Android 无障碍辅助功能AccessibilityService（2）

让应用具有辅助功能 Making Applications Accessible

original: Applications built for Android are accessible to users with visual, physical or age-related disabilities when they activate accessibility features and services on a device. By default, these services make your application more accessible. However, there are further steps you should take to optimize the accessibility of your application and ensure a pleasant experience for all your users.
version: 许多Android用户有不同的能力（限制），这要求他们以不同的方式使用他们的Android设备。这些限制包括视力，肢体或与年龄有关，这些限制阻碍了他们看到或充分使用触摸屏，而用户的听力丧失，让他们可能无法感知声音信息和警报。然而,你应该采取进一步措施来优化应用程序的可访问性,确保所有用户的体验。
original: Making sure your application is accessible to all users is relatively easy, particularly when you use framework-provided user interface components. If you only use these standard components for your application, there are just a few steps required to ensure your application is accessible:
version: 确保你的应用程序可以贴近所有的用户，特别是当你使用Android框架提供的组件创建用户界面时，只需要几个步骤。如果在你的应用程序中只使用了标准组件，这些操作步骤是：
original: 1. Label your ImageButton, ImageView, EditText, CheckBox and other user interface controls using the android:contentDescription attribute.
version: 1. 为你应用中的用户界面控件，通过使用android:contentDescription属性，添加描述性文本， 尤其是ImageButton，ImageView和CheckBox控件。
original: 2. Make all of your user interface elements accessible with a directional controller, such as a trackball or D-pad.
version: 2. 确保所有用户界面元素，可以接受输入( 触摸或打字)，可以使用方向控制器如：一个轨迹球，方向键(物理或虚拟)或导航手势进行控制。
original: 3. Test your application by turning on accessibility services like TalkBack and Explore by Touch, and try using your application using only directional controls.
version: 3. 确保音频提示总是伴随着另一个视觉提示或通知,协助听力障碍的用户。
original: Developers who create custom controls that extend from the View class have some additional responsibilities for making sure their components are accessible for users. This document also discusses how to make custom view controls compatible with accessibility services.
version: 如果你构建自定义控件,扩展视图类,您必须完成一些额外的工作来确保你的组件是有辅助功能的。本文档讨论如何使自定义视图控制兼容的辅助功能服务。

用户界面的标签元素 Labeling User Interfaces Elements

original: Many user interface controls rely on visual cues to inform users of their meaning. For example, a note-taking application might use an ImageButton with a picture of a plus sign to indicate that the user can add a new note. Or, an EditText component may have a label near it that indicates its purpose. When a user with impaired vision accesses your application, these visual cues are often useless.
version: 许多用户界面控件依赖视觉线索来表示他们的意义和用法。例如,一个记笔记的应用程序可能会使用一个带加号图片的ImageButton表示用户可以添加一条新的笔记。在一个EditText组件旁边可能会有一个标签来说明需要输入的内容。视力较弱的用户看不到我们给出这些提示，这使得这些提示毫无用处。
original: To provide textual information about interface controls (as an alternative to the visual cues), use the android:contentDescription attribute. The text you provide in this attribute is not visible on the screen, but if a user has enabled accessibility services that provide audible prompts, then the description in this attribute is read aloud to the user.
version: 你可以使用在XML布局中的android:contentDescription 属性使这些控件更容易理解。 添加了这个属性的文本并不出现在屏幕上,但如果用户打开了提供声音提示的辅助功能服务,那么当用户进行访问控制时,文本会被讲出来。
original: Set the android:contentDescription attribute for every ImageButton, ImageView, EditText, CheckBox in your application’s user interface, and on any other input controls that might require additional information for users who are not able to see it.
version: 出于这个原因,将android:contentDescription属性应用在你应用程序用户界面的每个ImageButton, ImageView, EditText, CheckBox上，并且在其他输入控件中添加该属性,对于无法看到输入控件的用户，这些额外的信息是很有必要的。
original: For example, the following ImageButton sets the content description for the plus button to the add_note string resource, which could be defined as “Add note” for an English language interface:
version: 例如,下面的带加号的ImageButton设置了content description的string资源add_note,在英语界面中可能被定义为“Add note”

<ImageButton    android:id=”@+id/add_note_button”    android:src=”@drawable/add_note”    android:contentDescription=”@string/add_note”/> 

original: By including the description, speech-based accessibility services can announce “Add note” when a user moves focus to this button or hovers over it.
version: 由于添加了这个属性，当用户移动焦点到这个按钮或将鼠标悬停在它上面时，提供口头反馈的辅助功能服务就会发出“Add note”。
original: Note: For EditText fields, provide an android:hint attribute to help users understand what content is expected.
version: 注:对于EditText控件，提供了一个android:hint属性代替了contentDescription属性,这个属性可以在内容为空时，提示用户应该输入的内容。当输入完成后,TalkBack 读出输入内容给用户,不再是提示的文本内容。

