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 */
16package com.android.messaging.datamodel.binding;
17
18import 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 */
27public class DetachableBinding<T extends BindableData> extends Binding<T> {
28    private T mDetachedData;
29
30    DetachableBinding(Object owner) {
31        super(owner);
32    }
33
34    @Override
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
42    public void detach() {
43        Assert.isNull(mDetachedData);
44        Assert.isTrue(isBound());
45        mDetachedData = getData();
46        unbind();
47    }
48
49    public void reAttachIfPossible() {
50        if (mDetachedData != null) {
51            Assert.isFalse(isBound());
52            bind(mDetachedData);
53            mDetachedData = null;
54        }
55    }
56}
57