docs: add android target guide (#1129)

Co-authored-by: Kamil Berdychowski <[email protected]>

README.md

@@ -34,11 +34,14 @@ A current release is on the leading edge of our SDK development, and is intended
 Getting Started Docs: https://developer.box.com/guides/tooling/sdks/java/
 API Reference: https://developer.box.com/reference/
 
-## Quickstart
+## JVM
+
 The SDK can be obtained by adding it as a [maven dependency](http://opensource.box.com/box-java-sdk/),
 cloning the source into your project, or by downloading one of the precompiled JARs from the
 [releases page on GitHub](https://github.com/box/box-java-sdk/releases).
 
+If you are developing application for Android visit our [Android guide](doc/android.md)
+
 **IF YOU USE THE JAR, you'll also need to include several dependencies:**
 
 1. [minimal-json v0.9.5](https://github.com/ralfstx/minimal-json)
@@ -55,7 +58,10 @@ cloning the source into your project, or by downloading one of the precompiled J
    [Java Cryptography Extension for IBM JDK](https://www14.software.ibm.com/webapp/iwm/web/preLogin.do?source=jcesdk)
 
 An app has to be authorized by the admin of the enterprise before these tests. It's always good to begin with the
-[Getting Started Section](https://developer.box.com/docs/setting-up-a-jwt-app) at Box's developer website
+[Getting Started Section](https://developer.box.com/docs/setting-up-a-jwt-app) at Box's developer website.
+
+## Android
+If you are developing application for Android visit our [Android guide](doc/android.md).
 
 ## Quick Test
 

doc/android.md

@@ -0,0 +1,97 @@
+# Android
+
+The Java SDK should be compatible with modern Android applications written in both Java and Kotlin.
+
+To use the Java SDK in an android application add it to the project's gradle file in the `dependencies` block.
+
+For Groovy
+
+```groovy
+// build.gradle
+
+dependencies {
+    implementation "com.box:box-java-sdk:3.8.0"
+}
+```
+
+For Kotlin
+
+```kotlin
+// build.gradle.kts
+
+dependencies {
+    implementation("com.box:box-java-sdk:3.8.0")
+}
+```
+
+## Kotlin
+
+The Java SDK can also be used in Kotlin Android applications through interoperability thanks to the Kotlin design. 
+You can read more about Kotlin and Java interoperability [here](https://kotlinlang.org/docs/java-interop.html)
+
+The following example creates an API connection with a developer token:
+
+```kotlin
+val api = BoxAPIConnection("myToken")
+```
+
+The following example shows how to get current user 
+
+```kotlin
+val userID = "33333"
+val api = BoxAPIConnection("myToken")
+val user = BoxUser(api, userID)
+val userInfo = user.getInfo()
+```
+
+If you are using an IntelliJ-based IDE, you can copy our samples located in the [docs](/doc/) directory 
+and paste them into your file. The IDE should ask you to convert the pasted Java sample to Kotlin. Most samples still work after conversion using this approach.
+
+Note that the current Java SDK does not support Kotlin coroutines. By default, you cannot run network calls on the main thread 
+in an Android application. There are various ways to overcome this. For example, if you are in a viewModel context, you can run the SDK method as a 
+coroutine using viewModelScope.
+
+```kotlin
+viewModelScope.launch {
+    val result = withContext(Dispatchers.IO) {
+        /*
+            SDK code goes here
+        */
+    }
+    // here you can access the result and load it to the viewModel
+}
+```
+
+The following example shows how to get the current items in the root folder, sorted by name in ascending order with additional
+"created_by" and "name" fields returned from the API. The items are then loaded to the custom data class defined earlier.
+
+```kotlin
+// data class definition used in viewModel
+data class Item(
+    val isFolder: Boolean,
+    val name: String,
+    val createdBy: String
+)
+
+// viewModel init code
+viewModelScope.launch {
+    val result = withContext(Dispatchers.IO) {
+        val res = BoxFolder(BoxAPIConnection("myToken"), "0")
+        val iterator: Iterator<BoxItem.Info> =
+            res.getChildren("name", BoxFolder.SortDirection.ASC, "created_by", "name")
+                .iterator() 
+        val items = mutableListOf<Item>()
+
+        when (val itemInfo = iterator.next()) {
+            is BoxFile.Info -> items.add(Item(false, "File " + itemInfo.name, itemInfo.createdBy.name))
+            is BoxFolder.Info -> items.add(Item(true, "Folder " + itemInfo.name, itemInfo.createdBy.name)) 
+        }
+        items
+    }          
+}      
+```
+
+If you are familiar with Kotlin syntax, you might have noticed that we could have used the `.map` function (or a similar function) to map the API result to a list of items. Due to current limitations, using `.map` and similar operations on collections is not always possible and may 
+lead to unexpected results. The preferred way is to use an explicit iterator to iterate over the collections returned by the SDK.
+
+If you find any problem related to the Java SDK in Kotlin-based app feel free to open an issue.