这篇文章主要介绍“Android无障碍服务performAction怎么调用”，在日常操作中，相信很多人在Android无障碍服务performAction怎么调用问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”Android无障碍服务performAction怎么调用”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
无障碍服务可以模拟一些用户操作，无障碍可以处理的对象，通过类 AccessibilityNodeInfo 表示，通过无障碍服务，可以通过它的 performAction 方法来触发一些 action ，包括：
ACTION_FOCUS // 获取焦点ACTION_CLEAR_FOCUS // 清除焦点ACTION_SELECT // 选中ACTION_CLEAR_SELECTION // 清除选中状态ACTION_ACCESSIBILITY_FOCUS // 无障碍焦点ACTION_CLEAR_ACCESSIBILITY_FOCUS // 清除无障碍焦点ACTION_CLICK // 点击ACTION_LONG_CLICK // 长按ACTION_NEXT_AT_MOVEMENT_GRANULARITY // 下一步移动ACTION_PREVIOUS_AT_MOVEMENT_GRANULARITY // 上一步移动ACTION_NEXT_HTML_ELEMENT // 下一个 html 元素ACTION_PREVIOUS_HTML_ELEMENT // 上一个 html 元素ACTION_SCROLL_FORWARD // 向前滑动ACTION_SCROLL_BACKWARD // 向后滑动他们都可以通过performAction方法进行处理：
// in AccessibilityNodeInfopublic boolean performAction(int action) { enforceSealed(); if (!canPerformRequestOverConnection(mConnectionId, mWindowId, mSourceNodeId)) { return false; } AccessibilityInteractionClient client = AccessibilityInteractionClient.getInstance(); return client.performAccessibilityAction(mConnectionId, mWindowId, mSourceNodeId, action, null);}在这个方法中，第一步是检查 perform 是否可以通过 connection 请求，这里 connection 检查是根据通过 binder 通信传递过来的 id 检查连接是否正常。 然后通过AccessibilityInteractionClient对象，调用它的performAccessibilityAction方法去进行实际操作的。
AccessibilityInteractionClient
这个类是一个执行可访问性交互的单例，它可以根据 View 的快照查询远程的 View 层次结构，以及通过 View 层次结构，来请求对 View 执行某项操作。
基本原理：内容检索 API 从客户端的角度来看是同步的，但在内部它们是异步的。客户端线程调用系统请求操作并提供回调以接收结果，然后等待该结果的超时。系统强制执行安全性并将请求委托给给定的视图层次结构， 在该视图层次结构中发布消息（来自 Binder 线程），描述 UI 线程要执行的内容，其结果是通过上述回调传递的。但是，被阻塞的客户端线程和目标视图层次结构的主 UI 线程可以是同一个线程，例如无障碍服务和 Activity 在同一个进程中运行，因此它们在同一个主线程上执行。 在这种情况下，检索将会失败，因为 UI 线程在等待检索结果，会导致阻塞。 为了避免在进行调用时出现这种情况，客户端还会传递其进程和线程 ID，以便访问的视图层次结构可以检测发出请求的客户端是否正在其主 UI 线程中运行。 在这种情况下，视图层次结构，特别是对它执行 IPC 的绑定线程，不会发布要在 UI 线程上运行的消息，而是将其传递给单例交互客户端，通过该客户端发生所有交互，后者负责执行开始等待通过回调传递的异步结果之前的消息。在这种情况下，已经收到预期的结果，因此不执行等待。
上面是官方备注的描述，大概意思最好不要在主线程执行检索操作。
继续跟进它的performAccessibilityAction方法：
public boolean performAccessibilityAction(int connectionId, int accessibilityWindowId, long accessibilityNodeId, int action, Bundle arguments) { try { IAccessibilityServiceConnection connection = getConnection(connectionId); if (connection != null) { final int interactionId = mInteractionIdCounter.getAndIncrement(); final long identityToken = Binder.clearCallingIdentity(); final boolean success; try { success = connection.performAccessibilityAction( accessibilityWindowId, accessibilityNodeId, action, arguments, interactionId, this, Thread.currentThread().getId()); // 【*】 } finally { Binder.restoreCallingIdentity(identityToken); } if (success) { return getPerformAccessibilityActionResultAndClear(interactionId); } } } catch (RemoteException re) { Log.w(LOG_TAG, "Error while calling remote performAccessibilityAction", re); } return false; }这里通过 getConnection(connectionId) 获取了一个 IAccessibilityServiceConnection 。
public static IAccessibilityServiceConnection getConnection(int connectionId) { synchronized (sConnectionCache) { return sConnectionCache.get(connectionId); }}这里的 sConnectionCache 通过 AccessibilityInteractionClient 的addConnection添加数据的，addConnection在 AccessbilityService 创建初始化时调用的：