启用焦点导航 Enabling Focus Navigation

original: Focus navigation allows users with disabilities to step through user interface controls using a directional controller. Directional controllers can be physical, such as a clickable trackball, directional pad (D-pad) or arrow keys, tab key navigation with an attached keyboard or a software application, such as the Eyes-Free Keyboard, that provides an on-screen directional control.
version: 焦点导航允许残疾用户使用方向控制器完成对用户界面控件的操作。方向控制器可以是物理的,比如一个轨迹球,方向键(摇杆)或箭头键,或是虚拟的,如Eyes-Free Keyboard，在Android 4.1和更高版本中的手势导航模式。方向控制器是许多Android用户的一个主要导航手段。
original: A directional controller is a primary means of navigation for many users. Verify that all user interface (UI) controls in your application are accessible without using the touchscreen and that clicking with the center button (or OK button) of a directional controller has the same effect as touching the controls on the touchscreen. For information on testing directional controls, see Testing focus navigation.
version: 确保用户在你的应用程序只使用一个方向控制器，不使用触摸屏就可以验证你应用程序可以到达的所有用户界面(UI)的输入控件。你也可以点击方向控制器的中心按钮(或OK按钮)，点击的效果和触摸已经获取焦点的按钮的效果相同。关于测试方向控制的内容,参考测试焦点导航一节。

启用视图焦点 Enabling view focus

original: A user interface element is accessible using directional controls when its android:focusable attribute is set to true. This setting allows users to focus on the element using the directional controls and then interact with it. The user interface controls provided by the Android framework are focusable by default and visually indicate focus by changing the control’s appearance.
version: 一个用户界面元素，其android:focusable属性设置为true时，是可以使用方向控制的。此设置在元素获取焦点后，允许用户使用方向控制与之交互。Android框架提供的用户界面控制，在默认情况下都是获取焦点和可见的，通过改变控件的外观来表明当前焦点的存在与否。
original: Android provides several APIs that let you control whether a user interface control is focusable and even request that a control be given focus:
version: Android提供了几个api允许您控制用户界面控制是否可以获取焦点，是否可以获取一个焦点：
setFocusable()//获取焦点
isFocusable()//是否失去焦点
requestFocus()//优先获取焦点

original: When working with a view that is not focusable by default, you can make it focusable from the XML layout file by setting the [[ http://android-doc.com/reference/android/view/View.html#attr_android:focusable | android:focusable ]] attribute to true or by using the setFocusable() method.
version: 如果一个view是缺省情况下是没有焦点的,可以在你的布局文件中通过设置android:focusable属性为true或通过调用其setFocusable()方法来获取焦点。

控制焦点的顺序 Controlling focus order

original: When users navigate in any direction using directional controls, focus is passed from one user interface element (View) to another, as determined by the focus ordering. The ordering of the focus movement is based on an algorithm that finds the nearest neighbor in a given direction. In rare cases, the default algorithm may not match the order that you intended for your UI. In these situations, you can provide explicit overrides to the ordering using the following XML attributes in the layout file:
version: 当用户在任何方向使用方向控制导航，焦点会确定的顺序从一个用户界面元素(视图)到另一个。这个顺序是根据一个算法,这个算法在一个给定的方向上寻找最近的邻居。在极端的情况下,该算法可能不匹配这个确定的顺序,可能不符合用户的逻辑。在这些情况下,您可以在你的布局文件使用下面的XML属性显式的指定焦点的顺序:
android:nextFocusDown
original: Defines the next view to receive focus when the user navigates down.
version: 定义当用户按导航下键时接收焦点的view
android:nextFocusLeft
original: Defines the next view to receive focus when the user navigates left.
version: 定义当用户按导航左键时接收焦点的view
android:nextFocusRight
original: Defines the next view to receive focus when the user navigates right.
version: 定义当用户按导航右键时接收焦点的view
android:nextFocusUp
original: Defines the next view to receive focus when the user navigates up.
version: 定义当用户按导航上键时接收焦点的view
original: The following example XML layout shows two focusable user interface elements where the android:nextFocusDown and android:nextFocusUp attributes have been explicitly set. The TextView is located to the right of the EditText. However, since these properties have been set, the TextView element can now be reached by pressing the down arrow when focus is on the EditText element:
version: 下面的示例XML布局展示了两个focusable用户界面元素,android:nextFocusDown和android:nextFocusUp属性被显式地设置。TextView在EditText的右边。 然而,由于这些属性的设置，当焦点在EditText元素上，通过按向下箭头键焦点切换到TextView元素上。

