无障碍AccessibilityService基本用法

一、背景

????本文仅用于做学习总结，转换成自己的理解，方便需要时快速查阅，深入研究可以去官网了解更多：官网链接点这里
????之前对接AI语音功能时，发现有些按钮（或文本）在我没有主动注册唤醒词场景下，还是响应了点击，使用profiler跟踪调用堆栈才发现是使用了无障碍服务实现的。因为开发的是系统应用，也没必要主动去打开无障碍服务开关，于是觉得无障碍服务有很大的可发挥空间，于是借助无障碍服务，实现了一个显示当前展示的Window/Activity/Dialog的悬浮窗，用于演示无障碍服务的用法及其强大之处。

二、用法

2.1 新建一个继承AccessibilityService的无障碍服务类，并按需重写回调方法

class AccessibilityTest : AccessibilityService() {
    override fun onAccessibilityEvent(event: AccessibilityEvent?) {
        Log.d(TAG, "onAccessibilityEvent: event = $event")
    }

    override fun onServiceConnected() {
        super.onServiceConnected()
        Log.d(TAG, "onServiceConnected: ")
    }
    
    override fun onUnbind(intent: Intent?): Boolean {
        Log.d(TAG, "onUnbind: intent = $intent")
        return super.onUnbind(intent)
    }

    override fun onInterrupt() {
        Log.d(TAG, "onInterrupt: ")
    }
}

• onServiceConnected():
  ????当无障碍服务打开后，有注册的交互事件发生时，如果还没有连接服务，这会先执行连接，并回调这个方法。
  ????问题：AccessibilityServie继承Service也就是普通的服务，没有绑定前台的notification等可见的界面，会不会在后台过一会儿就断开了，是否会导致某些时候无法捕获到交互的事件？？
• onAccessibilityEvent(event: AccessibilityEvent?):
  ????当有注册的交互事件，比如：点击、长按、焦点变化等触发时，会回调这个函数
  • event.getEventType(): 获取事件类型，点击：TYPE_VIEW_CLICKED，长按：TYPE_VIEW_LONG_CLICKED，窗口状态变化：TYPE_WINDOW_STATE_CHANGED，详细的可以查阅AccessibilityService类的EventType注解中有枚举出所有的事件类型。
  • event.getPackName(): 获取交互来自的包名
  • event.getClassName(): 如果是Activity/Dialog则是其类的全路径名，如果是View的话则展示当前的View全路径名。
• onUnbind(intent: Intent?):
  ????断开服务时回调，用于处理一些资源释放的逻辑。
• onInterrupt():

2.2 AndroidManifest.xml文件中注册无障碍服务

????这个步骤和普通的Service注册有些不同，需要配置permission、intent-filter和无障碍服务的xml配置文件，基本都是固定的格式，只是按需改一些配置项。

<service
    android:name=".accessibility.AccessibilityTest"
    android:exported="true"
    android:label="@string/accessibility_tip"
    android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE"
    android:process=":BackgroundService">
    <intent-filter>
        <action android:name="android.accessibilityservice.AccessibilityService" />
    </intent-filter>
    <meta-data
        android:name="android.accessibilityservice"
        android:resource="@xml/accessibility_config" />
</service>

• service节点配置的label标签会在无障碍服务中展示，比如上面的label内容是“accessibility_tip”，那么在无障碍服务中展示就会如下所示“：
  
  
  ????在/res/xml目录下，新建一个accessibility_config.xml文件，内容如下：

<?xml version="1.0" encoding="utf-8"?>
<accessibility-service xmlns:android="http://schemas.android.com/apk/res/android"
    android:accessibilityEventTypes="typeAllMask"
    android:accessibilityFeedbackType="feedbackGeneric"
    android:canRetrieveWindowContent="true"
    android:description="@string/accessibilty_desc" />

