I tried all the above and none of them helps. finally, I find this work for me:

app/build.gradle:

android {
    defaultConfig {
       multiDexEnabled true
    }
}

I had the same problem when I update from com.google.android.gms:play-services:11.2.2 to com.google.android.gms:play-services:11.4.0. This solved it for me:

1. clean
2. rebuild

Pay attention to Warnings!

Sometimes you only need to eliminate warnings and the error will be disappeared automatically. See below special case:

I had these two dependencies in my module-level build.gradle file:

implementation 'com.android.support:appcompat-v7:27.0.2'
implementation 'com.android.support:recyclerview-v7:27.0.2'

and Studio had warned (in addition to dex merging problem):

All com.android.support libraries must use the exact same version specification (mixing versions can lead to runtime crashes). Found versions 27.0.2, 21.0.3. Examples include com.android.support:animated-vector-drawable:27.0.2 and com.android.support:support-v4:21.0.3

So I explicitly determined the version of com.android.support:support-v4 (see here for details) and both problems (the warning and the one related to dex merging) solved:

implementation 'com.android.support:support-v4:27.0.2'  // Added this line (according to above warning message)
implementation 'com.android.support:appcompat-v7:27.0.2'
implementation 'com.android.support:recyclerview-v7:27.0.2'

^{See below comments for other similar situations.}

In my case, Unfortunately, neither Michel's nor Suragch's solutions worked for me.

So I solved this issue by doing the following:

In gradle:3.0 the compile configuration is now deprecated and should be replaced by implementation or api. For more information you can read here You can read the official docs at Gradle Build Tool

The compile configuration still exists but should not be used as it will not offer the guarantees that the api and implementation configurations provide.

it's better to use implementation or api rather compile

just replace compile with implementation, debugCompile with debugImplementation, testCompile with testImplementation and androidtestcompile with androidTestImplementation

For example: Instead of this

compile 'com.android.support:appcompat-v7:26.0.2'
compile 'com.android.support:support-v4:26.1.0'
compile 'com.github.bumptech.glide:glide:4.0.0'

use like this

implementation 'com.android.support:appcompat-v7:26.0.2'
implementation 'com.android.support:support-v4:26.1.0'
implementation 'com.github.bumptech.glide:glide:4.0.0'

After that

• Delete the .gradle folder inside your project ( Note that, in order to see .gradle, you need to switch to the "Project" view in the navigator on the top left )
• Delete all the build folders and the gradle cache.
• From the Build menu, press the Clean Project button.
• After task completed, press the Rebuild Project button from the Build menu.

Hope it will helps !

if(1. Try to clean and rebuild work ) then good

else if (2. Try to remove gradle work ) then good

else-> 3. Try to add in grade.properties

android.enableD8 = false

Edit 2021: This 3rd option is deprecated now, use the other options

else-> 4. Add multiDexEnabled true to your build.gradle

android {
    compileSdkVersion 26
    defaultConfig {
      ...
        minSdkVersion 15
        targetSdkVersion 26
        multiDexEnabled true
     ...
    }
}

and add the dependency

dependencies {
    compile 'com.android.support:multidex:1.0.1'}

It may the first one works for u and so on but it really depends on the nature of your problem for me for example

I got the error once I have added this library

implementation 'com.jjoe64:graphview:4.2.2'

and later I discovered that I have to check that and I have to add the same version of the support libraries. So I have to try another version

compile 'com.jjoe64:graphview:4.2.1'

and it fixes the problem. So pay attention for that.

Hi I have same issue tried almost everything. So, finally i resolved after 6 hour long struggle by debugging everything line by line.

classpath 'com.google.gms:google-services:3.0.0'

Google-services 3.0 Doesn't support firebase with Studio 3.0 with playServiceVersion: 11.6.0 or less.

implementation "com.google.firebase:firebase-messaging:$rootProject.ext.playServiceVersion"
implementation "com.google.firebase:firebase-core:$rootProject.ext.playServiceVersion"
implementation "com.firebase:firebase-jobdispatcher-with-gcm-dep:$rootProject.ext.jobdispatcherVersion"

Solution :

I have change google services to

classpath 'com.google.gms:google-services:3.1.1'

And it support firebase services.

Hopefully somebody save his/her time.

1. Enable

   defaultConfig { multiDexEnabled true }

2. If step 1 doesn't work then

   Go to project structure and find out the external library which is using a different version. Double click on it and delete its jar file. Close the project and open again android studio will rebuild the project. The problem should be gone.

If this error appeared for you after including kotlin support, and none of the other solutions work, try changing the kotlin dependency of app module's build.gradle to:

implementation ("org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version") {
    exclude group: 'org.jetbrains', module: 'annotations'
}

This works for me on Android Studio 3.0 Beta 6. See this answer for further explanation.

