public class AutoDismissService extends AccessibilityService { @Override public void onAccessibilityEvent(AccessibilityEvent event) { if (event == null) { return; }  // 自動將android系統(tǒng)彈出的其它crash dialog取消 dismissAppErrorDialogIfExists(event); }  private void dismissAppErrorDialogIfExists(AccessibilityEvent event) { // WINDOW視圖變化才進行對應(yīng)操作 if ((event.getEventType() == AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED && event.getPackageName().equals("android")) { // 查找?guī)в?OK"字符的可點擊Node AccessibilityNodeInfo nodeInfo = findViewByText("OK", true); if (nodeInfo != null) { // 查找到后執(zhí)行點擊操作 performViewClick(nodeInfo); } } public AccessibilityNodeInfo findViewByText(String text, boolean clickable) { // 獲取當(dāng)前窗口父節(jié)點 AccessibilityNodeInfo accessibilityNodeInfo = getRootInActiveWindow(); if (accessibilityNodeInfo == null) { return null; } // 獲取到滿足字符要求的節(jié)點 List<AccessibilityNodeInfo> nodeInfoList = accessibilityNodeInfo.findAccessibilityNodeInfosByText(text); if (nodeInfoList != null && !nodeInfoList.isEmpty()) { for (AccessibilityNodeInfo nodeInfo : nodeInfoList) { if (nodeInfo != null && (nodeInfo.isClickable() == clickable)) {  return nodeInfo; } } } return null; }  public void performViewClick(AccessibilityNodeInfo nodeInfo) { if (nodeInfo == null) { return; } // 由下至上進行查詢，直到尋找到可點擊的節(jié)點 while (nodeInfo != null) { if (nodeInfo.isClickable()) { nodeInfo.performAction(AccessibilityNodeInfo.ACTION_CLICK); break; } nodeInfo = nodeInfo.getParent(); } }}

private void setText(CharSequence text, BufferType type,   boolean notifyBefore, int oldlen) { ... notifyViewAccessibilityStateChangedIfNeeded(AccessibilityEvent.CONTENT_CHANGE_TYPE_TEXT); ...   }public void notifyViewAccessibilityStateChangedIfNeeded(int changeType) { if (!AccessibilityManager.getInstance(mContext).isEnabled() || mAttachInfo == null) { return; } if (mSendViewStateChangedAccessibilityEvent == null) { // 本質(zhì)上是一個Runnable，意味著這里的流程會進入異步處理 mSendViewStateChangedAccessibilityEvent =  new SendViewStateChangedAccessibilityEvent(); } mSendViewStateChangedAccessibilityEvent.runOrPost(changeType);}private class SendViewStateChangedAccessibilityEvent implements Runnable { ... @Override public void run() { mPosted = false; mPostedWithDelay = false; mLastEventTimeMillis = SystemClock.uptimeMillis(); if (AccessibilityManager.getInstance(mContext).isEnabled()) {  final AccessibilityEvent event = AccessibilityEvent.obtain();  event.setEventType(AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);  event.setContentChangeTypes(mChangeTypes);  // 最終TYPE_WINDOW_CONTENT_CHANGED事件在這里異步發(fā)送  sendAccessibilityEventUnchecked(event); } mChangeTypes = 0; } ...}public void sendAccessibilityEventUnchecked(AccessibilityEvent event) { if (mAccessibilityDelegate != null) { mAccessibilityDelegate.sendAccessibilityEventUnchecked(this, event); } else { sendAccessibilityEventUncheckedInternal(event); }}public void sendAccessibilityEventUnchecked(View host, AccessibilityEvent event) { host.sendAccessibilityEventUncheckedInternal(event);}public void sendAccessibilityEventUncheckedInternal(AccessibilityEvent event) { if (!isShown()) { return; } ... // 此處交由TextView所在父View進行處理，為責(zé)任鏈模式，事件經(jīng)過層層向上傳遞，最終交由ViewRootImpl進行處理 ViewParent parent = getParent(); if (parent != null) { getParent().requestSendAccessibilityEvent(this, event); }}

@Overridepublic boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event) { ... // 本地調(diào)用到AccessibilityManager進行事件發(fā)送 mAccessibilityManager.sendAccessibilityEvent(event); return true;}

public void sendAccessibilityEvent(AccessibilityEvent event) { final IAccessibilityManager service; final int userId; synchronized (mLock) { // 獲取system_server的Accessibility實名服務(wù) service = getServiceLocked(); ... }  try { ... long identityToken = Binder.clearCallingIdentity(); // binder call 到服務(wù)端，進行事件分發(fā)中轉(zhuǎn) doRecycle = service.sendAccessibilityEvent(event, userId); Binder.restoreCallingIdentity(identityToken); ... } catch (RemoteException re) { Log.e(LOG_TAG, "Error during sending " + event + " ", re); } finally { ... }}

