Android 多个DEX错误 Multiple dex files define Landroid/support/v7/app/ActionBar$DisplayOptions;

今天在写程序的时候我的Android Studio 突然编译错误（错误提示如下：）后来经过我的几番折腾发现每一次都要先Clear Project一下然后再Build就可以了，如果你第二次再Build的时候就报错。后来我就找到了最强的老师（Google）尝试解决！可惜很遗憾，我在Google上看到的都是Eclipse上的解决方法。并没有找到我想要的答案，难道要我每一次在Build的时候都要先Clear Project吗？最后又经过我的几番折腾我发现在Project Structure--->app--->Properties中有一个选项叫：Incremental Dex (增加的DEX)的值为True,我又新建了一个项目发现默认值是空值，果然把这个改成空值问题就全然解决了！虽然现在我也不知道这一个选项到底是有什么用。

错误提示：

Information:Gradle tasks [:app:assembleDebug]
:app:preBuild UP-TO-DATE
:app:preDebugBuild UP-TO-DATE
:app:checkDebugManifest
:app:preReleaseBuild UP-TO-DATE
:app:prepareComAndroidSupportAnimatedVectorDrawable2330Library UP-TO-DATE
:app:prepareComAndroidSupportAppcompatV72330Library UP-TO-DATE
:app:prepareComAndroidSupportSupportV42330Library UP-TO-DATE
:app:prepareComAndroidSupportSupportVectorDrawable2330Library 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:processDebugJavaRes UP-TO-DATE
:app:compileDebugJavaWithJavac
:app:compileDebugNdk UP-TO-DATE
:app:compileDebugSources
:app:preDexDebug UP-TO-DATE
:app:dexDebug
UNEXPECTED TOP-LEVEL EXCEPTION:
com.android.dex.DexException: Multiple dex files define Landroid/support/v7/app/ActionBar$DisplayOptions;
    at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:591)
    at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:546)
    at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:528)
    at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:164)
    at com.android.dx.merge.DexMerger.merge(DexMerger.java:188)
    at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:504)
    at com.android.dx.command.dexer.Main.runMonoDex(Main.java:334)
    at com.android.dx.command.dexer.Main.run(Main.java:277)
    at com.android.dx.command.dexer.Main.main(Main.java:245)
    at com.android.dx.command.Main.main(Main.java:106)
Error:Execution failed for task ‘:app:dexDebug‘.
> com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process ‘command ‘C:\Program Files\Java\jdk1.8.0_73\bin\java.exe‘‘ finished with non-zero exit value 2

解决方法：