??：如果这里指定了包名（android:packageNames的值，多个包名用英文逗号分隔。）则只会收到对应包名应用的事件。

• android:description属性设置的就是上面的无障碍中accessibility_tip服务最下面的文案介绍。
• android:accessibilityEventTypes：指定接收的事件类型
• android:accessibilityFeedbackType：指定接收的反馈类型

2.3 在AccessibilityTest的onServiceConnected方法中动态设置serviceInfo

• AccessibilityTest->onServiceConnected(): 通过在Service连接到无障碍服务的回调，调用setServiceInfo方法，可以在在运行时调整无障碍服务的配置：

override fun onServiceConnected() {
    super.onServiceConnected()
    Log.d(TAG, "onServiceConnected: ")
    val accessibilityServiceInfo = AccessibilityServiceInfo()
    accessibilityServiceInfo.eventTypes = (AccessibilityEvent.TYPE_WINDOWS_CHANGED
            or AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED
            or AccessibilityEvent.TYPE_VIEW_CLICKED
            or AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED
            or AccessibilityEvent.TYPE_NOTIFICATION_STATE_CHANGED)
    accessibilityServiceInfo.feedbackType = AccessibilityServiceInfo.FEEDBACK_ALL_MASK
    accessibilityServiceInfo.notificationTimeout = 0
    accessibilityServiceInfo.flags = AccessibilityServiceInfo.DEFAULT
    // 如果这里指定了包名则只会收到对应包名应用的事件
      accessibilityServiceInfo.packageNames = arrayOf("com.yanggui.animatortest")
    serviceInfo = accessibilityServiceInfo
}

????完成以上的步骤，然后编译运行安装到手机上，然后从无障碍服务中开启，就能够在AccessibilityTest的onAccessibilityEvent中收到各种交互事件了。

无障碍服务跑起来后，会打印如下log：

// 从无障碍服务中打开accessibility_tip服务回调onServiceConnected方法：
14:25:34.170  D  onServiceConnected:
// 打开当前应用会执行onAccessibilityEvent方法，回调一系列的事件信息，封装在// AccessibilityEvent中
14:26:44.792  D  onAccessibilityEvent: event = EventType: TYPE_VIEW_CLICKED; EventTime: 7897173; PackageName: com.google.android.apps.nexuslauncher; MovementGranularity: 0; Action: 0; ContentChangeTypes: []; WindowChangeTypes: [] [ ClassName: android.widget.TextView; Text: [AnimatorTest]; ContentDescription: AnimatorTest; ItemCount: -1; CurrentItemIndex: -1; Enabled: true; Password: false; Checked: false; FullScreen: false; Scrollable: false; BeforeText: null; FromIndex: -1; ToIndex: -1; ScrollX: 0; ScrollY: 0; MaxScrollX: 0; MaxScrollY: 0; ScrollDeltaX: -1; ScrollDeltaY: -1; AddedCount: -1; RemovedCount: -1; ParcelableData: null ]; recordCount: 0
14:26:44.847  D  onAccessibilityEvent: event = EventType: TYPE_WINDOW_CONTENT_CHANGED; EventTime: 7897231; PackageName: com.google.android.apps.nexuslauncher; MovementGranularity: 0; Action: 0; ContentChangeTypes: [CONTENT_CHANGE_TYPE_SUBTREE]; WindowChangeTypes: [] [ ClassName: android.widget.FrameLayout; Text: []; ContentDescription: null; ItemCount: -1; CurrentItemIndex: -1; Enabled: true; Password: false; Checked: false; FullScreen: false; Scrollable: false; BeforeText: null; FromIndex: -1; ToIndex: -1; ScrollX: 0; ScrollY: 0; MaxScrollX: 0; MaxScrollY: 0; ScrollDeltaX: -1; ScrollDeltaY: -1; AddedCount: -1; RemovedCount: -1; ParcelableData: null ]; recordCount: 0
14:26:44.891  D  onAccessibilityEvent: event = EventType: TYPE_WINDOW_STATE_CHANGED; EventTime: 7897277; PackageName: com.yanggui.animatortest; MovementGranularity: 0; Action: 0; ContentChangeTypes: []; WindowChangeTypes: [] [ ClassName: com.yanggui.animatortest.leanback.RowsSupportFragmentActivity; Text: [AnimatorTest]; ContentDescription: null; ItemCount: -1; CurrentItemIndex: -1; Enabled: true; Password: false; Checked: false; FullScreen: true; Scrollable: false; BeforeText: null; FromIndex: -1; ToIndex: -1; ScrollX: 0; ScrollY: 0; MaxScrollX: 0; MaxScrollY: 0; ScrollDeltaX: -1; ScrollDeltaY: -1; AddedCount: -1; RemovedCount: -1; ParcelableData: null ]; recordCount: 0
14:26:44.952  D  onAccessibilityEvent: event = EventType: TYPE_WINDOW_STATE_CHANGED; EventTime: 7897337; PackageName: com.yanggui.animatortest; MovementGranularity: 0; Action: 0; ContentChangeTypes: []; WindowChangeTypes: [] [ ClassName: com.yanggui.animatortest.leanback.RowsSupportFragmentActivity; Text: [AnimatorTest]; ContentDescription: null; ItemCount: -1; CurrentItemIndex: -1; Enabled: true; Password: false; Checked: false; FullScreen: true; Scrollable: false; BeforeText: null; FromIndex: -1; ToIndex: -1; ScrollX: 0; ScrollY: 0; MaxScrollX: 0; MaxScrollY: 0; ScrollDeltaX: -1; ScrollDeltaY: -1; AddedCount: -1; RemovedCount: -1; ParcelableData: null ]; recordCount: 0
// 从无障碍服务中关闭accessibility_tip服务回调onUnbind方法：
14:24:38.264  D  onUnbind: intent = Intent { cmp=com.yanggui.animatortest/.accessibility.AccessibilityTest }

