 52 byte code.
This is caused by library dependencies that have been compiled using Java 8 or above.
If you are using the 'java' gradle plugin in a library submodule add
targetCompatibility = '1.7'
sourceCompatibility = '1.7'
to that submodule's build.gradle file.
    UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.RuntimeException: Exception parsing classes

请帮助，面对Ionic 3的问题