implement "load more" placeholder

app/src/main/java/com/keylesspalace/tusky/adapter/PlaceholderViewHolder.java

@@ -0,0 +1,49 @@
+/* Copyright 2017 Andrew Dawson
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
+package com.keylesspalace.tusky.adapter;
+
+import android.support.v7.widget.RecyclerView;
+import android.view.View;
+import android.widget.Button;
+
+import com.keylesspalace.tusky.R;
+import com.keylesspalace.tusky.interfaces.StatusActionListener;
+
+public class PlaceholderViewHolder extends RecyclerView.ViewHolder {
+
+    private Button loadMoreButton;
+
+
+    PlaceholderViewHolder(View itemView) {
+        super(itemView);
+        loadMoreButton = itemView.findViewById(R.id.button_load_more);
+
+    }
+
+    public void setup(boolean enabled, final StatusActionListener listener){
+        loadMoreButton.setEnabled(enabled);
+        if(enabled) {
+            loadMoreButton.setOnClickListener(new View.OnClickListener() {
+                @Override
+                public void onClick(View v) {
+                    loadMoreButton.setEnabled(false);
+                    listener.onLoadMore(getAdapterPosition());
+                }
+            });
+        }
+    }
+
+}