All flavors must now belong to a named flavor dimension.

原因android studio 3.0新特性

解决办法

https://developer.android.com/studio/build/build-variants?utm_source=android-studio#flavor-dimensions

看不懂没关系
小白教程:

flavorDimensions "android" //productFlavors上面新添加一行
productFlavors {
        google {
            dimension "android"  //新添加一行
            manifestPlaceholders = [UMENG_CHANNEL_VALUE: "谷歌市场"]
        }
        baidu {
            dimension "android"//新添加一行
            manifestPlaceholders = [UMENG_CHANNEL_VALUE: "百度手机助手"]
        }
}

官方教程:

  // Specifies the flavor dimensions you want to use. The order in which you
  // list each dimension determines its priority, from highest to lowest,
  // when Gradle merges variant sources and configurations. You must assign
  // each product flavor you configure to one of the flavor dimensions.
  flavorDimensions "api", "mode"

  productFlavors {
    demo {
      // Assigns this product flavor to the "mode" flavor dimension.
      dimension "mode"
      ...
    }

    full {
      dimension "mode"
      ...
    }