case DO_INIT: { mConnectionId = message.arg1; SomeArgs args = (SomeArgs) message.obj; IAccessibilityServiceConnection connection = (IAccessibilityServiceConnection) args.arg1; IBinder windowToken = (IBinder) args.arg2; args.recycle(); if (connection != null) { AccessibilityInteractionClient.getInstance(mContext).addConnection(mConnectionId, connection); mCallback.init(mConnectionId, windowToken); mCallback.onServiceConnected(); } else { AccessibilityInteractionClient.getInstance(mContext).removeConnection(mConnectionId); mConnectionId = AccessibilityInteractionClient.NO_ID; AccessibilityInteractionClient.getInstance(mContext).clearCache(); mCallback.init(AccessibilityInteractionClient.NO_ID, null); } return;}也就是说，在 AccessbilityService 创建时，会将一个表示连接的对象存到 AccessibilityInteractionClient 的连接缓存中。
IAccessibilityServiceConnection
它是 AccessibilityManagerService 向 AccessbilityService 暴露的 AIDL 接口，提供给 AccessbilityService 调用AccessibilityManagerService 的能力。 上面的 performAction 流程中，调用到了 connection 的performAccessibilityAction方法。 而 IAccessibilityServiceConnection 有两个实现类，AccessibilityServiceConnectionImpl和AbstractAccessibilityServiceConnection，前者都是空实现，显然不是我们要调用到的地方，后者的performAccessibilityAction：
@Overridepublic boolean performAccessibilityAction(int accessibilityWindowId, long accessibilityNodeId, int action, Bundle arguments, int interactionId, IAccessibilityInteractionConnectionCallback callback, long interrogatingTid) throws RemoteException { final int resolvedWindowId; synchronized (mLock) { if (!hasRightsToCurrentUserLocked()) { return false; } resolvedWindowId = resolveAccessibilityWindowIdLocked(accessibilityWindowId); if (!mSecurityPolicy.canGetAccessibilityNodeInfoLocked( mSystemSupport.getCurrentUserIdLocked(), this, resolvedWindowId)) { return false; } } if (!mSecurityPolicy.checkAccessibilityAccess(this)) { return false; } return performAccessibilityActionInternal( mSystemSupport.getCurrentUserIdLocked(), resolvedWindowId, accessibilityNodeId, action, arguments, interactionId, callback, mFetchFlags, interrogatingTid);}最后的一行调用：
private boolean performAccessibilityActionInternal(int userId, int resolvedWindowId, long accessibilityNodeId, int action, Bundle arguments, int interactionId, IAccessibilityInteractionConnectionCallback callback, int fetchFlags, long interrogatingTid) { RemoteAccessibilityConnection connection; IBinder activityToken = null; // 同步获取 connection synchronized (mLock) { connection = mA11yWindowManager.getConnectionLocked(userId, resolvedWindowId); if (connection == null) { return false; } final boolean isA11yFocusAction = (action == ACTION_ACCESSIBILITY_FOCUS) || (action == ACTION_CLEAR_ACCESSIBILITY_FOCUS); if (!isA11yFocusAction) { final WindowInfo windowInfo = mA11yWindowManager.findWindowInfoByIdLocked(resolvedWindowId); if (windowInfo != null) activityToken = windowInfo.activityToken; } final AccessibilityWindowInfo a11yWindowInfo = mA11yWindowManager.findA11yWindowInfoByIdLocked(resolvedWindowId); if (a11yWindowInfo != null && a11yWindowInfo.isInPictureInPictureMode() && mA11yWindowManager.getPictureInPictureActionReplacingConnection() != null && !isA11yFocusAction) { connection = mA11yWindowManager.getPictureInPictureActionReplacingConnection(); } } // 通过 connection 调用到远程服务的performAccessibilityAction final int interrogatingPid = Binder.getCallingPid(); final long identityToken = Binder.clearCallingIdentity(); try { // 无论操作是否成功，它都是由用户操作的无障碍服务生成的，因此请注意用户Activity。 mPowerManager.userActivity(SystemClock.uptimeMillis(), PowerManager.USER_ACTIVITY_EVENT_ACCESSIBILITY, 0); if (action == ACTION_CLICK || action == ACTION_LONG_CLICK) { mA11yWindowManager.notifyOutsideTouch(userId, resolvedWindowId); } if (activityToken != null) { LocalServices.getService(ActivityTaskManagerInternal.class).setFocusedActivity(activityToken); } connection.getRemote().performAccessibilityAction(accessibilityNodeId, action, arguments, interactionId, callback, fetchFlags, interrogatingPid, interrogatingTid); } catch (RemoteException re) { if (DEBUG) { Slog.e(LOG_TAG, "Error calling performAccessibilityAction: " + re); } return false; } finally { Binder.restoreCallingIdentity(identityToken); } return true; }在这个方法中，通过 connection 调用到了远端的 performAccessibilityAction 方法。