2.4 附：反馈类型（feedbackType）和事件类型（eventType）的枚举值

• 反馈类型（feedbackType）：定义在AccessibilityServiceInfo中

@IntDef(flag = true, prefix = { "FEEDBACK_" }, value = {
        FEEDBACK_AUDIBLE,
        FEEDBACK_GENERIC,
        FEEDBACK_HAPTIC,
        FEEDBACK_SPOKEN,
        FEEDBACK_VISUAL,
        FEEDBACK_BRAILLE
})
@Retention(RetentionPolicy.SOURCE)
public @interface FeedbackType {}

• 事件类型（eventType）：定义在AccessibilityEvent中

@IntDef(
      flag = true,
      prefix = {"TYPE_"},
      value = {
           TYPE_VIEW_CLICKED, // 点击事件
           TYPE_VIEW_LONG_CLICKED, // 长按事件
           TYPE_VIEW_SELECTED, // view选中
           TYPE_VIEW_FOCUSED, // view上焦，使用遥控操作的需要关注该事件
           TYPE_VIEW_TEXT_CHANGED, // 表示更改 android.widget.EditText的文本的事件。
           TYPE_WINDOW_STATE_CHANGED,
           TYPE_NOTIFICATION_STATE_CHANGED,
           TYPE_VIEW_HOVER_ENTER,
           TYPE_VIEW_HOVER_EXIT,
           TYPE_TOUCH_EXPLORATION_GESTURE_START,
           TYPE_TOUCH_EXPLORATION_GESTURE_END,
           TYPE_WINDOW_CONTENT_CHANGED,
           TYPE_VIEW_SCROLLED,
           TYPE_VIEW_TEXT_SELECTION_CHANGED,
           TYPE_ANNOUNCEMENT,
           TYPE_VIEW_ACCESSIBILITY_FOCUSED,
           TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED,
           TYPE_VIEW_TEXT_TRAVERSED_AT_MOVEMENT_GRANULARITY,
           TYPE_GESTURE_DETECTION_START,
           TYPE_GESTURE_DETECTION_END,
           TYPE_TOUCH_INTERACTION_START,
           TYPE_TOUCH_INTERACTION_END,
           TYPE_WINDOWS_CHANGED,
           TYPE_VIEW_CONTEXT_CLICKED,
           TYPE_ASSIST_READING_CONTEXT,
           TYPE_SPEECH_STATE_CHANGE
    })
    @Retention(RetentionPolicy.SOURCE)
    public @interface EventType {}

