Convert java-esque code to Kotlin

Signed-off-by: Dominic Fischer <dominicfischer7@gmail.com>

vector/src/main/java/im/vector/riotx/EmojiCompatFontProvider.kt

@@ -50,7 +50,7 @@ class EmojiCompatFontProvider @Inject constructor(): FontsContractCompat.FontReq
     }
 
     fun addListener(listener: FontProviderListener) {
-        if (!listeners.contains(listener)) {
+        if (listener !in listeners) {
             listeners.add(listener)
         }
     }

vector/src/main/java/im/vector/riotx/core/dialogs/DialogAdapter.kt

@@ -26,14 +26,16 @@ import im.vector.riotx.R
 internal abstract class DialogAdapter(context: Context) : ArrayAdapter<DialogListItem>(context, R.layout.item_dialog) {
 
     override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View {
-        var view = convertView
-        if (view == null) {
+        val view: View
+        if (convertView == null) {
             view = LayoutInflater.from(context).inflate(R.layout.item_dialog, parent, false)
             view.tag = DialogListItemHolder(view)
+        } else {
+            view = convertView
         }
-        (view!!.tag as DialogListItemHolder).let {
-            it.icon.setImageResource(getItem(position).iconRes)
-            it.text.setText(getItem(position).titleRes)
+        with(view.tag as DialogListItemHolder) {
+            icon.setImageResource(getItem(position).iconRes)
+            text.setText(getItem(position).titleRes)
         }
         return view
     }

vector/src/main/java/im/vector/riotx/features/home/UserColor.kt

@@ -18,6 +18,7 @@ package im.vector.riotx.features.home
 
 import androidx.annotation.ColorRes
 import im.vector.riotx.R
+import kotlin.math.abs
 
 
 @ColorRes
@@ -36,7 +37,7 @@ fun getColorFromUserId(userId: String?): Int {
         i++
     }
 
-    return when (Math.abs(hash) % 8 + 1) {
+    return when (abs(hash) % 8 + 1) {
         1    -> R.color.riotx_username_1
         2    -> R.color.riotx_username_2
         3    -> R.color.riotx_username_3