Update docs, add kotlin

Author: samtstern

.opensource/project.json

@@ -7,6 +7,7 @@
     "content": "docs/README.md",
     "pages": {
         "README.md": "Development Guide",
+        "docs/ktx/common.md": "Common KTX",
         "docs/ktx/firestore.md": "Firestore KTX"
     },
     "related": [

docs/README.md

@@ -24,6 +24,7 @@ The following Firebase SDKs for Android have Kotlin extension libraries
 that allow you to write more idiomatic Kotlin code when using Firebase
 in your app:
 
+  * [`firebase-common`](./ktx/common.md)
   * [`firebase-firestore`](./ktx/firestore.md)
 
 [android-setup]: https://firebase.google.com/docs/android/setup

docs/ktx/common.md

@@ -0,0 +1,42 @@
+# Firebase Common Kotlin Extensions
+
+## Getting Started
+
+To use the Firebase Common Android SDK with Kotlin Extenstions, add the following
+to your app's `build.gradle` file:
+
+```groovy
+// See maven.google.com for the latest versions
+// This library transitively includes the firebase-common library
+implementation 'com.google.firebase:firebase-common-ktx:$VERSION'
+```
+
+## Features
+
+### Get the default FirebaseApp and FirebaseOptions
+
+**Kotlin**
+```kotlin
+val defaultApp = FirebaseApp.getInstance()
+val defaultOptions = defaultApp.options
+```
+
+**Kotlin + KTX**
+```kotlin
+val defaultApp = Firebase.app
+val defaultOptions = Firebase.options
+```
+
+### Initialize a FirebaseApp
+
+**Kotlin**
+```kotlin
+val options = FirebaseApp.getInstance().options
+val anotherApp = FirebaseApp.initializeApp(context, options, "myApp")
+```
+
+**Kotlin + KTX**
+```kotlin
+var anotherApp = Firebase.initialize(context, Firebase.options, "myApp")
+```
+

docs/ktx/firestore.md

@@ -6,36 +6,39 @@ To use the Cloud Firestore Android SDK with Kotlin Extenstions, add the followin
 to your app's `build.gradle` file:
 
 ```groovy
-// This library transitively includes the Firestore Android SDK
-implementation 'com.google.firebase:firebase-firestore-ktx:18.1.0
+// See maven.google.com for the latest versions
+// This library transitively includes the firebase-firestore library
+implementation 'com.google.firebase:firebase-firestore-ktx:$VERSION'
 ```
 
 ## Features
 
-### Convert a DocumentSnapshot field to a POJO
+### Get an instance of FirebaseFirestore
 
 **Kotlin**
 ```kotlin
-val snapshot: DocumentSnapshot = ...
-val myObject = snapshot.get("fieldPath", MyClass::class.java)
+val firestore = FirebaseFirestore.getInstance()
+val anotherFirestore = FirebaseFirestore.getInstance(FirebaseApp.getInstance("myApp"))
 ```
 
 **Kotlin + KTX**
 ```kotlin
-val snapshot: DocumentSnapshot = ...
-val myObject = snapshot.get<MyClass>("fieldPath")
+val firestore = Firebase.firestore
+val anotherFirestore = Firebase.firestore(Firebase.app("myApp"))
 ```
 
-### Get an instance of FirebaseFirestore
+### Convert a DocumentSnapshot field to a POJO
 
 **Kotlin**
 ```kotlin
-val firestore = FirebaseFirestore.getInstance()
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.get("fieldPath", MyClass::class.java)
 ```
 
 **Kotlin + KTX**
 ```kotlin
-val firestore = Firebase.firestore
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.get<MyClass>("fieldPath")
 ```
 
 ### Convert a DocumentSnapshot to a POJO