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 /**
19  * The binding class keeps track of a binding between a ui component and an item of BindableData
20  * It allows each side to ensure that when it communicates with the other they are still bound
21  * together.
22  * NOTE: Ensure that the UI component uses the same binding instance for it's whole lifetime
23  *  (DO NOT CREATE A NEW BINDING EACH TIME A NEW PIECE OF DATA IS BOUND)...
24  *
25  * The ui component owns the binding instance.
26  * It can use it [isBound(data)] to see if the binding still binds to the right piece of data
27  *
28  * Upon binding the data is informed of a unique binding key generated in this class and can use
29  * that to ensure that it is still issuing callbacks to the right piece of ui.
30  */
31 public abstract class BindingBase<T extends BindableData> {
32     /**
33      * Creates a new exclusively owned binding for the owner object.
34      */
createBinding(final Object owner)35     public static <T extends BindableData> Binding<T> createBinding(final Object owner) {
36         return new Binding<T>(owner);
37     }
38 
39     /**
40      * Creates a new read-only binding referencing the source binding object.
41      * TODO: We may want to refcount the Binding references, so that when the binding owner
42      * calls unbind() when there's still outstanding references we can catch it.
43      */
createBindingReference( final BindingBase<T> srcBinding)44     public static <T extends BindableData> ImmutableBindingRef<T> createBindingReference(
45             final BindingBase<T> srcBinding) {
46         return new ImmutableBindingRef<T>(srcBinding);
47     }
48 
49     /**
50      * Creates a detachable binding for the owner object. Use this if your owner object is a UI
51      * component that may undergo a "detached from window" -> "re-attached to window" transition.
52      */
createDetachableBinding( final Object owner)53     public static <T extends BindableData> DetachableBinding<T> createDetachableBinding(
54             final Object owner) {
55         return new DetachableBinding<T>(owner);
56     }
57 
getData()58     public abstract T getData();
59 
60     /**
61      * Check if binding connects to the specified data instance
62      */
isBound()63     public abstract boolean isBound();
64 
65     /**
66      * Check if binding connects to the specified data instance
67      */
isBound(final T data)68     public abstract boolean isBound(final T data);
69 
70     /**
71      * Throw if binding connects to the specified data instance
72      */
ensureBound()73     public abstract void ensureBound();
74 
75     /**
76      * Throw if binding connects to the specified data instance
77      */
ensureBound(final T data)78     public abstract void ensureBound(final T data);
79 
80     /**
81      * Return the binding id for this binding (will be null if not bound)
82      */
getBindingId()83     public abstract String getBindingId();
84 }
85