Gradle代码输出不同名称的apk

在项目的model的Gradle下：

android {
defaultConfig {
        applicationId "XXX.XXX"
        minSdkVersion rootProject.ext.min_sdk_version
        targetSdkVersion rootProject.ext.target_sdk_version
        versionCode 12
        versionName "1.0.7"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
....
    applicationVariants.all { variant ->
        variant.outputs.all {
            // Rename APK
            def versionName = defaultConfig.versionName
            def date = new java.text.SimpleDateFormat("yyyyMMdd_HHmm").format(new Date())
            outputFileName = "app_${variant.buildType.name}_${versionName}_${date}.apk"
        }
    }
....
}

这样的话，生成的apk就不会覆盖原来的apk