How can I access a BuildConfig value in my AndroidManifest.xml file?

Replace

buildConfigField "long", "FACEBOOK_APP_ID", FACEBOOK_APP_ID

with

resValue "string", "FACEBOOK_APP_ID", FACEBOOK_APP_ID

then rebuild your project (Android Studio -> Build -> Rebuild Project).

The two commands both produce generated values - consisting of Java constants in the first case, and Android resources in the second - during project builds, but the second method will generate a string resource value that can be accessed using the @string/FACEBOOK_APP_ID syntax. This means it can be used in the manifest as well as in code.

note: when you use resValue the value can accidentally be overridden by the strings resource file (e.g. for another language)

To get a true constant value that you can use in the manifest and in java-code, use both manifestPlaceholders and buildConfigField: e.g.

android {
    defaultConfig {
        def addConstant = {constantName, constantValue ->
            manifestPlaceholders += [ (constantName):constantValue]
            buildConfigField "String", "${constantName}", "\"${constantValue}\""
        }

        addConstant("FACEBOOK_APP_ID", "xxxxx")
    }

access in the manifest file:

<meta-data android:name="com.facebook.sdk.ApplicationId" android:value="${FACEBOOK_APP_ID}"/>

from java:

BuildConfig.FACEBOOK_APP_ID

If the constant value needs to be buildType-specific, the helper addConstant needs to be tweaked (to work with groovy closure semantics), e.g.,

buildTypes {
    def addConstantTo = {target, constantName, constantValue ->
        target.manifestPlaceholders += [ (constantName):constantValue]
        target.buildConfigField "String", "${constantName}", "\"${constantValue}\""
    }
    debug {
        addConstantTo(owner,"FACEBOOK_APP_ID", "xxxxx-debug")
    }
    release {
        addConstantTo(owner,"FACEBOOK_APP_ID", "xxxxx-release")
    }

Another way to access Gradle Build Config values from your AndroidManifest.xml is through placeholders like this:

android {
    defaultConfig {
        manifestPlaceholders = [ facebookAppId:"someId..."]
    }
    productFlavors {
        flavor1 {
        }
        flavor2 {
            manifestPlaceholders = [ facebookAppId:"anotherId..." ]
        }
    }
}

and then in your manifest:

<meta-data android:name="com.facebook.sdk.ApplicationId" android:value="${facebookAppId}"/> 

See more details here: https://developer.android.com/studio/build/manifest-build-variables.html

(Old link just for reference: http://tools.android.com/tech-docs/new-build-system/user-guide/manifest-merger)

Access build.gradle properties in your manifest as in following example:

For example you have a property "applicationId" in your build.gradle and you want to access that in your AndroidManifest:

Access "applicationId" in AndroidManifest:

<receiver
        android:name="com.google.android.gms.gcm.GcmReceiver"
        android:exported="true"
        android:permission="com.google.android.c2dm.permission.SEND">
        <intent-filter>
            <action android:name="com.google.android.c2dm.intent.RECEIVE" />
            <category android:name="${applicationId}" />
        </intent-filter>
    </receiver>

Similarly, we can create string resources for other constants and access them in code files as simple as:

context.getString(R.string.GCM_SENDER_ID);