<LinearLayout android:orientation="horizontal"        ... >    <EditText android:id="@+id/edit"        android:nextFocusDown=”@+id/text”        ... />    <TextView android:id="@+id/text"        android:focusable=”true”        android:text="Hello, I am a focusable TextView"        android:nextFocusUp=”@id/edit”        ... /></LinearLayout>

original: When modifying focus order, be sure that the navigation works as expected in all directions from each user interface control and when navigating in reverse (to get back to where you came from).
version: 当修改焦点的顺序,确保导航在每个用户界面控件中各个方向焦点是按照预期的顺序的切换，在反向（焦点切换到当前控件的上一控件）是按照预期的顺序切换。
original: Note: You can modify the focus order of user interface components at runtime, using methods such as setNextFocusDownId() and setNextFocusRightId().
version: 注:您可以在用户界面组件运行时修改焦点的顺序,使用方法如setNextFocusDownId()和setNextFocusRightId()。

创建辅助功能的自定义视图 Building Accessible Custom Views

original: If your application requires a custom view component, you must do some additional work to ensure that your custom view is accessible. These are the main tasks for ensuring the accessibility of your view:
version: 如果您的应用程序需要一个自定义的视图组件,你必须做一些额外的工作来确保您的自定义视图是支持辅助功能。这些是主要的任务,确保你的视图的辅助功能:

• original: Handle directional controller clicks
• version: 处理方向控制器点击
• original: Implement Accessibility API methods
• version: 实现accessibility API 的方法
• original: Send AccessibilityEvent objects specific to your custom view
• version: 发送你自定义视图特定的AccessibilityEvent对象
• original: Populate AccessibilityEvent and AccessibilityNodeInfo for your view
• version: 为你自定义视图填充AccessibilityEvent和AccessibilityNodeInfo对象

处理方向控制器点击 Handling directional controller clicks

original: On most devices, clicking a view using a directional controller sends a KeyEvent with KEYCODE_DPAD_CENTER to the view currently in focus. All standard Android views already handle KEYCODE_DPAD_CENTER appropriately. When building a custom View control, make sure this event has the same effect as touching the view on the touchscreen.
version: 在多数的设备,使用方向控制器点击视图发送一个带KEYCODE_DPAD_CENTER的KeyEvent到当前焦点的视图。所有标准Android的view已经对KEYCODE_DPAD_CENTER适当处理。 当构建一个自定义的视图控制,确保这一事件,与在触摸屏触摸视图具有相同的效果。
original: Your custom control should also treat the KEYCODE_ENTER event the same as KEYCODE_DPAD_CENTER. This approach makes interaction from a full keyboard much easier for users.
version: 自定义控制也应该使KEYCODE_ENTER对应的输入事件与KEYCODE_DPAD_CENTER一样。这种方法使用户更容易通过全键盘进行交互。

