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 android.databinding;
17
18/**
19 * Listener set on {@link ViewDataBinding#addOnRebindCallback(OnRebindCallback)} that
20 * is called when bound values must be reevaluated in {@link
21 * ViewDataBinding#executePendingBindings()}.
22 */
23public abstract class OnRebindCallback<T extends ViewDataBinding> {
24
25    /**
26     * Called when values in a ViewDataBinding should be reevaluated. This does not
27     * mean that values will actually change, but only that something in the data
28     * model that affects the bindings has been perturbed.
29     * <p>
30     * Return true to allow the reevaluation to happen or false if the reevaluation
31     * should be stopped. If false is returned, it is the responsibility of the
32     * OnRebindListener implementer to explicitly call {@link
33     * ViewDataBinding#executePendingBindings()}.
34     * <p>
35     * The default implementation only returns <code>true</code>.
36     *
37     * @param binding The ViewDataBinding that is reevaluating its bound values.
38     * @return true to indicate that the reevaluation should continue or false to
39     * halt evaluation.
40     */
41    public boolean onPreBind(T binding) {
42        return true;
43    }
44
45    /**
46     * Called after all callbacks have completed {@link #onPreBind(ViewDataBinding)} when
47     * one or more of the calls has returned <code>false</code>.
48     * <p>
49     * The default implementation does nothing.
50     *
51     * @param binding The ViewDataBinding that is reevaluating its bound values.
52     */
53    public void onCanceled(T binding) {
54    }
55
56    /**
57     * Called after values have been reevaluated in {@link
58     * ViewDataBinding#executePendingBindings()}. This is only called if all listeners have
59     * returned true from {@link #onPreBind(ViewDataBinding)}.
60     * <p>
61     * The default implementation does nothing.
62     *
63     * @param binding The ViewDataBinding that is reevaluating its bound values.
64     */
65    public void onBound(T binding) {
66    }
67}
68