Android Studio依赖项解析

Question

我下载了Android Studio 3.0并希望运行我的第一个应用程序（只使用工作室的默认代码并显示空白活动）。
但我不断收到以下错误。

第一条错误消息：

Unable to resolve dependency for ':app@debug/compileClasspath': Could not 
resolve com.android.support:appcompat-v7:26.1.0.
Could not resolve com.android.support:appcompat-v7:26.1.0.
   Required by:
     project :app
       >Could not resolve com.android.support:appcompat-v7:26.1.0.
         > Could not get resource 
     'https://dl.google.com/dl/android/maven2/com/android/support/appcompat-
          v7/26.1.0/appcompat-v7-26.1.0.pom'.
             > Could not GET 
     'https://dl.google.com/dl/android/maven2/com/android/support/appcompat-
     v7/26.1.0/appcompat-v7-26.1.0.pom'.
               > dl.google.com

第二条错误消息：

    Unable to resolve dependency for ':app@debugAndroidTest/compileClasspath': 
    Could not resolve com.android.support.test:runner:1.0.1.
    Could not resolve com.android.support.test:runner:1.0.1.
     Required by:
       project :app
          > Could not resolve com.android.support.test:runner:1.0.1.
             > Could not get resource 

      'https://dl.google.com/dl/android/maven2/com/android/support/test/runner/ 
       1.0.1/runner-1.0.1.pom'.
          > Could not GET 
        'https://dl.google.com/dl/android/maven2/com/android/support/test/runner 
         /1.0.1/runner-1.0.1.pom'.
                   > dl.google.com