实现accessibility API 的方法 Implementing accessibility API methods

original: Accessibility events are messages about users interaction with visual interface components in your application. These messages are handled by Accessibility Services, which use the information in these events to produce supplemental feedback and prompts when users have enabled accessibility services. As of Android 4.0 (API Level 14) and higher, the methods for generating accessibility events have been expanded to provide more detailed information beyond the AccessibilityEventSource interface introduced in Android 1.6 (API Level 4). The expanded accessibility methods are part of the View class as well as the View.AccessibilityDelegate class. The methods are as follows:
version: 在应用程序中，辅助功能事件是用户与可视界面组件交互的消息。这些消息是由辅助功能服务处理。辅助功能服务使用在这些事件中的信息产生附加的反馈和提示。Android 4.0(API级别14)和更高版本上，比Android 1.6(API级别4)中介绍的AccessibilityEventSource界面，辅助功能事件已经扩展，可以提供更详细的信息。扩展后的辅助功能方法属于View类的一部分，也是View.AccessibilityDelegate的一部分。方法如下:
sendAccessibilityEvent()
original: (API Level 4) This method is called when a user takes action on a view. The event is classified with a user action type such as TYPE_VIEW_CLICKED. You typically do not need to implement this method unless you are creating a custom view.
version: (API级别4)当用户在一个视图操作时调用此方法。事件是按照用户操作类型分类,如TYPE_VIEW_CLICKED。你通常不需要实现该方法,除非你是创建一个自定义视图。
sendAccessibilityEventUnchecked()
original: (API Level 4) This method is used when the calling code needs to directly control the check for accessibility being enabled on the device (AccessibilityManager.isEnabled()). If you do implement this method, you must assume that the calling method has already checked that accessibility is enabled and the result is true. You typically do not need to implement this method for a custom view.
version: (API级别4)当调用代码需要直接控制检查辅助功能设备的启用时，调用该方法。(AccessibilityManager.isEnabled())。如果你实现这个方法,不管实际的系统设置，执行调用时，必须假设辅助功能是启用的。一个自定义的视图，通常不需要实现该方法的。
dispatchPopulateAccessibilityEvent()
original: (API Level 4) The system calls this method when your custom view generates an accessibility event. As of API Level 14, the default implementation of this method calls onPopulateAccessibilityEvent() for this view and then the dispatchPopulateAccessibilityEvent() method for each child of this view. In order to support accessibility services on revisions of Android prior to 4.0 (API Level 14) you must override this method and populate getText() with descriptive text for your custom view.
version: (API级别4)当你的自定义视图生成一个辅助功能的事件时，系统调用这个方法。在API级别14,为当前视图，默认调用该方法的实现onPopulateAccessibilityEvent(),然后为当前视图的的子视图调用dispatchPopulateAccessibilityEvent()。在Android 4.0之前(API级别14)，为了支持辅助功能服务，在自定义视图中，必须重写此方法和用描述性文本填充getText(),这就是所说的辅助功能服务,如TalkBack。
onPopulateAccessibilityEvent()
original: (API Level 14) This method sets the text output of an AccessibilityEvent for your view. This method is also called if the view is a child of a view which generates an accessibility event.
version: (API级别14)这个方法在你的视图中设置AccessibilityEvent接口中的语音提示文本。如果当前视图是产生辅助功能事件视图的子视图，也要调用该方法。
original: Note: Modifying additional attributes beyond the text within this method potentially overwrites properties set by other methods. So, while you are able modify attributes of the accessibility event with this method, you should limit these changes to text content only and use the onInitializeAccessibilityEvent() method to modify other properties of the event.
version: 注:在当前方法的文本上修改附加属性，可能覆盖属性设置的其他方法。虽然您可以修改辅助功能事件方法中的属性，您应该限制这些对文本内容的修改,并使用onInitializeAccessibilityEvent()方法来修改其它事件的属性。
original: Note: If your implementation of this event calls for completely overiding the output text without allowing other parts of your layout to modify its content, then do not call the super implementation of this method in your code.
version: 注:如果这一事件的实现方法完全重写了输出文本，并且这些文本不允许布局中其它部分修改其内容，这时不必在代码中调用父类的方法的实现。
onInitializeAccessibilityEvent()
original: (API Level 14) The system calls this method to obtain additional information about the state of the view, beyond text content. If your custom view provides interactive control beyond a simple TextView or Button, you should override this method and set the additional information about your view into the event using this method, such as password field type, checkbox type or states that provide user interaction or feedback. If you do override this method, you must call its super implementation and then only modify properties that have not been set by the super class.
version: (API级别14)系统调用这个方法在当前文本中，获取视图的状态信息。如果自定义视图在TextView或Button上提供了交互式控制,你应该重写此方法，并需要在这个事件中设置你的视图的状态信息。这些状态信息如密码字段类型,复选框类型或,提供用户交互或反馈的状态信息。如果你做重写这个方法,您必须调用它父类的实现,然后只修改在超类中没有设置的属性。
onInitializeAccessibilityNodeInfo()
original: (API Level 14) This method provides accessibility services with information about the state of the view. The default View implementation sets a standard set of view properties, but if your custom view provides interactive control beyond a simple TextView or Button, you should override this method and set the additional information about your view into the AccessibilityNodeInfo object handled by this method.
version: (API级别14)这种方法提供了视图状态信息辅助功能服务。默认视图实现一组标准的视图属性，但如果您的自定义视图在TextView或Button提供了交互式控制服务,您应该重写此方法，并且通过该方法在AccessibilityNodeInfo对象中设置你试图的额外的信息。
onRequestSendAccessibilityEvent()
original: (API Level 14) The system calls this method when a child of your view has generated an AccessibilityEvent. This step allows the the parent view to amend the accessibility event with additional information. You should implement this method only if your custom view can have child views and if the parent view can provide context information to the accessibility event that would be useful to accessibility services.
version: (API级别14)当你视图中的子视图产生了一个AccessibilityEvent，系统调用这个方法。这个步骤允许父视图修改辅助功能的事件和其他信息。如果你的自定义视图有子视图,如果父视图可以对辅助功能服务有用的事件提供上下文信息，此时，必须实现该方法。
original: In order to support these accessibility methods for a custom view, you should take one of the following approaches:
version: 为了支持自定义的视图的这些辅助功能方法，应该采取以下方法:

