问题：

Error:Library projects cannot set applicationId. applicationId is set to ‘hailou.demosandapis’ in default config.

解决：

在build.gradle中，将applicationId注释掉。

    defaultConfig {
        /*applicationId "hailou.demosandapis"*/
        minSdkVersion 24
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }