Restructure docs for KTX (#314)

Author: samtstern

.opensource/project.json

@@ -4,13 +4,23 @@
     "platforms": [
         "Android"
     ],
-    "content": "README.md",
-    "pages": [
-        "firebase-common/README.md",
-        "firebase-firestore/README.md",
-        "protolite-well-known-types/README.md"
-    ],
+    "content": "docs/README.md",
+    "pages": {
+        "README.md": "Development Guide",
+        "docs/ktx/common.md": "Common KTX",
+        "docs/ktx/firestore.md": "Firestore KTX"
+    },
     "related": [
         "firebase/quickstart-android"
+    ],
+    "tabs": [
+        {
+            "title": "Main Reference",
+            "href": "https://firebase.google.com/docs/reference/android/"
+        },
+        {
+            "title": "KTX Reference",
+            "href": "https://firebase.github.io/firebase-android-sdk/reference/kotlin/firebase-ktx/"
+        }
     ]
 }

docs/README.md

@@ -0,0 +1,30 @@
+# Firebase Android SDK
+
+The Firebase SDK for Android is the official way to add Firebase to your
+Android app. To get started, visit the [setup instructions][android-setup].
+
+## Open Source
+
+This repository includes the following Firebase SDKs for Android:
+
+  * `firebase-common`
+  * `firebase-database`
+  * `firebase-firestore`
+  * `firebase-functions`
+  * `firebase-inappmessaging-display`
+  * `firebase-storage`
+
+For more information on building the SDKs from source or contributing,
+visit the [main README][main-readme].
+
+## Kotlin Extensions
+
+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
+[main-readme]: https://github.com/firebase/firebase-android-sdk/blob/master/README.md

docs/ktx/common.md

@@ -0,0 +1,42 @@
+# Firebase Common Kotlin Extensions
+
+## Getting Started
+
+To use the Firebase Common Android SDK with Kotlin Extensions, 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

@@ -0,0 +1,70 @@
+# Firestore Kotlin Extensions
+
+## Getting Started
+
+To use the Cloud Firestore Android SDK with Kotlin Extensions, 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-firestore library
+implementation 'com.google.firebase:firebase-firestore-ktx:$VERSION'
+```
+
+## Features
+
+### Get an instance of FirebaseFirestore
+
+**Kotlin**
+```kotlin
+val firestore = FirebaseFirestore.getInstance()
+val anotherFirestore = FirebaseFirestore.getInstance(FirebaseApp.getInstance("myApp"))
+```
+
+**Kotlin + KTX**
+```kotlin
+val firestore = Firebase.firestore
+val anotherFirestore = Firebase.firestore(Firebase.app("myApp"))
+```
+
+### Convert a DocumentSnapshot field to a POJO
+
+**Kotlin**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.get("fieldPath", MyClass::class.java)
+```
+
+**Kotlin + KTX**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.get<MyClass>("fieldPath")
+```
+
+### Convert a DocumentSnapshot to a POJO
+
+**Kotlin**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.toObject(MyClass::class.java)
+```
+
+**Kotlin + KTX**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.toObject<MyClass>()
+```
+
+### Convert a QuerySnapshot to a list of POJOs
+
+**Kotlin**
+```kotlin
+val snapshot: QuerySnapshot = ...
+val objectList = snapshot.toObjects(MyClass::class.java)
+```
+
+**Kotlin + KTX**
+```kotlin
+val snapshot: QuerySnapshot = ...
+val objectList = snapshot.toObjects<MyClass>()
+```