• original: If your application targets Android 4.0 (API level 14) and higher, override and implement the accessibility methods listed above directly in your custom view class.
• version: 如果你的应用程序是Android 4.0(API级别14)以上，直接在自定义视图类中覆盖并实现上面列出的辅助功能方法。
• original: If your custom view is intended to be compatible with Android 1.6 (API Level 4) and above, add the Android Support Library, revision 5 or higher, to your project. Then, within your custom view class, call the ViewCompat.setAccessibilityDelegate() method to implement the accessibility methods above. For an example of this approach, see the Android Support Library (revision 5 or higher) sample AccessibilityDelegateSupportActivity in (/extras/android/support/v4/samples/Support4Demos/)
• original: 如果自定义视图为兼容安卓1.6(API 4级)及以上,对你的项目中加上Android Support Library，版本5或更高。然后,在您的自定义视图类,调用ViewCompat.setAccessibilityDelegate()方法来实现上面的辅助功能方法。 对于这种方法的一个示例,请参阅Android支持库(修订5或更高)示例。AccessibilityDelegateSupportActivity(/extras/android/support/v4/samples/Support4Demos/)

original: In either case, you should implement the following accessibility methods for your custom view class:
version: 在这两种情况下,你应该在自定义视图类中实现以下辅助功能方法:
dispatchPopulateAccessibilityEvent()
onPopulateAccessibilityEvent()
onInitializeAccessibilityEvent()
onInitializeAccessibilityNodeInfo()
original: For more information about implementing these methods, see Populating Accessibility Events.
version: 关于这些方法更多的实施信息,请参阅填充辅助功能事件一节。

发送辅助功能事件 Sending accessibility events

original: Depending on the specifics of your custom view, it may need to send AccessibilityEvent objects at a different times or for events not handled by the default implementation. The View class provides a default implementation for these event types:
version: 根据您的自定义视图的细节,它可能需要在不同时间或系统默认没有实现的事件发送AccessibilityEvent对象。视图类对这些事件类型提供了一个默认实现:
Starting with API Level 4://从API四级开始
TYPE_VIEW_CLICKED
TYPE_VIEW_LONG_CLICKED
TYPE_VIEW_FOCUSED
Starting with API Level 14://从API级别14开始
TYPE_VIEW_SCROLLED
TYPE_VIEW_HOVER_ENTER
TYPE_VIEW_HOVER_EXIT
original: Note: Hover events are associated with the Explore by Touch feature, which uses these events as triggers for providing audible prompts for user interface elements.
version: 注:悬停事件与浏览器的触摸属性有关，通常将这些悬停时间作为在用户界面元素提供声音提示的触发器。
original: In general, you should send an AccessibilityEvent whenever the content of your custom view changes. For example, if you are implementing a custom slider bar that allows a user to select a numeric value by pressing the left or right arrows, your custom view should emit an event of type TYPE_VIEW_TEXT_CHANGED whenever the slider value changes. The following sample code demonstrates the use of the sendAccessibilityEvent() method to report this event.
version: 一般来说,每当你的自定义视图的内容变化时，应该发送一个AccessibilityEvent。例如,如果您正在实现一个自定义滚动条,允许用户按左或右箭头选择一个数值,当滑块的值改变时，自定义视图应该发出一个事件类型TYPE_VIEW_TEXT_CHANGED。下面的示例代码演示了如何使用该sendAccessibilityEvent()方法来报告这个事件。

@Overridepublic boolean onKeyUp (int keyCode, KeyEvent event) {    if (keyCode == KeyEvent.KEYCODE_DPAD_LEFT) {        mCurrentValue--;        sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED);        return true;    }    ...}

