Separate Crashlytics reporting for debug and release buildTypes using a Gradle build

build.gradle

// The following code allows an app to report Crashlytics crashes separately 
// for release and debug buildTypes when using Gradle. This code should be inserted 
// into the specified locations within your build.gradle (Module:app) file
    
    // The buildTypes { } block should be inserted inside the android { } block
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            ext.crashlyticsApiSecret = "release api secret"
            ext.crashlyticsApiKey = "release api key"
        }
        debug {
            ext.crashlyticsApiSecret = "debug api secret"
            ext.crashlyticsApiKey = "debug api key"
        }
    }

// The following code can be inserted at the bottom of your build.gradle file
import com.crashlytics.tools.utils.PropertiesUtils

File crashlyticsProperties = new File("${project.projectDir.absolutePath}/fabric.properties")
android.applicationVariants.all { variant ->
    def variantSuffix = variant.name.capitalize()
    def generateResourcesTask = project.tasks.getByName("fabricGenerateResources${variantSuffix}")
    def generatePropertiesTask = task("fabricGenerateProperties${variantSuffix}") << {
        Properties properties = new Properties()
        println "...copying apiSecret for ${variant.name}"
        properties.put("apiSecret", variant.buildType.ext.crashlyticsApiSecret)
        println "...copying apiKey for ${variant.name}"
        properties.put("apiKey", variant.buildType.ext.crashlyticsApiKey)
        PropertiesUtils.injectPropertyInFile(crashlyticsProperties, properties, "")
    }
    generateResourcesTask.dependsOn generatePropertiesTask
}

If you get an error like could not find method leftshift() after applying the above thing then.
Replace leftshift(<<) with doLast.

import com.crashlytics.tools.utils.PropertiesUtils

File crashlyticsProperties = new File("${project.projectDir.absolutePath}/fabric.properties")
android.applicationVariants.all { variant ->
    def variantSuffix = variant.name.capitalize()
    def generateResourcesTask = project.tasks.getByName("fabricGenerateResources${variantSuffix}")
    def generatePropertiesTask = task("fabricGenerateProperties${variantSuffix}") doLast {
        Properties properties = new Properties()
        println "...copying apiSecret for ${variant.name}"
        properties.put("apiSecret", variant.buildType.ext.crashlyticsApiSecret)
        println "...copying apiKey for ${variant.name}"
        properties.put("apiKey", variant.buildType.ext.crashlyticsApiKey)
        PropertiesUtils.injectPropertyInFile(crashlyticsProperties, properties, "")
    }
    generateResourcesTask.dependsOn generatePropertiesTask
}