Add getTextDrawable function.

app/src/main/java/chat/rocket/android/app/DrawableHelper.kt

 import android.content.Context
+import android.graphics.Typeface
 import android.graphics.drawable.Drawable
 import android.support.v4.content.ContextCompat
 import android.support.v4.graphics.drawable.DrawableCompat
 import android.widget.EditText
 import android.widget.TextView
 import chat.rocket.android.R
+import chat.rocket.android.helper.TextHelper
+import com.amulyakhare.textdrawable.TextDrawable
 
 object DrawableHelper {
-
+    private val AVATAR_BACKGROUND_HEXADECIMAL_COLORS = intArrayOf(
+            0xFFF44336.toInt(), 0xFFE91E63.toInt(), 0xFF9C27B0.toInt(), 0xFF673AB7.toInt(), 0xFF3F51B5.toInt(),
+            0xFF2196F3.toInt(), 0xFF03A9F4.toInt(), 0xFF00BCD4.toInt(), 0xFF009688.toInt(), 0xFF4CAF50.toInt(),
+            0xFF8BC34A.toInt(), 0xFFCDDC39.toInt(), 0xFFFFC107.toInt(), 0xFFFF9800.toInt(), 0xFFFF5722.toInt(),
+            0xFF795548.toInt(), 0xFF9E9E9E.toInt(), 0xFF607D8B.toInt())
     /**
      * Returns a Drawable from its ID.
      *
@@ -37,7 +44,7 @@ object DrawableHelper {
      * @see wrapDrawables
      * @see tintDrawable
      */
-    fun wrapDrawable(drawable: Drawable) = DrawableCompat.wrap(drawable)
+    fun wrapDrawable(drawable: Drawable): Drawable = DrawableCompat.wrap(drawable)
 
     /**
      * Tints an array of Drawable.
@@ -116,4 +123,29 @@ object DrawableHelper {
         }
         return userStatusDrawable
     }
+
+    /**
+     * Returns a drawable with the first character from a string.
+     *
+     * @param string The string to get its first character and to get the avatar background color.
+     * @return A drawable with the string first character.
+     */
+    fun getTextDrawable(string: String): Drawable {
+        return TextDrawable.builder()
+                .beginConfig()
+                .useFont(Typeface.SANS_SERIF)
+                .endConfig()
+                .buildRound(TextHelper.getFirstCharacter(string), getAvatarBackgroundColor(string))
+    }
+
+    /**
+     * Returns a background color to be rendered on the avatar.
+     *
+     * @param string Gets the background color based on the provided string.
+     * @return A hexadecimal color.
+     * @see (Rocket.Chat/server/startup/avatar.js)
+     */
+    private fun getAvatarBackgroundColor(string: String): Int {
+        return AVATAR_BACKGROUND_HEXADECIMAL_COLORS[string.length % AVATAR_BACKGROUND_HEXADECIMAL_COLORS.size]
+    }
 }
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