org.gradle.api.tasks.TaskExecutionException: Execution failed for task ‘:app:transformClassesWithDexForDebug’

Check build.gradle(Module: Android) fixed problem for me.

Modify it to workable version.

android {
    buildToolsVersion '23.0.1'
}

Just a simple solution is here…it worked for me:

1. Clean Project
2. Rebuild project
3. Sync project with gradle file

the steps I followed are:

1. close Android Studio (or IntelliJ IDEA)
2. in your project’s directory:
   1. delete .idea directory
   2. delete .gradle directory
   3. delete all .iml files
      • find . | grep -e .iml$ | xargs rm
3. use Android Studio to re-open the directory as a project

Terminal commands:

# close Android Studio
cd "your project's directory"
rm -rf ./.idea
rm -rf ./.gradle
find . | grep -e .iml$ | xargs rm
# use Android Studio to re-open the directory as a project

I had the same issue and I could solve it like this:

1) If your minSdkVersion is set to 21 or a higher value, the only thing you need to do is to set multiDexEnabled in your build.gradle file at the module level, as shown below:

android {
    defaultConfig {
        ...
        minSdkVersion 21 
        targetSdkVersion 28
        multiDexEnabled true
    }
    ...
}

2) However, if your minSdkVersion is set to 20 or less, you should use the MultiDex compatibility library, as follows:

2.1) Modify the module-level build.gradle file to enable MultiDex and add the MultiDex library as dependency, as shown below

android {
    defaultConfig {
        ...
        minSdkVersion 15 
        targetSdkVersion 28
        multiDexEnabled true
    }
    ...
}

dependencies {
  implementation 'com.android.support:multidex:1.0.3'
}

2.2) According to the Application class or not, do one of the following actions:

2.2.1) If you do not cancel the Application class, modify your manifest file to set android: name in the <application> tag as shown below:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myapp">
    <application
            android:name="android.support.multidex.MultiDexApplication" >
        ...
    </application>
</manifest>

2.2.2) If you cancel the Application class, you must change it to extend MultiDexApplication (if possible) as shown below:

public class MyApplication extends MultiDexApplication { ... }

2.2.3) Also, if you override the Application class and can not change the base class, alternatively you can override the attachBaseContext () method and invoke MultiDex.install (this) to enable MultiDex:

public class MyApplication extends SomeOtherApplication {
  @Override
  protected void attachBaseContext(Context base) {
     super.attachBaseContext(base);
     MultiDex.install(this);
  }
}

Please use this link, it was really useful for me!