填充辅助功能事件 Populating accessibility events

original: Each AccessibilityEvent has a set of required properties that describe the current state of the view. These properties include things such as the view’s class name, content description and checked state. The specific properties required for each event type are described in the AccessibilityEvent reference documentation. The View implementation provides default values for these properties. Many of these values, including the class name and event timestamp, are provided automatically. If you are creating a custom view component, you must provide some information about the content and characteristics of the view. This information may be as simple as a button label, but may also include additional state information that you want to add to the event.
version: 每个AccessibilityEvent有一组必需的描述当前状态的视图的属性。这些属性包括诸如视图的类名称、内容描述和检查状态。在AccessibilityEvent参考文档中描述了每个事件类型的特定属性要求。视图的实现提供了这些属性的默认值。这些值中包括包括类名和事件的时间戳。如果你正在创建一个自定义的视图组件,您必须提供一些关于内容和特征的信息。这个信息可能只要一个按钮的标签,但也可能包括你想添加到事件的额外状态信息。
original: The minimum requirement for providing information to accessibility services with a custom view is to implement dispatchPopulateAccessibilityEvent(). This method is called by the system to request information for an AccessibilityEvent and makes your custom view compatible with accessibility services on Android 1.6 (API Level 4) and higher. The following example code demonstrates a basic implementation of this method.
version: 提供无障碍服务与一个自定义视图的最低要求是实现dispatchPopulateAccessibilityEvent()。这个方法被系统调用，要求AccessibilityEvent在自定义视图兼容的辅助功能服务在Android 1.6(API级别4)以上。下面的示例代码演示了该方法的基本实现。

@Overridepublic void dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {    super.dispatchPopulateAccessibilityEvent(event);    // Call the super implementation to populate its text to the event, which    // calls onPopulateAccessibilityEvent() on API Level 14 and up.    // In case this is running on a API revision earlier that 14, check    // the text content of the event and add an appropriate text    // description for this custom view:    CharSequence text = getText();    if (!TextUtils.isEmpty(text)) {        event.getText().add(text);    }}

original: On Android 4.0 (API Level 14) and higher, the onPopulateAccessibilityEvent() and onInitializeAccessibilityEvent() methods are the recommended way to populate or modify the information in an AccessibilityEvent. Use the onPopulateAccessibilityEvent() method specifically for adding or modifying the text content of the event, which is turned into audible prompts by accessibility services such as TalkBack. Use the onInitializeAccessibilityEvent() method for populating additional information about the event, such as the selection state of the view.
version: Android 4.0(API级别14)以上,使用onPopulateAccessibilityEvent()和onInitializeAccessibilityEvent()方法来填充或修改在一个AccessibilityEvent的内容。 使用onPopulateAccessibilityEvent()方法专门为添加或修改事件的文本内容,这些文本内容最终会转换为诸如TalkBack的声音提示。使用onInitializeAccessibilityEvent()方法用于填充事件的其他信息,比如选择视图的状态。
original: In addition, you should also implement the onInitializeAccessibilityNodeInfo() method. AccessibilityNodeInfo objects populated by this method are used by accessibility services to investigate the view hierarchy that generated an accessibility event after receiving that event, to obtain a more detailed context information and provide appropriate feedback to users.
version: 此外,实现onInitializeAccessibilityNodeInfo()方法来填充 AccessibilityNodeInfo对象，通过该方法可查看的视图层次,在收到该事件时生成一个辅助功能的事件,为了获得一个更详细的上下文信息,并提供适当的反馈给用户。
original: The example code below shows how override these three methods by using ViewCompat.setAccessibilityDelegate(). Note that this sample code requires that the Android Support Library for API Level 4 (revision 5 or higher) is added to your project.
version: 下面的代码示例显示了如何通过使用ViewCompat.setAccessibilityDelegate()覆盖这三个方法。 注意,此示例代码要求在你的项目中添加Android Support Library API 4(版本5或更高)。

ViewCompat.setAccessibilityDelegate(new AccessibilityDelegateCompat() {    @Override    public void onPopulateAccessibilityEvent(View host, AccessibilityEvent event) {        super.onPopulateAccessibilityEvent(host, event);        // We call the super implementation to populate its text for the        // event. Then we add our text not present in a super class.        // Very often you only need to add the text for the custom view.        CharSequence text = getText();        if (!TextUtils.isEmpty(text)) {            event.getText().add(text);        }    }    @Override    public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) {        super.onInitializeAccessibilityEvent(host, event);        // We call the super implementation to let super classes        // set appropriate event properties. Then we add the new property        // (checked) which is not supported by a super class.        event.setChecked(isChecked());    }    @Override    public void onInitializeAccessibilityNodeInfo(View host,            AccessibilityNodeInfoCompat info) {        super.onInitializeAccessibilityNodeInfo(host, info);        // We call the super implementation to let super classes set        // appropriate info properties. Then we add our properties        // (checkable and checked) which are not supported by a super class.        info.setCheckable(true);        info.setChecked(isChecked());        // Quite often you only need to add the text for the custom view.        CharSequence text = getText();        if (!TextUtils.isEmpty(text)) {            info.setText(text);        }    }}