With Android Studio 3.0 stable build Below steps worked for me:

1. Got to SdkManager-->Android Sdk --> Sdk Tools and Update Google play services to latest version to 46.
2. Clean project and rebuild project.

add commands below:

android {
...

    dexOptions {

        jumboMode true
        javaMaxHeapSize "4g"

    }
}

I agree with Chris-Jr. If you are using Firebase to embed your AdMob ads (or even if you are not) the play-services-analytics includes the play-services-ads even though you don't add that as a dependency. Google have obviously made a mistake in their 11.4.0 roll-out as the analytics is including version 10.0.1 of ads, not 11.4.0 (the mouse over hint in the gradle shows this).

I manually added compile 'com.google.android.gms:play-services-ads:11.4.0' at the top which worked, but only after I disabled Instant Run: http://stackoverflow.com/a/35169716/530047

So its either regress to 10.0.1 or add the ads and disable Instant Run. That's what I found if it helps any.

I encountered the same problem and found the real reason for my case. Previously, I also tried all the previous answers again, but it did not solve the problem. I have two module in my wear app project, and the build.gradle as follows：

wear module's build.gradle:

implementation project(':common')
implementation files('libs/farmer-motion-1.0.jar')

common module's build.gradle:

implementation files('libs/farmer-motion-1.0.jar')

Before upgrade to gradle 3.x, 'implementation' are all 'compile'.

I run gradlew with --stacktrace option to get the stack trace, you can just click this on gradle console window when this problem arises. And found that dependency to the jar package repeated:

Caused by: com.android.dex.DexException: Multiple dex files define Lcom/farmer/motion/common/data/pojo/SportSummary$2;

Class SportSummary in the farmer-motion-1.0.jar package, after read the official migration guide, i changed my build.gradle to follows:

wear module's build.gradle:

implementation project(':common')
// delete dependency implementation files('libs/farmer-motion-1.0.jar')

common module的build.gradle:

api files('libs/farmer-motion-1.0.jar') // change implementation to api

Now wear module will has the dependency of farmer-motion-1.0.jar export by common module. If there has no dependency on jar package during runtime, 'implementation' dependency of jar package can also be change to 'compileOnly'.

This may not be your problem, but I got this error when I accidentally included two identical (but differently named) libraries in the dependencies{} section of the project.

For me it was updating the firebase messaging in app\build.gradle:

compile 'com.google.firebase:firebase-messaging:10.0.1'

to

compile 'com.google.firebase:firebase-messaging:11.4.2'

One of possible root causes: duplicate transient dependencies that weren't properly handled by Android Studio import of multi-module projects. Check your list and remove them. For me, the fix was literally this:

--- a/project/module/build.gradle
+++ b/project/module/build.gradle
@@ -21,5 +21,4 @@ android {
 dependencies {
     implementation project(':upstream-dependency-project')
     implementation 'com.android.support:support-v4:18.0.0'
-    implementation files('libs/slf4j-android-1.6.1-RC1.jar')
 }

I find out the reason of this problem for my project. I was added one dependency twice in build.gradle. One time by adding dependency and one time again by adding jar dependency:

compile 'org.achartengine:achartengine:1.2.0'
...
implementation files('../achartengine-1.2.0.jar')

after remove the first line problem solved.

In my case a library makes this problem, library was successfully added to project but when i run my app it shows me this error. So if this happens to you too, you can go to github and check issues or raise new issue. If you do not find any solution regarding the library i suggest you to replace it.

I had same problem. I just enabled Instant Run(It was disabled) then my project worked. You can find it in-

File->Settings-> Build,Execution,Deployment->Instant Run

In Android studio 3.5 Instant Run have been removed. Please see here for reference

Unfortunately, neither Michel's nor Suragch's solutions worked for me.

What I eventually had to do was simply rollback my com.google.firebase:firebase-database to version 10.0.1, since 11.4.0 was causing a dependency inconsistency warning in my app gradle file.

In my case, I import one 'android_support' lib twice ,so I delete one under 'libs' directory and rebuild.

    android {
        defaultConfig {
            multiDexEnabled true
            }
    }

   compile 'com.google.android.gms:play-services:11.0.4'

   compile 'com.google.android.gms:play-services-location:11.0.4'

build clean and build Rebuild

After upgrading some dependency I found solutions. We should use latest play service version. In build.gradle[app] dependency.

compile 'com.android.support:multidex:1.0.2'
compile 'com.google.android.gms:play-services:11.8.0'
compile 'com.google.firebase:firebase-core:11.8.0'

In build.gradle[project], we should use latest Google plug-in.

classpath 'com.google.gms:google-services:3.1.1'

I am also sharing below code for better understanding.

    android {
    compileSdkVersion 26
    buildToolsVersion '26.0.2'
    defaultConfig {
        applicationId "com.***.user"
        minSdkVersion 17
        targetSdkVersion 26
        versionCode 26
        versionName "1.0.20"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        multiDexEnabled true
        vectorDrawables.useSupportLibrary = true

        aaptOptions {
            cruncherEnabled = false
        }

    }
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

For me the issue was that 2 of the jars that I included in the project had the same classes in them.

