title: Could not resolve com.android.support:support-annotations:25.4.0
body: <p>I use flutter to make an app. while I excute <code>flutte run</code> in console (I use Tor as http and https proxy in console cause google restrictions and USA sanctions for some countries), I get an error like this:</p>
  
  <pre><code>[iraj@iraj-pc app]$ flutter run
  
  Launching lib/main.dart on LG K520 in debug mode...
  Initializing gradle...                                0.5s
  Resolving dependencies...                                 
  Error running gradle: Exit code 1 from: /home/iraj/Public/dart/exercise_flutter/app/android/gradlew app:properties:
  NDK is missing a "platforms" directory.
  If you are using NDK, verify the ndk.dir is set to a valid NDK directory.  It is currently set to /home/iraj/Public/bin/android-sdk-linux/ndk-bundle.
  If you are not using NDK, unset the NDK variable from ANDROID_NDK_HOME or local.properties to remove this warning.
  
  Incremental java compilation is an incubating feature.
  Failed to validate the XML for the repository at URL 'https://dl.google.com/android/repository/repository2-1.xml/repository-12.xml'
  Errors during XML parse:
  White spaces are required between publicId and systemId.
  org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 62; White spaces are required between publicId and systemId.
  javax.xml.bind.UnmarshalException
   - with linked exception:
  [org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 62; White spaces are required between publicId and systemId.]
  Additionally, the fallback loader failed to parse the XML.
  Failed to validate the XML for the repository at URL 'https://dl.google.com/android/repository/repository2-1.xml/repository-12.xml/sys-img.xml'
  Failed to validate the XML for the repository at URL 'https://dl.google.com/android/repository/repository2-1.xml/repository-12.xml/addon.xml'
  Errors during XML parse:
  White spaces are required between publicId and systemId.
  org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 62; White spaces are required between publicId and systemId.
  javax.xml.bind.UnmarshalException
   - with linked exception:
  [org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 62; White spaces are required between publicId and systemId.]
  Additionally, the fallback loader failed to parse the XML.
  
  BUILD FAILED
  
  Total time: 2 mins 24.903 secs
  
  [Fatal Error] support-annotations-25.4.0.pom:2:10: Already seen doctype.
  [Fatal Error] support-annotations-25.4.0.pom:2:10: Already seen doctype.
  
  FAILURE: Build failed with an exception.
  
  * Where:
  Build file '/home/iraj/Public/dart/exercise_flutter/app/android/build.gradle' line: 26
  
  * What went wrong:
  A problem occurred evaluating root project 'android'.
  &gt; A problem occurred configuring project ':app'.
     &gt; Could not resolve all dependencies for configuration ':app:_debugAndroidTestApkCopy'.
        &gt; Could not resolve com.android.support:support-annotations:25.4.0.
          Required by:
              project :app
           &gt; Could not resolve com.android.support:support-annotations:25.4.0.
              &gt; Could not parse POM https://maven.google.com/com/android/support/support-annotations/25.4.0/support-annotations-25.4.0.pom
                 &gt; Already seen doctype.
        &gt; Could not resolve com.android.support:support-annotations:25.4.0.
          Required by:
              project :app &gt; com.android.support.test:runner:0.5
           &gt; Could not resolve com.android.support:support-annotations:25.4.0.
              &gt; Could not parse POM https://maven.google.com/com/android/support/support-annotations/25.4.0/support-annotations-25.4.0.pom
                 &gt; Already seen doctype.
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
  Running 'gradlew assembleDebug'...                        
  [Fatal Error] support-annotations-25.4.0.pom:2:10: Already seen doctype.
  [Fatal Error] support-annotations-25.4.0.pom:2:10: Already seen doctype.
  
  FAILURE: Build failed with an exception.
  
  * Where:
  Build file '/home/iraj/Public/dart/exercise_flutter/app/android/build.gradle' line: 26
  
  * What went wrong:
  A problem occurred evaluating root project 'android'.
  &gt; A problem occurred configuring project ':app'.
     &gt; Could not resolve all dependencies for configuration ':app:_debugAndroidTestApkCopy'.
        &gt; Could not resolve com.android.support:support-annotations:25.4.0.
          Required by:
              project :app
           &gt; Could not resolve com.android.support:support-annotations:25.4.0.
              &gt; Could not parse POM https://maven.google.com/com/android/support/support-annotations/25.4.0/support-annotations-25.4.0.pom
                 &gt; Already seen doctype.
        &gt; Could not resolve com.android.support:support-annotations:25.4.0.
          Required by:
              project :app &gt; com.android.support.test:runner:0.5
           &gt; Could not resolve com.android.support:support-annotations:25.4.0.
              &gt; Could not parse POM https://maven.google.com/com/android/support/support-annotations/25.4.0/support-annotations-25.4.0.pom
                 &gt; Already seen doctype.
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
  Gradle build failed: 1
  </code></pre>
  
  <p>flutter version:</p>
  
  <pre><code>flutter --version  
  Flutter • channel alpha • https://github.com/flutter/flutter.git
  Framework • revision b156a0f054 (2 weeks ago) • 2017-08-11 22:01:40 -0700
  Engine • revision fef7d827d6
  Tools • Dart 1.25.0-dev.9.0
  </code></pre>
  
  <p>dart version:</p>
  
  <pre><code>[iraj@iraj-pc app]$ dart --version
  Dart VM version: 1.24.2 (Thu Jun 22 08:43:26 2017) on "linux_x64"
  </code></pre>
  
  <p>android targets:</p>
  
  <pre><code>[iraj@iraj-pc app]$ android list target
  Available Android targets:
  ----------
  id: 1 or "android-23"
       Name: Android 6.0
       Type: Platform
       API level: 23
       Revision: 3
       Skins: HVGA, QVGA, WQVGA400, WQVGA432, WSVGA, WVGA800 (default), WVGA854, WXGA720, WXGA800, WXGA800-7in
   Tag/ABIs : no ABIs.
  ----------
  id: 2 or "android-24"
       Name: Android 7.0
       Type: Platform
       API level: 24
       Revision: 2
       Skins: HVGA, QVGA, WQVGA400, WQVGA432, WSVGA, WVGA800 (default), WVGA854, WXGA720, WXGA800, WXGA800-7in
   Tag/ABIs : default/armeabi-v7a
  ----------
  id: 3 or "android-25"
       Name: Android 7.1.1
       Type: Platform
       API level: 25
       Revision: 3
       Skins: HVGA, QVGA, WQVGA400, WQVGA432, WSVGA, WVGA800 (default), WVGA854, WXGA720, WXGA800, WXGA800-7in
   Tag/ABIs : google_apis/armeabi-v7a
  ----------
  id: 4 or "Google Inc.:Google APIs:23"
       Name: Google APIs
       Type: Add-On
       Vendor: Google Inc.
       Revision: 1
       Description: Android + Google APIs
       Based on Android 6.0 (API level 23)
       Libraries:
        * com.android.future.usb.accessory (usb.jar)
            API for USB Accessories
        * com.google.android.media.effects (effects.jar)
            Collection of video effects
        * com.google.android.maps (maps.jar)
            API for Google Maps
       Skins: HVGA, QVGA, WQVGA400, WQVGA432, WSVGA, WVGA800 (default), WVGA854, WXGA720, WXGA800, WXGA800-7in
   Tag/ABIs : no ABIs.
  </code></pre>
  
  <p>could not even find <code>support-annotations-25.4.0</code> in maven and jcenter repositories. 
  what is the problem?</p>