三、实现展示当前Activity/Dialog/Window信息的悬浮窗

????如上介绍的，无障碍服务是能够获取到各种交互事件，从onAccessibilityEvent回调中可轻松拿到交互控件的packageName和className，所以基于无障碍服务能力的支持，也就很容易实现悬浮展示当前Activity的功能了。

3.1 全局悬浮窗的实现

• 这个业务点的关键知识点是能全局悬浮，且不依赖Activity类型context，也就是不需要windowToken参数的window类型。

private const val TAG = "TopActivityEvent"
class TopActivityEventWindow {
    companion object {
        @SuppressLint("StaticFieldLeak")
        private var rootView: View? = null

        @SuppressLint("StaticFieldLeak")
        private var tvContent: TextView? = null

        @SuppressLint("StaticFieldLeak")
        private var window: TopActivityEventWindow? = null

        @SuppressLint("StaticFieldLeak")
        fun showEvent(ctx: Context, pkgName: String?, activityClassName: String?) {
            if (window == null) {
                initEventWindow(ctx)
            }
            if (!pkgName.isNullOrBlank() && !activityClassName.isNullOrBlank()) {
                tvContent?.text = "$pkgName\n$activityClassName"
            } else {
                Log.e(TAG, "showEvent: pkgName = $pkgName, activityClassName = $activityClassName")
            }
        }

        private fun initEventWindow(ctx: Context) {
            rootView =
                LayoutInflater.from(ctx).inflate(R.layout.layout_top_activity_window, null, false)
            val windowManager = ctx.getSystemService(Context.WINDOW_SERVICE) as? WindowManager
            windowManager?.apply {
                val lp = WindowManager.LayoutParams(
                    WindowManager.LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.WRAP_CONTENT
                )
                lp.type = if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.N) {
                    WindowManager.LayoutParams.TYPE_TOAST
                } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
                    // android31及以上 需要使用TYPE_APPLICATION_OVERLAY才能展示，使用ALERT_WINDOW会报没有权限
                    WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY
                } else {
                    WindowManager.LayoutParams.TYPE_SYSTEM_ALERT
                }
                lp.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE or WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
                lp.gravity = Gravity.TOP or Gravity.LEFT
                lp.format = PixelFormat.TRANSLUCENT
                addView(rootView, lp)
            }
            tvContent = rootView?.findViewById(R.id.top_activity_window_text)
            window = TopActivityEventWindow()
        }

        fun dismiss(ctx: Context) {
            if (window != null) {
                val windowManager = ctx.getSystemService(Context.WINDOW_SERVICE) as? WindowManager
                windowManager?.removeView(rootView)
                tvContent = null
                rootView = null
                window = null
            }
        }
    }
}

3.1 在无障碍服务的onAccessibilityEvent中调用悬浮窗的展示逻辑

override fun onAccessibilityEvent(event: AccessibilityEvent?) {
        Log.d(TAG, "onAccessibilityEvent: event = $event")
        if (event?.eventType == AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED) {
            TopActivityEventWindow.showEvent(
                this.applicationContext, "${event.packageName}", "${event.className}"
            )
        }
    }

3.2 实现的实际效果

• 捕获pixel3a-api33模拟器的Launcher展示效果：
  
• 自己的demo app的主页获取效果：
  
• Dialog的捕获效果：
  
• PopupWindow获取不到待解决！！