Multiple dex files define Landroid/support/v4/accessibilityservice/AccessibilityServiceInfoCompat

Run gradle -q dependencies (or gradle -q :projectName:dependencies) to generate a dependency report. You should see where r7 is coming from, such as:

compile - Classpath for compiling the main sources.
+--- com.commonsware.cwac:camera-v9:0.5.4
|    +--- com.actionbarsherlock:actionbarsherlock:4.4.0
|    |    \--- com.google.android:support-v4:r7
|    +--- com.commonsware.cwac:camera:0.5.4
|    \--- com.android.support:support-v4:18.0.+ -> 18.0.0
\--- com.android.support:support-v4:18.0.+ -> 18.0.0

Then, use the exclude directive to block that dependency. In my case, it is coming from my CWAC-Camera library, and so I use:

dependencies {
    compile('com.commonsware.cwac:camera-v9:0.5.4') {
      exclude module: 'support-v4'
    }

    compile 'com.android.support:support-v4:18.0.+'
}

(where the second compile statement indicates what version you actually want)

That should clear matters up, as you will see if you run the dependency report again:

compile - Classpath for compiling the main sources.
+--- com.commonsware.cwac:camera-v9:0.5.4
|    +--- com.actionbarsherlock:actionbarsherlock:4.4.0
|    \--- com.commonsware.cwac:camera:0.5.4
\--- com.android.support:support-v4:18.0.+ -> 18.0.0

I solved similar error by adding following piece of code to my build.gradle file inside the android block.

android {
    dexOptions {
        preDexLibraries = false
    }
}

Since A picture is worth a thousand words

To make it easier and faster to get this task done with beginners like me. this is the screenshots that shows the answer posted by @edsappfactory.com that worked for me:

First open the Gradle view on the right side of Androidstudio, in your app's item go to Tasks then Android then right-click androidDependencies then choose Run:

Second you will see something like this :

The main reason i posted this that it was not easy to know where to execute a gradle task or the commands posted above. So this is where to excute them as well.

SO, to execute gradle command:

First:

Second:

Easy as it is.

Thats it.

Thank you.

Also to note you can see your android dependencies, by going to your Android Studio Gradle view, and selecting the target "androidDependencies".

One more tip: I was having this issue, until I removed the v4 support lib from the libs folder in both the project and my related module/library project(s).

I started getting this error when upgrading to ButterKnife 8.5.1. None of the other answers here worked for me.

I used gradle -q :app:dependencies to see the tree, and then looked through jar files until I found the conflict. The conflict was that butterknife's dependency on com.android.support:support-compat:25.1.0 contains a version of the accessibility class, and com.android.support:support-v4:23.1.1 also contains the class.

I solved it by changing my dependency from this:

compile 'com.jakewharton:butterknife:8.5.1'

to this:

compile('com.jakewharton:butterknife:8.5.1') {
    exclude module: 'support-compat'
}

It doesn't seem to affect ButterKnife's operation so far.

Edit: There is a better solution, which was to upgrade my android support libraries to match ButterKnife's:

compile('com.android.support:appcompat-v7:25.2.0')
compile('com.android.support:design:25.2.0')
compile 'com.jakewharton:butterknife:8.5.1'