android studio 不支持 java 8?

本机环境为装且仅装jdk 1.8.0_45，配置无误，安卓项目编译运行正常，但是我需要用几个java8的新特性却出现问题：

用lambda 语法和method reference语法在android studio 里都没有报错，但是一编译就会出现

error: lambda expression are not support in -source 1.7
(use -source 8 to enable)

我在gradle里加上java版本

compileOptions{
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}

就会报错：

Error:Execution failed for task ':app:dexDebug'.
> com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1


附上整个环境：

apply plugin: 'com.android.application'

android {
compileSdkVersion 22
buildToolsVersion '22.0.1'

defaultConfig {
applicationId "com.example.zj299.activityswitcher"
minSdkVersion 22
targetSdkVersion 22
versionCode 1
versionName "1.0"
}
compileOptions{
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
compileOptions {
}
}

dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
compile 'com.android.support:appcompat-v7:22.2.0'
compile 'com.google.android.gms:play-services:7.5.0'
}