关键的一行是：
connection.getRemote().performAccessibilityAction(accessibilityNodeId, action, arguments, interactionId, callback, fetchFlags, interrogatingPid, interrogatingTid);这里的 connection 类型定义成了RemoteAccessibilityConnection。
RemoteAccessibilityConnection
RemoteAccessibilityConnection 是AccessibilityWindowManager的内部类，它的getRemote()返回类型是IAccessibilityInteractionConnection。
AccessibilityWindowManager
此类为 AccessibilityManagerService 提供 API 来管理 AccessibilityWindowInfo 和 WindowInfos。
IAccessibilityInteractionConnection
这是一个 AIDL 中定义的接口，用来进行 给定 window 中 AccessibilityManagerService 和 ViewRoot 之间交互的接口。
也就是说getRemote(). performAccessibilityAction(...)最终来到了 ViewRootImpl 中。
AccessibilityInteractionConnection
ViewRootImpl 中存在一个内部类AccessibilityInteractionConnection，它是这个 ViewAncestor 提供给 AccessibilityManagerService 的一个接口，后者可以与这个 ViewAncestor 中的视图层次结构进行交互。
它的performAccessibilityAction实现是：
@Overridepublic void performAccessibilityAction(long accessibilityNodeId, int action, Bundle arguments, int interactionId, IAccessibilityInteractionConnectionCallback callback, int flags, int interrogatingPid, long interrogatingTid) { ViewRootImpl viewRootImpl = mViewRootImpl.get(); if (viewRootImpl != null && viewRootImpl.mView != null) { viewRootImpl.getAccessibilityInteractionController().performAccessibilityActionClientThread(accessibilityNodeId, action, arguments, interactionId, callback, flags, interrogatingPid, interrogatingTid); } else { // We cannot make the call and notify the caller so it does not wait. try { callback.setPerformAccessibilityActionResult(false, interactionId); } catch (RemoteException re) { } }}内部又是通过代理调用 ，ViewRootImpl 的 getAccessibilityInteractionController() 返回了一个 AccessibilityInteractionController 对象。
AccessibilityInteractionController
它的 performAccessibilityActionClientThread :
public void performAccessibilityActionClientThread(long accessibilityNodeId, int action, Bundle arguments, int interactionId, IAccessibilityInteractionConnectionCallback callback, int flags, int interrogatingPid, long interrogatingTid) { Message message = mHandler.obtainMessage(); message.what = PrivateHandler.MSG_PERFORM_ACCESSIBILITY_ACTION; message.arg1 = flags; message.arg2 = AccessibilityNodeInfo.getAccessibilityViewId(accessibilityNodeId); SomeArgs args = SomeArgs.obtain(); args.argi1 = AccessibilityNodeInfo.getVirtualDescendantId(accessibilityNodeId); args.argi2 = action; args.argi3 = interactionId; args.arg1 = callback; args.arg2 = arguments; message.obj = args; scheduleMessage(message, interrogatingPid, interrogatingTid, CONSIDER_REQUEST_PREPARERS);}组装了一个 message ，并通过 scheduleMessage 方法去执行：
private void scheduleMessage(Message message, int interrogatingPid, long interrogatingTid, boolean ignoreRequestPreparers) { if (ignoreRequestPreparers || !holdOffMessageIfNeeded(message, interrogatingPid, interrogatingTid)) { if (interrogatingPid == mMyProcessId && interrogatingTid == mMyLooperThreadId && mHandler.hasAccessibilityCallback(message)) { AccessibilityInteractionClient.getInstanceForThread( interrogatingTid).setSameThreadMessage(message); } else { if (!mHandler.hasAccessibilityCallback(message) && Thread.currentThread().getId() == mMyLooperThreadId) { mHandler.handleMessage(message); } else { mHandler.sendMessage(message); } } }}这里实际上，如果是在主线程，则处理消息，如果不是，则发送消息到主线程处理。handler 的类型是 PrivateHandler ，在 AccessibilityInteractionController 内部定义。
