#51 convert RecyclerViewEmptySupport

Signed-off-by: YOUNG HO CHA <[email protected]>

app/src/main/java/com/example/avjindersinghsekhon/minimaltodo/RecyclerViewEmptySupport.kt

@@ -0,0 +1,54 @@
+package com.example.avjindersinghsekhon.minimaltodo
+
+import android.content.Context
+import android.support.v7.widget.RecyclerView
+import android.util.AttributeSet
+import android.view.View
+
+class RecyclerViewEmptySupport @JvmOverloads constructor(
+        context: Context, attrs: AttributeSet? = null, defStyle: Int = 0):
+        RecyclerView(context, attrs, defStyle) {
+    private var emptyView: View? = null
+
+    private val observer = object : RecyclerView.AdapterDataObserver() {
+        override fun onChanged() {
+            showEmptyView()
+        }
+
+        override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
+            super.onItemRangeInserted(positionStart, itemCount)
+            onChanged()
+        }
+
+        override fun onItemRangeRemoved(positionStart: Int, itemCount: Int) {
+            super.onItemRangeRemoved(positionStart, itemCount)
+            onChanged()
+        }
+    }
+
+    fun showEmptyView() {
+        val adapter = adapter
+        if (adapter != null && emptyView != null) {
+            if (adapter.itemCount == 0) {
+                emptyView!!.visibility = View.VISIBLE
+                visibility = View.GONE
+            } else {
+                emptyView!!.visibility = View.GONE
+                visibility = View.VISIBLE
+            }
+        }
+    }
+
+    override fun setAdapter(adapter: RecyclerView.Adapter<*>?) {
+        super.setAdapter(adapter)
+        adapter?.run {
+            registerAdapterDataObserver(observer)
+            observer.onChanged()
+        }
+    }
+
+    fun setEmptyView(v: View?) {
+        emptyView = v
+        showEmptyView()
+    }
+}