Android Studio JDK版本问题报错

Android Studio import包后就报错，是因为JDK版本问题

报错：

Error: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.

解决办法：

在project下的build.gradle改成这样：

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.1.0'
        apply plugin: 'java'
        sourceCompatibility = 1.7
        targetCompatibility = 1.7
    }
}

在app文件夹下的build.gradle改成这样：