/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License,
Version 2
.0 (the "License");
* you may not use this file except in compliance with the License
.
* You may obtain a copy of the License at
*
* http://www
.apache
.org/licenses/LICENSE-2
.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied
.
* See the License for the specific language governing permissions and
* limitations under the License
.
*/
package androidx
.databinding;
import java
.lang
.annotation
.ElementType;
import java
.lang
.annotation
.Target;
/**
* BindingAdapter is applied to methods that are used to manipulate how values with expressions
* are set to views
. The simplest example is to have a public static method that takes the view
* and the value to set:
* <p><pre>
*<code>@BindingAdapter("android:bufferType")
* public static void setBufferType(TextView view, TextView
.BufferType bufferType) {
* view
.setText(view
.getText(), bufferType);
* }</code></pre>
* In the above example, when android:bufferType is used on a TextView, the method
* setBufferType is called
.
* <p>
* It is also possible to take previously set values, if the old values are listed first:
* <p><pre>
*<code>@BindingAdapter("android:onLayoutChange")
* public static void setOnLayoutChangeListener(View view, View
.OnLayoutChangeListener oldValue,
* View
.OnLayoutChangeListener newValue) {
* if (
Build.VERSION.SDK_
INT >
= Build.VERSION_
CODES.HONEYCOMB) {
* if (oldValue !
= null) {
* view
.removeOnLayoutChangeListener(oldValue);
* }
* if (newValue !
= null) {
* view
.addOnLayoutChangeListener(newValue);
* }
* }
* }</code></pre>
* When a binding adapter may also take multiple attributes, it will only be called when all
* attributes associated with the binding adapter have binding expressions associated with them
.
* This is useful when there are unusual
interactions between attributes
. For example:
* <p><pre>
*<code>@BindingAdapter({"android:onClick", "android:clickable"})
* public static void setOnClick(View view, View
.OnClickListener clickListener,
* boolean clickable) {
* view
.setOnClickListener(clickListener);
* view
.setClickable(clickable);
* }</code></pre>
* The order of the parameters must match the order of the attributes in values in the
* BindingAdapter
.
* <p>
* A binding adapter may optionally take a class extending DataBindingComponent as the first
* parameter as well
. If it does, it will be passed the value passed in during binding, either
* directly in the inflate method or indirectly, using the value from
* {@link DataBindingUtil#getDefaultComponent()}
.
* <p>
* If a binding adapter is an instance method, the generated DataBindingComponent will have
* a getter to retrieve an instance of the BindingAdapter's class to use to call the method
.
*/
@Target(ElementType
.METHOD)
public @
interface BindingAdapter {
/**
* @return The attributes associated with this binding adapter
.
*/
String[] value();
/**
* Whether every attribute must be assigned a binding expression or if some
* can be absent
. When this is false, the BindingAdapter will be called
* when at least one associated attribute has a binding expression
. The attributes
* for which there was no binding expression (even a normal XML value) will
* cause the associated parameter receive the Java default value
. Care must be
* taken to ensure that a default value is not confused with a valid XML value
.
*
* @return whether or not every attribute must be assigned a binding expression
. The default
* value is true
.
*/
boolean requireAll() default true;
}
翻译并注释
本文介绍了Android系统中Build.VERSION和Build.VERSION_CODES的作用，详细解释了如何通过它们获取当前设备的Android版本信息，并展示了如何利用这些信息来判断并兼容新旧API。
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