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 android.databinding;
17 
18 import java.lang.annotation.ElementType;
19 import java.lang.annotation.Target;
20 
21 /**
22  * BindingAdapter is applied to methods that are used to manipulate how values with expressions
23  * are set to views. The simplest example is to have a public static method that takes the view
24  * and the value to set:
25  * <p><pre>
26  *<code>@BindingAdapter("android:bufferType")
27  * public static void setBufferType(TextView view, TextView.BufferType bufferType) {
28  *     view.setText(view.getText(), bufferType);
29  * }</code></pre>
30  * In the above example, when android:bufferType is used on a TextView, the method
31  * setBufferType is called.
32  * <p>
33  * It is also possible to take previously set values, if the old values are listed first:
34  * <p><pre>
35  *<code>@BindingAdapter("android:onLayoutChange")
36  * public static void setOnLayoutChangeListener(View view, View.OnLayoutChangeListener oldValue,
37  *                                              View.OnLayoutChangeListener newValue) {
38  *     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
39  *         if (oldValue != null) {
40  *             view.removeOnLayoutChangeListener(oldValue);
41  *         }
42  *         if (newValue != null) {
43  *             view.addOnLayoutChangeListener(newValue);
44  *         }
45  *     }
46  * }</code></pre>
47  * When a binding adapter may also take multiple attributes, it will only be called when all
48  * attributes associated with the binding adapter have binding expressions associated with them.
49  * This is useful when there are unusual interactions between attributes. For example:
50  * <p><pre>
51  *<code>@BindingAdapter({"android:onClick", "android:clickable"})
52  * public static void setOnClick(View view, View.OnClickListener clickListener,
53  *                               boolean clickable) {
54  *     view.setOnClickListener(clickListener);
55  *     view.setClickable(clickable);
56  * }</code></pre>
57  * The order of the parameters must match the order of the attributes in values in the
58  * BindingAdapter.
59  * <p>
60  * A binding adapter may optionally take a class extending DataBindingComponent as the first
61  * parameter as well. If it does, it will be passed the value passed in during binding, either
62  * directly in the inflate method or indirectly, using the value from
63  * {@link DataBindingUtil#getDefaultComponent()}.
64  * <p>
65  * If a binding adapter is an instance method, the generated DataBindingComponent will have
66  * a getter to retrieve an instance of the BindingAdapter's class to use to call the method.
67  */
68 @Target(ElementType.METHOD)
69 public @interface BindingAdapter {
70 
71     /**
72      * @return The attributes associated with this binding adapter.
73      */
value()74     String[] value();
75 }
76