original: On applications targeting Android 4.0 (API Level 14) and higher, these methods can be implemented directly in your custom view class. For another example of this approach, see the Android Support Library (revision 5 or higher) sample AccessibilityDelegateSupportActivity in (/extras/android/support/v4/samples/Support4Demos/).
version: 在Android 4.0(API级别14)以上的应用程序中,您可以在您的自定义视图类中直接实现这些方法。对于这种方法的另一个示例,请参见 Android Support Library(版本5或更高)示例AccessibilityDelegateSupportActivity在(/extras/android/support/v4/samples/Support4Demos/).
original: Note: You may find information on implementing accessibility for custom views written prior to Android 4.0 that describes the use of the dispatchPopulateAccessibilityEvent() method for populating AccessibilityEvents. As of the Android 4.0 release, however, the recommended approach is to use the onPopulateAccessibilityEvent() and onInitializeAccessibilityEvent() methods.
version: 注:你可能会发现在自定义视图中实现辅助功能之前，Android 4.0描述了使用dispatchPopulateAccessibilityEvent()方法填充AccessibilityEvents。在Android 4.0版本,然而,推荐的方法是使用onPopulateAccessibilityEvent()和onInitializeAccessibilityEvent()方法。

提供一个自定义辅助功能的上下文 Providing a customized accessibility context

original: In Android 4.0 (API Level 14), the framework was enhanced to allow accessibility services to inspect the containing view hierarchy of a user interface component that generates an accessibility event. This enhancement allows accessibility services to provide a much richer set of contextual information with which to aid users.
version: 在Android 4.0(API级别14)的框架增强了辅助功能服务检查，包含用户界面组件的视图层次,生成一个可访问性的事件。框架允许辅助功能服务提供一个丰富的,上下文信息来帮助用户。
original: There are some cases where accessibility services cannot get adequate information from the view hierarchy. An example of this is a custom interface control that has two or more separately clickable areas, such as a calendar control. In this case, the services cannot get adequate information because the clickable subsections are not part of the view hierarchy.
version: 有些情况下,辅助功能服务不能从视图层得到足够的信息。比如一个自定义控件,两个或两个以上的点击区域,如日历控件。在这种情况下,服务不能得到足够的信息,因为可点击的部分不包含在视图层上。
original: In the example shown in Figure 1, the entire calendar is implemented as a single view, so if you do not do anything else, accessibility services do not receive enough information about the content of the view and the user’s selection within the view. For example, if a user clicks on the day containing 17, the accessibility framework only receives the description information for the whole calendar control. In this case, the TalkBack accessibility service would simply announce “Calendar” or, only slightly better, “April Calendar” and the user would be left to wonder what day was selected.
version: 在图中所示的例子中,整个日历被当作一个单独的视图，所以如果你不做其它事,辅助性服务得不到关于视图内容和用户在视图中选择的足够信息。例如,如果用户点击17号那天,辅助性框架只接收描述对整个日历控件的信息。在这种情况下,辅助反馈服务只会发出“Calendar”，好点的情况发出”April Calendar”的反馈，用户想知道哪天被选中。
original: To provide adequate context information for accessibility services in situations like this, the framework provides a way to specify a virtual view hierarchy. A virtual view hierarchy is a way for application developers to provide a complementary view hierarchy to accessibility services that more closely matches the actual information on screen. This approach allows accessibility services to provide more useful context information to users.
version: 为了对辅助性服务提供足够的上下文信息，,框架提供了一种指定一个虚拟视图层次的方法。虚拟视图层次结构为应用程序开发人员提供一个互补的视图层，更接近在屏幕上实际的信息。这种方法允许辅助性服务给用户提供更多有用的上下文信息。
original: Another situation where a virtual view hierarchy may be needed is a user interface containing a set of controls (views) that have closely related functions, where an action on one control affects the contents of one or more elements, such as a number picker with separate up and down buttons. In this case, accessibility services cannot get adequate information because action on one control changes content in another and the relationship of those controls may not be apparent to the service. To handle this situation, group the related controls with a containing view and provide a virtual view hierarchy from this container to clearly represent the information and behavior provided by the controls.
version: 一个虚拟视图层次可能使用的另一个情况是：一个用户界面包含一组控件(视图),功能相近,在一个控件上的动作影响一个或多个元素的内容,比如一个带单独的向上和向下按钮的数字选择器。在这种情况下,辅助性服务无法得到足够的上下文信息，因为在一个控件上的动作，要改变另一个控件的内容，这些控件的依赖关系在服务中是无法知道的。为了处理这种情况,用一个包含这些相关控件组的视图，并为这个视图提供一个虚拟视图层，这个虚拟的视图层能够提供这些组件的信息和行为。

