Initial checkin of AOSP Messaging app.

b/23110861

Change-Id: I9aa980d7569247d6b2ca78f5dcb4502e1eaadb8a

src/com/android/messaging/datamodel/binding/DetachableBinding.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2015 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.
+ */
+package com.android.messaging.datamodel.binding;
+
+import com.android.messaging.util.Assert;
+
+/**
+ * An extension on {@link Binding} that allows for temporary data detachment from the UI component.
+ * This is used when, instead of destruction or data rebinding, the owning UI undergoes a
+ * "detached from window" -> "re-attached to window" transition, in which case we want to
+ * temporarily unbind the data and remember it so that it can be rebound when the UI is re-attached
+ * to window later.
+ */
+public class DetachableBinding<T extends BindableData> extends Binding<T> {
+    private T mDetachedData;
+
+    DetachableBinding(Object owner) {
+        super(owner);
+    }
+
+    @Override
+    public void bind(T data) {
+        super.bind(data);
+        // Rebinding before re-attaching. Pre-emptively throw away the detached data because
+        // it's now stale.
+        mDetachedData = null;
+    }
+
+    public void detach() {
+        Assert.isNull(mDetachedData);
+        Assert.isTrue(isBound());
+        mDetachedData = getData();
+        unbind();
+    }
+
+    public void reAttachIfPossible() {
+        if (mDetachedData != null) {
+            Assert.isFalse(isBound());
+            bind(mDetachedData);
+            mDetachedData = null;
+        }
+    }
+}