Add undo snackbar for deleting items

- Add methods to ModelWriter to prepareForUndoDelete, then
  enqueueDeleteRunnable, followed by commitDelete or abortDelete.
- Add Snackbar floating view
- Show Undo snackbar when dropping or flinging to delete target; if the
  undo action is clicked, we abort the delete, otherwise we commit it.

Bug: 24238108
Change-Id: I9997235e1f8525cbb8b1fa2338099609e7358426

1 files changed, 41 insertions, 0 deletions

diff --git a/res/layout/snackbar.xml b/res/layout/snackbar.xml
new file mode 100644
index 000000000..419fb8220
--- /dev/null
+++ b/res/layout/snackbar.xml
@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2018 The Android Open Source Project
+
+     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.
+-->
+
+<merge xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+    <TextView
+        android:id="@+id/label"
+        android:layout_height="@dimen/snackbar_content_height"
+        android:layout_width="0dp"
+        android:layout_weight="1"
+        android:gravity="center_vertical"
+        android:paddingLeft="8dp"
+        android:paddingRight="8dp"
+        android:textSize="14sp"
+        android:textColor="?android:attr/textColorPrimary"/>
+    <TextView
+        android:id="@+id/action"
+        android:layout_height="@dimen/snackbar_content_height"
+        android:layout_width="wrap_content"
+        android:layout_weight="0"
+        android:gravity="center"
+        android:padding="8dp"
+        android:background="?android:attr/selectableItemBackground"
+        android:textStyle="bold"
+        android:textColor="?android:attr/textColorPrimary"
+        android:textAllCaps="true"/>
+</merge>
\ No newline at end of file