错误信息：

Error: Program type already present: com.google.zxing.BarcodeFormat

Caused by: java.lang.RuntimeException: com.android.builder.dexing.DexArchiveMergerException: Error while merging dex archives: H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\0.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\1.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\2.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\3.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\4.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\5.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\6.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\7.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\8.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\9.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\10.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\11.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\12.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\13.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\14.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\15.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\16.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\17.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\18.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\19.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\20.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\21.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\22.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\23.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\24.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\25.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\26.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\27.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\28.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\29.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\30.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\31.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\32.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\33.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\34.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\35.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\36.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\37.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\38.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\39.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\40.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\41.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\42.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\43.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\44.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\45.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\46.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\47.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\48.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\49.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\50.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\51.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\52.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\53.jar
Program type already present: com.google.zxing.BarcodeFormat
Learn how to resolve the issue at https://developer.android.com/studio/build/dependencies#duplicate_classes.
	at com.android.builder.profile.Recorder$Block.handleException(Recorder.java:55)
	at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:104)
	at com.android.build.gradle.internal.pipeline.TransformTask.transform(TransformTask.java:230)
	at sun.reflect.GeneratedMethodAccessor684.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:73)
	at org.gradle.api.internal.project.taskfactory.IncrementalTaskAction.doExecute(IncrementalTaskAction.java:50)
	at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:39)
	at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:26)
	at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$1.run(ExecuteActionsTaskExecuter.java:124)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)
	at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:113)
	at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:95)
	... 108 more
Caused by: com.android.builder.dexing.DexArchiveMergerException: Error while merging dex archives: H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\0.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\1.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\2.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\3.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\4.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\5.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\6.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\7.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\8.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\9.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\10.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\11.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\12.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\13.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\14.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\15.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\16.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\17.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\18.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\19.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\20.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\21.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\22.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\23.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\24.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\25.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\26.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\27.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\28.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\29.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\30.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\31.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\32.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\33.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\34.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\35.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\36.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\37.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\38.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\39.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\40.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\41.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\42.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\43.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\44.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\45.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\46.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\47.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\48.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\49.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\50.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\51.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\52.jar, H:\AndroidstudioProjects\LovePet\app\build\intermediates\transforms\dexBuilder\debug\53.jar
Program type already present: com.google.zxing.BarcodeFormat
Learn how to resolve the issue at https://developer.android.com/studio/build/dependencies#duplicate_classes.
	at com.android.builder.dexing.D8DexArchiveMerger.getExceptionToRethrow(D8DexArchiveMerger.java:132)
	at com.android.builder.dexing.D8DexArchiveMerger.mergeDexArchives(D8DexArchiveMerger.java:117)
	at com.android.build.gradle.internal.transforms.DexMergerTransformCallable.call(DexMergerTransformCallable.java:101)
	at com.android.build.gradle.internal.transforms.ExternalLibsMergerTransform.transform(ExternalLibsMergerTransform.kt:122)
	at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:239)
	at com.android.build.gradle.internal.pipeline.TransformTask$2.call(TransformTask.java:235)
	at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:102)
	... 123 more
Caused by: com.android.tools.r8.CompilationFailedException: Compilation failed to complete
	at com.android.tools.r8.utils.ExceptionUtils.withCompilationHandler(ExceptionUtils.java:65)
	at com.android.tools.r8.utils.ExceptionUtils.withD8CompilationHandler(ExceptionUtils.java:43)
	at com.android.tools.r8.D8.run(D8.java:90)
	at com.android.builder.dexing.D8DexArchiveMerger.mergeDexArchives(D8DexArchiveMerger.java:115)
	... 128 more
Caused by: com.android.tools.r8.utils.AbortException: Error: Program type already present: com.google.zxing.BarcodeFormat
	at com.android.tools.r8.utils.Reporter.failIfPendingErrors(Reporter.java:116)
	at com.android.tools.r8.utils.Reporter.fatalError(Reporter.java:74)
	at com.android.tools.r8.utils.ExceptionUtils.withCompilationHandler(ExceptionUtils.java:59)
	... 131 more

解决方式：

  Multiple dex files define Lcom/google/zxing/BarcodeFormat

Error: Program type already present: com.google.zxing.BarcodeFormat，这段是说你的zxing库出现问题，一般Unable to execute dex是由于重复包导入造成的，zxing库这个概念我并不清楚，这里感谢下一个非常腻害的程序员，微博名@李正阳，他给我指导这个zxing库。

     在你的libs文件夹下，一定有一个重复的包，不是重名，（我刚开始以为重复的包就是重名）我这里是两个core包，一个是core.jar，一个是core.3.1.0.jar，这两个都是zxing库的，删除其中一个，再clean，不行的话删除另一个。

          很早的时候我以为是buildpath里面的引入重复了。我把order and export里的Android private libary和Android Dpendencies这两个包去掉，居然编译成功了，但是运行是闪退的，这是个非常大的误区，虽然我并不知道为什么会出现这样的情况，希望大神看到我的文章，能给我解答下。

        另外，出现Unable to execute dex，也可能是你的依赖包出现问题，在引入项目的时候细心。