MultiDexApplication not recognized

Trying to use MultiDexApplication in my app, but the class is not recognized when I try to extend my application activity with it.

Here is my build.gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion '21.0.1'
    defaultConfig {
        applicationId 'com.myapp'
        minSdkVersion 10
        targetSdkVersion 21
        versionCode 115
        versionName '4.8'
    }

    buildTypes {
        debug {
            debuggable true
            runProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
        release {
            debuggable false
            runProguard true
            zipAlign true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    packagingOptions {
        exclude 'META-INF/LICENSE.txt'
        exclude 'META-INF/NOTICE.txt'
    }

    lintOptions {
        checkReleaseBuilds false
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])

    compile 'com.google.android.gms:play-services:6.1.11'

    compile 'com.android.support:appcompat-v7:21.0.0'

    compile 'com.nineoldandroids:library:2.4.0'
    compile 'com.viewpagerindicator:library:2.4.1@aar'
    compile project(':facebook')
}

You can see that I'm compiling on 21, using the latest build tools, and the latest google play services and support library.

Has anyone gotten this to work?

MultiDexApplication class is not part of appcompat-v7 library. It is being shipped in a separate jar (called android-support-multidex).

Find the android-support-multidex.jar under /sdk/extras/android/support/multidex/library/libs (available from revision 21 of support library) and copy it to your project's libs folder.

Update (11/5/2014):
The jar is now available in central repository:

dependencies {
  ...
  compile 'com.android.support:multidex:1.0.0'
}

For more info, see here.

Update (27/9/2021):
Jetpack (AndroidX) users should add this as a dependency:

dependencies {
  ...
  implementation 'androidx.multidex:multidex:2.0.1'
}