它的处理消息方法的实现是：
@Overridepublic void handleMessage(Message message) { final int type = message.what; switch (type) { // ... case MSG_PERFORM_ACCESSIBILITY_ACTION: { performAccessibilityActionUiThread(message); } break; // ... default: throw new IllegalArgumentException("Unknown message type: " + type); }}执行到了 performAccessibilityActionUiThread(message); :
private void performAccessibilityActionUiThread(Message message) { // ... boolean succeeded = false; try { // ... final View target = findViewByAccessibilityId(accessibilityViewId); if (target != null && isShown(target)) { mA11yManager.notifyPerformingAction(action); if (action == R.id.accessibilityActionClickOnClickableSpan) { // 单独处理这个 hidden action succeeded = handleClickableSpanActionUiThread(target, virtualDescendantId, arguments); } else { AccessibilityNodeProvider provider = target.getAccessibilityNodeProvider(); if (provider != null) { succeeded = provider.performAction(virtualDescendantId, action, arguments); } else if (virtualDescendantId == AccessibilityNodeProvider.HOST_VIEW_ID) { succeeded = target.performAccessibilityAction(action, arguments); } } mA11yManager.notifyPerformingAction(0); } } finally { try { mViewRootImpl.mAttachInfo.mAccessibilityFetchFlags = 0; callback.setPerformAccessibilityActionResult(succeeded, interactionId); } catch (RemoteException re) { } } }在这个流程中，分为三种情况去真正执行 performAction ：
1. action == R.id.accessibilityActionClickOnClickableSpan
private boolean handleClickableSpanActionUiThread( View view, int virtualDescendantId, Bundle arguments) { Parcelable span = arguments.getParcelable(ACTION_ARGUMENT_ACCESSIBLE_CLICKABLE_SPAN); if (!(span instanceof AccessibilityClickableSpan)) { return false; } // Find the original ClickableSpan if it's still on the screen AccessibilityNodeInfo infoWithSpan = null; AccessibilityNodeProvider provider = view.getAccessibilityNodeProvider(); if (provider != null) { infoWithSpan = provider.createAccessibilityNodeInfo(virtualDescendantId); } else if (virtualDescendantId == AccessibilityNodeProvider.HOST_VIEW_ID) { infoWithSpan = view.createAccessibilityNodeInfo(); } if (infoWithSpan == null) { return false; } // Click on the corresponding span ClickableSpan clickableSpan = ((AccessibilityClickableSpan) span).findClickableSpan( infoWithSpan.getOriginalText()); if (clickableSpan != null) { clickableSpan.onClick(view); return true; } return false;}2. View. AccessibilityNodeProvider != null
当能够通过 View 获取到 AccessibilityNodeProvider 对象是，通过它的 performAction 方法，去执行真正的调用，它的真正调用在 AccessibilityNodeProviderCompat中，这个 Compat 的实现在ExploreByTouchHelper中的内部类MyNodeProvider中：
@Overridepublic boolean performAction(int virtualViewId, int action, Bundle arguments) { return ExploreByTouchHelper.this.performAction(virtualViewId, action, arguments);}在 ExploreByTouchHelper 中继续查看：