处理自定义的触摸事件 Handling custom touch events

original: Custom view controls may require non-standard touch event behavior. For example, a custom control may use the onTouchEvent(MotionEvent) listener method to detect the ACTION_DOWN and ACTION_UP events and trigger a special click event. In order to maintain compatibility with accessibility services, the code that handles this custom click event must do the following:
version: 自定义视图控件可能需要非标准的触摸事件的行为。例如,一个自定义控件可以使用onTouchEvent(MotionEvent)来侦测ACTION_DOWN 和 ACTION_UP事件,触发特殊的单击事件。为了与辅助性服务保持兼容性,代码处理该自定义点击事件必须做到以下几点:
original: 1. Generate an appropriate AccessibilityEvent for the interpreted click action.
version: 1. 生成一个接近解释AccessibilityEvent的点击动作。
original: 2. Enable accessibility services to perform the custom click action for users who are not able to use a touch screen.
version: 2. 对不能使用触摸屏的用户提供自定义点击动作的辅助性服务。
original: To handle these requirements in an efficient way, your code should override the performClick() method, which must call the super implementation of this method and then execute whatever actions are required by the click event. When the custom click action is detected, that code should then call your performClick() method. The following code example demonstrates this pattern.
version: 为了用一个有效的方法来处理这些需求,代码应该重写performClick()方法,该方法必须调用超类方法的实现,然后执行任何需要通过点击事件完成的操作。当检测到自定义点击击动作,代码应该调用你的performClick()方法。下面的代码示例演示了这种模式。

class CustomTouchView extends View {    public CustomTouchView(Context context) {        super(context);    }    boolean mDownTouch = false;    @Override    public boolean onTouchEvent(MotionEvent event) {        super.onTouchEvent(event);        // Listening for the down and up touch events        switch (event.getAction()) {            case MotionEvent.ACTION_DOWN:                mDownTouch = true;                return true;            case MotionEvent.ACTION_UP:                if (mDownTouch) {                    mDownTouch = false;                    performClick(); // Call this method to handle the response, and                                    // thereby enable accessibility services to                                    // perform this action for a user who cannot                                    // click the touchscreen.                    return true;                }        }        return false; // Return false for other touch events    }    @Override    public boolean performClick() {        // Calls the super implementation, which generates an AccessibilityEvent        // and calls the onClick() listener on the view, if any        super.performClick();        // Handle the action for the custom click here        return true;    }   }

original: The pattern shown above makes sure that the custom click event is compatible with accessibility services by using the performClick() method to both generate an accessibility event and provide an entry point for accessibility services to act on behalf of a user to perform this custom click event.
version: 上面所示的模式通过调用performClick()方法确保了自定义点击事件是与辅助性服务兼容的，performClick()方法既生成一个辅助性事件,又提供一个访问辅助性服务的入口，来代表用户执行了自定义的点击事件。
original: Note: If your custom view has distinct clickable regions, such as a custom calendar view, you must implement a virtual view hierarchy by overriding getAccessibilityNodeProvider() in your custom view in order to be compatible with accessibility services.
version: 注:如果您的自定义视图具有明显的可点击区域,如自定义日历视图,在你自定义视图中，为了兼容辅助性服务，必须通过重写getAccessibilityNodeProvider()实现一个虚拟视图层。

测试辅助功能 Testing Accessibility

original: Testing the accessibility of your application is an important part of ensuring your users have a great experience. You can test the most important accessibility features by using your application with audible feedback enabled and navigating within your application using only directional controls. For more information on testing accessibility in your application, see the Accessibility Testing Checklist.
version: 测试你应用程序的辅助功能是确保良好用户经验的一个重要组成部分。你可以启用声音反馈，在应用中只使用方向控制来测试你应用中最重要的辅助性特征。更多在应用程序中辅助性测试信息,请参阅辅助性测试清单一节。

注：原文出自：http://developer.android.com/guide/topics/ui/accessibility/apps.html#test
注：译文出自：http://blog.csdn.net/gtsong/article/details/10285993#t13

示例代码关于View回调

@ViewInject(id = R.id.tv_onekey) TextView iv_call;

iv_call.setAccessibilityDelegate(new View.AccessibilityDelegate(){
@Override
public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) {
super.onInitializeAccessibilityEvent(host, event);
//焦点进入所在的view
if(event.getEventType() == AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED){
sCategory=”dial”;
bIfSendRecognition=true;
}
//焦点离开所在的view
else if(event.getEventType() == AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED){
bIfSendRecognition=false;
}
}
});