Add "player" library module.

player/build.gradle

+apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
+
+android {
+    compileSdkVersion versions.compileSdk
+
+    defaultConfig {
+        minSdkVersion 21
+        targetSdkVersion versions.targetSdk
+        versionCode 1
+        versionName "1.0.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+
+    implementation libraries.kotlin
+
+    implementation libraries.appCompat
+
+    implementation libraries.exoPlayer
+
+    testImplementation libraries.junit
+}
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player/proguard-rules.pro

+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

player/src/main/AndroidManifest.xml

+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="chat.rocket.android.player">
+
+    <application>
+        <activity
+            android:name=".PlayerActivity"
+            android:configChanges="keyboard|keyboardHidden|orientation|screenSize|screenLayout|smallestScreenSize|uiMode"
+            android:theme="@style/PlayerTheme" />
+    </application>
+
+</manifest>
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player/src/main/java/chat/rocket/android/player/PlayerActivity.kt

+package chat.rocket.android.player
+
+import android.net.Uri
+import android.os.Bundle
+import android.support.v7.app.AppCompatActivity
+import android.view.View
+import com.google.android.exoplayer2.DefaultLoadControl
+import com.google.android.exoplayer2.DefaultRenderersFactory
+import com.google.android.exoplayer2.ExoPlayerFactory
+import com.google.android.exoplayer2.SimpleExoPlayer
+import com.google.android.exoplayer2.extractor.DefaultExtractorsFactory
+import com.google.android.exoplayer2.source.ExtractorMediaSource
+import com.google.android.exoplayer2.source.MediaSource
+import com.google.android.exoplayer2.trackselection.DefaultTrackSelector
+import com.google.android.exoplayer2.upstream.DefaultHttpDataSourceFactory
+import com.google.android.exoplayer2.util.Util
+import kotlinx.android.synthetic.main.activity_player.*
+
+class PlayerActivity : AppCompatActivity() {
+    private lateinit var player: SimpleExoPlayer
+    private var isPlayerInitialized = false
+    private var playWhenReady = true
+    private var currentWindow = 0
+    private var playbackPosition = 0L
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_player)
+    }
+
+    override fun onStart() {
+        super.onStart()
+        if (Util.SDK_INT > 23) {
+            initializePlayer()
+        }
+    }
+
+    override fun onResume() {
+        super.onResume()
+        hideSystemUi()
+        if (Util.SDK_INT <= 23 || !isPlayerInitialized) {
+            initializePlayer()
+        }
+    }
+
+    override fun onPause() {
+        super.onPause()
+        if (Util.SDK_INT <= 23) {
+            releasePlayer()
+        }
+    }
+
+    override fun onStop() {
+        super.onStop()
+        if (Util.SDK_INT > 23) {
+            releasePlayer()
+        }
+    }
+
+    private fun initializePlayer() {
+        if (!isPlayerInitialized) {
+            player = ExoPlayerFactory.newSimpleInstance(DefaultRenderersFactory(this), DefaultTrackSelector(), DefaultLoadControl())
+            player_view.player = player
+            player.playWhenReady = playWhenReady
+            player.seekTo(currentWindow, playbackPosition)
+            isPlayerInitialized = true
+        }
+        val uri = Uri.parse("http://download.blender.org/peach/bigbuckbunny_movies/BigBuckBunny_320x180.mp4")
+        val mediaSource = buildMediaSource(uri)
+        player.prepare(mediaSource, true, false)
+    }
+
+    private fun releasePlayer() {
+        if (isPlayerInitialized) {
+            playbackPosition = player.currentPosition
+            currentWindow = player.currentWindowIndex
+            playWhenReady = player.playWhenReady
+            player.release()
+            isPlayerInitialized = false
+        }
+    }
+
+    private fun buildMediaSource(uri: Uri): MediaSource = ExtractorMediaSource(uri, DefaultHttpDataSourceFactory("rocket-chat-android-player"), DefaultExtractorsFactory(), null, null)
+
+    private fun hideSystemUi() {
+        // Read the docs for detailed explanation: https://developer.android.com/training/basics/firstapp/starting-activity.html and https://developer.android.com/design/patterns/fullscreen.html
+         player_view.systemUiVisibility = View.SYSTEM_UI_FLAG_FULLSCREEN or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
+    }
+}
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player/src/main/res/layout/activity_player.xml

+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <com.google.android.exoplayer2.ui.SimpleExoPlayerView
+        android:id="@+id/player_view"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+</FrameLayout>
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player/src/main/res/values/strings.xml

+<resources>
+
+    <string name="app_name">Rocket Chat Android Player library</string>
+
+</resources>
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player/src/main/res/values/styles.xml

+<resources>
+
+    <style name="PlayerTheme" parent="Theme.AppCompat.NoActionBar">
+        <item name="android:windowBackground">@null</item>
+    </style>
+
+</resources>
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