Convert CustomViewActivity class to Kotlin.

app/src/main/java/com/vanniktech/emoji/sample/CustomViewActivity.kt

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2016 - Niklas Baudy, Ruben Gees, Mario Đanić and contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+package com.vanniktech.emoji.sample
+
+import android.content.Context
+import android.os.Bundle
+import android.util.AttributeSet
+import android.view.LayoutInflater
+import android.widget.LinearLayout
+import androidx.appcompat.app.AppCompatActivity
+import com.vanniktech.emoji.EmojiPopup
+import com.vanniktech.emoji.sample.databinding.ViewCustomBinding
+import com.vanniktech.emoji.traits.EmojiTrait
+
+class CustomViewActivity : AppCompatActivity() {
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+    val customView = CustomView(this, null)
+    setContentView(customView)
+    customView.setUpEmojiPopup()
+  }
+
+  internal class CustomView @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+  ) : LinearLayout(context, attrs) {
+    private val binding = ViewCustomBinding.inflate(LayoutInflater.from(context), this)
+
+    private var forceSingleEmoji: EmojiTrait? = null
+
+    init {
+      orientation = VERTICAL
+    }
+
+    fun setUpEmojiPopup() {
+      binding.onlyAllowSingleEmoji.setOnCheckedChangeListener { _, isChecked: Boolean ->
+        if (isChecked) {
+          forceSingleEmoji = binding.editText.installForceSingleEmoji()
+        } else if (forceSingleEmoji != null) {
+          forceSingleEmoji!!.uninstall()
+        }
+      }
+      val emojiPopup = EmojiPopup.Builder.fromRootView(this)
+        .setKeyboardAnimationStyle(R.style.emoji_fade_animation_style)
+        .setPageTransformer(PageTransformer())
+        .build(binding.editText)
+      binding.editText.disableKeyboardInput(emojiPopup)
+      binding.button.setOnClickListener { binding.editText.requestFocus() }
+    }
+  }
+}

app/src/main/res/layout/view_custom.xml

@@ -14,7 +14,7 @@
       android:text="Custom view which only allows emojis to be entered."
       />
   <Button
-      android:id="@+id/customViewButton"
+      android:id="@+id/button"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_margin="8dp"
@@ -28,7 +28,7 @@
       android:text="Only allow single emoji"
       />
   <com.vanniktech.emoji.EmojiEditText
-      android:id="@+id/customViewEditText"
+      android:id="@+id/editText"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:layout_margin="8dp"