1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package com.android.messaging.datamodel.binding;
17 
18 import com.android.messaging.util.Assert;
19 
20 /**
21  * An extension on {@link Binding} that allows for temporary data detachment from the UI component.
22  * This is used when, instead of destruction or data rebinding, the owning UI undergoes a
23  * "detached from window" -> "re-attached to window" transition, in which case we want to
24  * temporarily unbind the data and remember it so that it can be rebound when the UI is re-attached
25  * to window later.
26  */
27 public class DetachableBinding<T extends BindableData> extends Binding<T> {
28     private T mDetachedData;
29 
DetachableBinding(Object owner)30     DetachableBinding(Object owner) {
31         super(owner);
32     }
33 
34     @Override
bind(T data)35     public void bind(T data) {
36         super.bind(data);
37         // Rebinding before re-attaching. Pre-emptively throw away the detached data because
38         // it's now stale.
39         mDetachedData = null;
40     }
41 
detach()42     public void detach() {
43         Assert.isNull(mDetachedData);
44         Assert.isTrue(isBound());
45         mDetachedData = getData();
46         unbind();
47     }
48 
reAttachIfPossible()49     public void reAttachIfPossible() {
50         if (mDetachedData != null) {
51             Assert.isFalse(isBound());
52             bind(mDetachedData);
53             mDetachedData = null;
54         }
55     }
56 }
57