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