title: Gradle error - Execution failed for task ':app:dexDebug'
body: <p>I am trying to add the MPAndroidChartLibrary to my Android Studio project, however when I try to run the app, it keeps failing with 1 error. I am not very good with gradle, so I don't really know whats going wrong.</p>
  
  <p>My gradle file is this:</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 21
      buildToolsVersion "21.0.2"
  
      defaultConfig {
          applicationId "com.bacon.corey.audiotimeshift"
          minSdkVersion 16
          targetSdkVersion 21
          versionCode 1
          versionName "1.0"
      }
      buildTypes {
          release {
              runProguard false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  repositories {
      flatDir {
          dirs 'libs'
      }
  }
  
  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      compile 'com.android.support:appcompat-v7:21.0.0'
      compile 'com.nineoldandroids:library:2.4.0'
      compile 'com.android.support:support-v4:21.0.0'
      compile 'com.android.support:support-v4:21.0.0'
      compile files('C:/Users/Corey/.AndroidStudioBeta/Projects/AudioTimeShift/libraries/mpandroidchartlibrary-1-7-4.jar')
  }
  </code></pre>
  
  <p>As far as I can see, this should all be fine, however it is not working.
  This is the log from the Gradle console:</p>
  
  <pre><code>:app:preBuild
  :app:compileDebugNdk UP-TO-DATE
  :app:preDebugBuild
  :app:checkDebugManifest
  :app:preReleaseBuild
  :app:prepareComAndroidSupportAppcompatV72100Library UP-TO-DATE
  :app:prepareComAndroidSupportSupportV42100Library UP-TO-DATE
  :app:prepareDebugDependencies
  :app:compileDebugAidl UP-TO-DATE
  :app:compileDebugRenderscript UP-TO-DATE
  :app:generateDebugBuildConfig UP-TO-DATE
  :app:generateDebugAssets UP-TO-DATE
  :app:mergeDebugAssets UP-TO-DATE
  :app:generateDebugResValues UP-TO-DATE
  :app:generateDebugResources UP-TO-DATE
  :app:mergeDebugResources UP-TO-DATE
  :app:processDebugManifest UP-TO-DATE
  :app:processDebugResources UP-TO-DATE
  :app:generateDebugSources UP-TO-DATE
  :app:compileDebugJava
  Note: C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\src\main\java\com\bacon\corey\audiotimeshift\MainActivity.java uses or overrides a deprecated API.
  Note: Recompile with -Xlint:deprecation for details.
  Note: Some input files use unchecked or unsafe operations.
  Note: Recompile with -Xlint:unchecked for details.
  :app:preDexDebug
  :app:dexDebug
  UNEXPECTED TOP-LEVEL EXCEPTION:
  Error:Execution failed for task ':app:dexDebug'.
  &gt; com.android.ide.common.internal.LoggedErrorException: Failed to run command:
      C:\Program Files (x86)\Android\android-sdk\build-tools\21.0.2\dx.bat --dex --output C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\dex\debug C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\classes\debug C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\dependency-cache\debug C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\pre-dexed\debug\classes-08104da82547c1da8de562eb9350a514962ceaa7.jar C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\pre-dexed\debug\classes-c916341f097aba848a3f8d1cb524d87b40a5e434.jar C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\pre-dexed\debug\internal_impl-21.0.0-dd323fb38f6f05cc36bfccaf6824e44b4d16534e.jar C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\pre-dexed\debug\library-2.4.0-1028d824e09b12c83da4be3e497c82fdc33874f5.jar C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\pre-dexed\debug\mpandroidchartlibrary-1-7-4-1e0626ccaecee3e156334e8c3c9fcf07d352edb9.jar C:\Users\Corey\.AndroidStudioBeta\Projects\AudioTimeShift\app\build\intermediates\pre-dexed\debug\support-annotations-21.0.0-9528452d0a4563476596d64e06f21a3014c413f7.jar
  Error Code:
      2
  Output:
      UNEXPECTED TOP-LEVEL EXCEPTION:
      com.android.dex.DexException: Multiple dex files define Lcom/nineoldandroids/animation/ValueAnimator$AnimatorUpdateListener;
          at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:596)
          at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:554)
          at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:535)
          at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:171)
          at com.android.dx.merge.DexMerger.merge(DexMerger.java:189)
          at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:454)
          at com.android.dx.command.dexer.Main.runMonoDex(Main.java:302)
          at com.android.dx.command.dexer.Main.run(Main.java:245)
          at com.android.dx.command.dexer.Main.main(Main.java:214)
          at com.android.dx.command.Main.main(Main.java:106)
  Information:BUILD FAILED
  Information:Total time: 18.241 secs
  Information:1 error
  Information:0 warnings
  Information:See complete output in console
  </code></pre>
  
  <p>If someone could please give me a few pointers as to where I am going wrong, I would be immensively grateful.</p>
  
  <p>Thanks, Corey B :)</p>