For 1 of these jars I needed to exclude the classes:

jar {
    exclude('com/files/to/exclude/**')
}

In my case the error was importing the dependency:

implementation 'com.firebaseui:firebase-ui:2.3.0'

and I was not using it, it started working when I deleted it cleaned project and recomplied. Of course I also did what the people above did which was:

• Changing complie to implementation throughout the whole app.grade
• Changing testcomplie to testimplementation throughout the whole app.grade
• Make sure I have multidexenabled true
• Update compileSdk to 26
• Deleted .gradle file (found in project), clean project and recompile

and finally...

• Deleted implementation 'com.firebaseui:firebase-ui:2.3.0' (Since I was not using it in my code)

Change you buildToolsVersion to some other version and sync, change it back and sync again. It will work again.

If you are using Firebsae in your plugin, this issue will come due to play services version issue, try this `cordov

cordova.system.library.4=com.google.gms:google-services:3.3.0
    cordova.system.library.5=com.google.android.gms:play-services-tagmanager:+
    cordova.system.library.6=com.google.firebase:firebase-core:16.0.1
    cordova.system.library.7=com.google.firebase:firebase-messaging:17.1.0
    cordova.system.library.8=com.google.firebase:firebase-crash:16.0.1
    cordova.system.library.9=com.google.firebase:firebase-config:16.0.0
    cordova.system.library.10=com.google.firebase:firebase-perf:16.0.0 

Change your project.properties like this, then this issue will be resolved Reference

This works for me-

Add code at last in platforms\android\build.gradle

configurations.all { 
 resolutionStrategy{
    force 'com.android.support:support-v4:26.0.0'
    }

    resolutionStrategy.eachDependency { DependencyResolveDetails details ->
    def requested = details.requested
    if (requested.group == 'com.android.support') {
       if (!requested.name.startsWith("multidex")) {
      details.useVersion '26.0.0'
     }
   }
  }
}

add this in your app/build.gradle. It will work

implementation 'com.android.support:design:27.1.0'

Just add below in build.gradle,

defaultConfig { multiDexEnabled true }

This hasn't been shared here yet so hopefully it can help someone.

Following this link solved the same issue for me.

To begin, I'll note that I did not have to set multiDexEnabled to true.

First I set dependencies in my pubspec.yaml to

dependencies:
  flutter:
    sdk: flutter
  cloud_firestore: ^0.8.2 

and ran flutter packages get in my IDE's terminal.

Also I had to change the minimum target SDK version:

1. Open android/app/build.gradle, then find the line that says minSdkVersion 16.
2. Change that line to minSdkVersion 21.
3. Save the file.

This alone may fix your problem; however I had to also do the following because some of my dependency versions were mismatched.

I had to open android/app/build.gradle, then add the following line as the last line in the file: apply plugin: 'com.google.gms.google-services'

Next, I had to open android/build.gradle, then inside the buildscript tag, add a new dependency:

buildscript {
   repositories {
       // ...
   }

   dependencies {
       // ...
       classpath 'com.google.gms:google-services:3.2.1'   // new
   }
}

After this my app finally ran on the android emulator.

The link has a more complete walkthrough if you get stuck.

Also, to note, I did not have to set multiDexEnabled to true.

In my case the following works

implementation 'com.google.android.gms:play-services-ads:17.2.0'
implementation 'com.google.firebase:firebase-core:16.0.9'
implementation 'com.google.firebase:firebase-analytics:16.5.0'
implementation 'com.google.firebase:firebase-messaging:18.0.0'

In my app module. The problem was they firebase-analytics latest library, it is not working properly with the other latest libraries.

Just add this line in app/build.gradle

defaultConfig {
       multiDexEnabled true 
    }

Go Unity >> Edit Project settings>>player, look for Minify section and then choose the Proguard option

Along with Unable to merge dex I had an error java.lang.OutOfMemoryError: Java heap space when building a project.

In the gradle.properties file I had this commented line:

# org.gradle.jvmargs=-Xmx2048m -XX:MaxPermSize=512m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8

Uncommenting this line and increasing the heap memory to 3g solved the problem:

org.gradle.jvmargs=-Xmx3g -XX:MaxPermSize=512m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8

Tried all of them before focusing on dependencies.

The below where killers:

//implementation 'org.apache.httpcomponents:httpcore:4.3.1'
//implementation 'org.apache.httpcomponents:httpmime:4.3.1'

Now is working as intended.

If you are using

compile ("org.apache.oltu.oauth2:org.apache.oltu.oauth2.client:1.0.1")

you should change it to

compile ("org.apache.oltu.oauth2:org.apache.oltu.oauth2.client:1.0.1"){
    exclude group:'org.apache.oltu.oauth2' , module: 'org.apache.oltu.oauth2.common'
}

As the client lib already contains the common lib it creates a duplicate class entry which gives an error:

Unable to merge dex