InverseBindingListener.java revision f2b497e3dc3946fec708fb8e86a29e234bf0506c 
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 * A listener implemented by all two-way bindings to be notified when a triggering change happens.
20 * For example, when there is a two-way binding for android:text, an implementation of
21 * <code>InverseBindingListener</code> will be generated in the layout's binding class.
22 * <pre>
23 * private static class InverseListenerTextView implements InverseBindingListener {
24 *     &commat;Override
25 *     public void onChange() {
26 *         mObj.setTextValue(mTextView.getText());
27 *     }
28 * }
29 * </pre>
30 * <p>
31 * A {@link BindingAdapter} should be used to assign the event listener.
32 * For example, <code>android:onTextChanged</code> will need to trigger the event listener
33 * for the <code>android:text</code> attribute.
34 * <pre>
35 * &commat;InverseBindingAdapter(attribute = "android:text", event = "android:textAttrChanged")
36 * public static void captureTextValue(TextView view, ObservableField&lt;CharSequence> value) {
37 *     CharSequence newValue = view.getText();
38 *     CharSequence oldValue = value.get();
39 *     if (oldValue == null) {
40 *         value.set(newValue);
41 *     } else if (!contentEquals(newValue, oldValue)) {
42 *         value.set(newValue);
43 *     }
44 * }
45 * &commat;BindingAdapter(value = {"android:beforeTextChanged", "android:onTextChanged",
46 *                          "android:afterTextChanged", "android:textAttrChanged"},
47 *                          requireAll = false)
48 * public static void setTextWatcher(TextView view, final BeforeTextChanged before,
49 *                                   final OnTextChanged on, final AfterTextChanged after,
50 *                                   final InverseBindingListener textAttrChanged) {
51 *     TextWatcher newValue = new TextWatcher() {
52 *         ...
53 *         &commat;Override
54 *         public void onTextChanged(CharSequence s, int start, int before, int count) {
55 *             if (on != null) {
56 *                 on.onTextChanged(s, start, before, count);
57 *             }
58 *             if (textAttrChanged != null) {
59 *                 textAttrChanged.onChange();
60 *             }
61 *         }
62 *     }
63 *     TextWatcher oldValue = ListenerUtil.trackListener(view, newValue, R.id.textWatcher);
64 *     if (oldValue != null) {
65 *         view.removeTextChangedListener(oldValue);
66 *     }
67 *     view.addTextChangedListener(newValue);
68 * }
69 * </pre>
70 */
71public interface InverseBindingListener {
72    /**
73     * Notifies the data binding system that the attribute value has changed.
74     */
75    void onChange();
76}
77