boolean performAction(int virtualViewId, int action, Bundle arguments) { switch (virtualViewId) { case HOST_ID: return performActionForHost(action, arguments); default: return performActionForChild(virtualViewId, action, arguments); }}private boolean performActionForHost(int action, Bundle arguments) { return ViewCompat.performAccessibilityAction(mHost, action, arguments);}private boolean performActionForChild(int virtualViewId, int action, Bundle arguments) { switch (action) { case AccessibilityNodeInfoCompat.ACTION_ACCESSIBILITY_FOCUS: return requestAccessibilityFocus(virtualViewId); case AccessibilityNodeInfoCompat.ACTION_CLEAR_ACCESSIBILITY_FOCUS: return clearAccessibilityFocus(virtualViewId); case AccessibilityNodeInfoCompat.ACTION_FOCUS: return requestKeyboardFocusForVirtualView(virtualViewId); case AccessibilityNodeInfoCompat.ACTION_CLEAR_FOCUS: return clearKeyboardFocusForVirtualView(virtualViewId); default: return onPerformActionForVirtualView(virtualViewId, action, arguments); }}前者调用到了 ViewCompat :
public static boolean performAccessibilityAction(@NonNull View view, int action, Bundle arguments) { if (Build.VERSION.SDK_INT >= 16) { return view.performAccessibilityAction(action, arguments); } return false;}然后是 View 的 ：
public boolean performAccessibilityAction(int action, Bundle arguments) { if (mAccessibilityDelegate != null) { return mAccessibilityDelegate.performAccessibilityAction(this, action, arguments); } else { return performAccessibilityActionInternal(action, arguments); }}mAccessibilityDelegate.performAccessibilityAction的实现是：
public boolean performAccessibilityAction(View host, int action, Bundle args) { return host.performAccessibilityActionInternal(action, args);}也是调用到了 View 的performAccessibilityActionInternal 。 performAccessibilityActionInternal 的实现是：
// in View.javapublic boolean performAccessibilityActionInternal(int action, Bundle arguments) { if (isNestedScrollingEnabled() && (action == AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD || action == AccessibilityNodeInfo.ACTION_SCROLL_FORWARD || action == R.id.accessibilityActionScrollUp || action == R.id.accessibilityActionScrollLeft || action == R.id.accessibilityActionScrollDown || action == R.id.accessibilityActionScrollRight)) { if (dispatchNestedPrePerformAccessibilityAction(action, arguments)) { return true; } } switch (action) { case AccessibilityNodeInfo.ACTION_CLICK: { if (isClickable()) { performClickInternal(); return true; } } break; case AccessibilityNodeInfo.ACTION_LONG_CLICK: { if (isLongClickable()) { performLongClick(); return true; } } break; // ... } return false;}以 AccessibilityNodeInfo.ACTION_CLICK 为例，内部调用是：
private boolean performClickInternal() { // Must notify autofill manager before performing the click actions to avoid scenarios where // the app has a click listener that changes the state of views the autofill service might // be interested on. notifyAutofillManagerOnClick(); return performClick();}这样就调用到了 View 的点击事件。
3. View. AccessibilityNodeProvider == null && virtualDescendantId == AccessibilityNodeProvider.HOST_VIEW_ID
target.performAccessibilityAction(action, arguments);这里 target 是个 View， 也是走的 View 的 performAccessibilityAction ，和上面流程一样。
View 的 performClick 方法是同步的还是异步的？
public boolean performClick() { // We still need to call this method to handle the cases where performClick() was called // externally, instead of through performClickInternal() notifyAutofillManagerOnClick(); final boolean result; final ListenerInfo li = mListenerInfo; if (li != null && li.mOnClickListener != null) { playSoundEffect(SoundEffectConstants.CLICK); li.mOnClickListener.onClick(this); result = true; } else { result = false; } sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED); notifyEnterOrExitForAutoFillIfNeeded(true); return result;}同步的。
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