BuildConfig 未正确创建（Gradle Android）

我正在尝试将我们的 Android 应用程序转换为 gradle 构建。我有这个项目，它的图书馆建设成功。我现在正在尝试为我们的各种环境创建单独的 apk（dev/test/prod 对它们使用的 restful 服务有不同的 url）。

在四处搜索时，我觉得最好的方法是为每个环境制作不同的 BuildConfig。这是我尝试过的：

import java.util.regex.Pattern

buildscript {
    repositories {
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:+'
    }
}

apply plugin: 'android'

task('increaseVersionCode') << {
    def manifestFile = file("AndroidManifest.xml")
    def pattern = Pattern.compile("versionCode=\"(\\d+)\"")
    def manifestText = manifestFile.getText()
    def matcher = pattern.matcher(manifestText)
    matcher.find()
    def versionCode = Integer.parseInt(matcher.group(1))
    def manifestContent = matcher.replaceAll("versionCode=\"" + ++versionCode + "\"")
    manifestFile.write(manifestContent)
}

tasks.whenTaskAdded { task ->
    if (task.name == 'generateReleaseBuildConfig') {
        task.dependsOn 'increaseVersionCode'
    }
}

dependencies {
    compile 'com.android.support:support-v4:19.0.0' 
    compile files('libs/commons-io-2.4.jar',
                  'libs/google-play-services.jar',
                  'libs/gson-2.2.4.jar',
                  'libs/universal-image-loader-1.8.6.jar',
                  'libs/wakeful-1.0.1.jar')
    compile project(':pulltorefresh_lib')
    compile project(':edgeeffect_lib')
    compile project(':viewpagerindicator_lib')        
}

android {
    buildToolsVersion "18.1.1"
    compileSdkVersion "Google Inc.:Google APIs:18"

    defaultConfig { 
       minSdkVersion 14
       targetSdkVersion 18
    }

    buildTypes {
        debug {
            packageNameSuffix ".debug"
        }
        dev.initWith(buildTypes.debug)
        dev {
            buildConfigField "String", "URL_SEARCH", "\"https://dev-search.example.com\";"
            buildConfigField "String", "URL_CONNECT", "\"https://dev-connect.example.com\";"
            buildConfigField "String", "URL_SVC_NEWSLIST", "\"https://dev-mobilenews.example.com/newslist\";"
            buildConfigField "String", "URL_SVC_NEWSDETAIL", "\"https://dev-mobilenews.example.com/newsdetail\";"
            buildConfigField "String", "URL_SVC_REGISTERENDPOINTS", "\"https://dev-mobilenews.example.com/registerendpoints\";"
        }
        prod.initWith(buildTypes.release)
        prod {
            buildConfigField "String", "URL_SEARCH", "\"https://search.example.com\";"
            buildConfigField "String", "URL_CONNECT", "\"https://connect.example.com\";"
            buildConfigField "String", "URL_SVC_NEWSLIST", "\"https://mobilenews.example.com/newslist\";"
            buildConfigField "String", "URL_SVC_NEWSDETAIL", "\"https://mobilenews.example.com/newsdetail\";"
            buildConfigField "String", "URL_SVC_REGISTERENDPOINTS", "\"https://mobilenews.pdc-np-cf.lmig.com/registerendpoints\";"          
        }
    }

    sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src']
            resources.srcDirs = ['src']
            res.srcDirs = ['res']
            assets.srcDirs = ['assets']
        }
    }
}

问题是我的 BuildConfig.java 似乎没有注入静态变量，因此我收到类似于以下内容的错误：

/Users/path/to/project/MainActivity.java:348: error: cannot find symbol
            startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(BuildConfig.URL_SEARCH)));
                                                                              ^
  symbol:   variable URL_SEARCH
  location: class BuildConfig
/Users/path/to/project/MainActivity.java:359: error: cannot find symbol
            startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(BuildConfig.URL_CONNECT)));
                                                                              ^
  symbol:   variable URL_CONNECT
  location: class BuildConfig
/Users/path/to/project/MainActivity.java:600: error: cannot find symbol
            HttpPost httpPost = new HttpPost(BuildConfig.URL_SVC_REGISTERENDPOINTS);
                                                        ^
  symbol:   variable URL_SVC_REGISTERENDPOINTS
  location: class BuildConfig
/Users/path/to/project/service/AlarmNotificationService.java:145: error: cannot find symbol
        String requestUrl = BuildConfig.URL_SVC_NEWSLIST + "?"
                                       ^
  symbol:   variable URL_SVC_NEWSLIST
  location: class BuildConfig
/Users/path/to/project/service/NewsService.java:240: error: cannot find symbol
        String requestUrl = BuildConfig.URL_SVC_NEWSLIST + "?"
                                       ^
  symbol:   variable URL_SVC_NEWSLIST
  location: class BuildConfig
/Users/path/to/project/service/NewsService.java:530: error: cannot find symbol
            HttpPost httpPost = new HttpPost(BuildConfig.URL_SVC_NEWSDETAIL);
                                                        ^
  symbol:   variable URL_SVC_NEWSDETAIL
  location: class BuildConfig
6 errors

我的 build/source/buildConfig/debug/com/.../BuildConfig.java 文件包含：

/**
 * Automatically generated file. DO NOT MODIFY
 */
package com....;

public final class BuildConfig {
  public static final boolean DEBUG = Boolean.parseBoolean("true");
  public static final String PACKAGE_NAME = "com.....debug";
  public static final String BUILD_TYPE = "debug";
  public static final String FLAVOR = "";
  public static final int VERSION_CODE = 5;
}

我究竟做错了什么？