// binder call 到服務(wù)端，觸發(fā)事件派發(fā)@Overridepublic boolean sendAccessibilityEvent(AccessibilityEvent event, int userId) { synchronized (mLock) { ... if (mSecurityPolicy.canDispatchAccessibilityEventLocked(event)) {  ...  notifyAccessibilityServicesDelayedLocked(event, false);  notifyAccessibilityServicesDelayedLocked(event, true); } ... } return (OWN_PROCESS_ID != Binder.getCallingPid());}private void notifyAccessibilityServicesDelayedLocked(AccessibilityEvent event, boolean isDefault) { try { UserState state = getCurrentUserStateLocked(); for (int i = 0, count = state.mBoundServices.size(); i < count; i++) {  Service service = state.mBoundServices.get(i);  if (service.mIsDefault == isDefault) {  if (canDispatchEventToServiceLocked(service, event)) {   // 調(diào)用內(nèi)部服務(wù)，以觸發(fā)事件派發(fā)   service.notifyAccessibilityEvent(event);  }  } } } catch (IndexOutOfBoundsException oobe) { ... }}class Service extends IAccessibilityServiceConnection.Stub implements ServiceConnection, DeathRecipient { public void notifyAccessibilityEvent(AccessibilityEvent event) { synchronized (mLock) {  ...  if ((mNotificationTimeout > 0)   && (eventType != AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED)) {  ...  // 按照慣例，異步分發(fā)到客戶端進行派發(fā)  message = mEventDispatchHandler.obtainMessage(eventType);  } else {  message = mEventDispatchHandler.obtainMessage(eventType, newEvent);  }  mEventDispatchHandler.sendMessageDelayed(message, mNotificationTimeout); } } }public Handler mEventDispatchHandler = new Handler(mMainHandler.getLooper()) { @Override public void handleMessage(Message message) { final int eventType = message.what; AccessibilityEvent event = (AccessibilityEvent) message.obj; notifyAccessibilityEventInternal(eventType, event); }};private void notifyAccessibilityEventInternal(int eventType, AccessibilityEvent event) { IAccessibilityServiceClient listener; ... // mServiceInterface是通過bind客戶端的AccessibilityService，在onServiceConnected連接成功后，獲取到binder proxy轉(zhuǎn)化來的，以這種方式實現(xiàn)了system_server與客戶端的通信 listener = mServiceInterface; ... try { listener.onAccessibilityEvent(event); if (DEBUG) {  Slog.i(LOG_TAG, "Event " + event + " sent to " + listener); } } catch (RemoteException re) { Slog.e(LOG_TAG, "Error during sending " + event + " to " + listener, re); } finally { event.recycle(); }}

// 抽象方法，模板模式，被系統(tǒng)主動調(diào)用public abstract void onAccessibilityEvent(AccessibilityEvent event);// 該service是被system_server主動綁定的，獲取到IAccessibilityServiceClientWrapper的proxy來實現(xiàn)系統(tǒng)的主動調(diào)用@Overridepublic final IBinder onBind(Intent intent) { return new IAccessibilityServiceClientWrapper(this, getMainLooper(), new Callbacks() { ... @Override public void onAccessibilityEvent(AccessibilityEvent event) {  AccessibilityService.this.onAccessibilityEvent(event); } ... }}// 收到binder調(diào)用后，使用handler異步進行事件的處理public void onAccessibilityEvent(AccessibilityEvent event) { Message message = mCaller.obtainMessageO(DO_ON_ACCESSIBILITY_EVENT, event); mCaller.sendMessage(message);}@Overridepublic void executeMessage(Message message) { switch (message.what) { case DO_ON_ACCESSIBILITY_EVENT: {  AccessibilityEvent event = (AccessibilityEvent) message.obj;  if (event != null) {  AccessibilityInteractionClient.getInstance().onAccessibilityEvent(event);  // 通過回調(diào)調(diào)用以觸發(fā)事件  mCallback.onAccessibilityEvent(event);  ...  } } return; }}

public AccessibilityNodeInfo getRootInActiveWindow() { // 查找父節(jié)點的操作沒有在自己的類中實現(xiàn)，而是交由了同一進程的Client管理類進行處理 return AccessibilityInteractionClient.getInstance().getRootInActiveWindow(mConnectionId);}

public AccessibilityNodeInfo getRootInActiveWindow(int connectionId) { return findAccessibilityNodeInfoByAccessibilityId(connectionId,  AccessibilityNodeInfo.ACTIVE_WINDOW_ID, AccessibilityNodeInfo.ROOT_NODE_ID,  false, AccessibilityNodeInfo.FLAG_PREFETCH_DESCENDANTS);}public AccessibilityNodeInfo findAccessibilityNodeInfoByAccessibilityId(int connectionId,  int accessibilityWindowId, long accessibilityNodeId, boolean bypassCache,  int prefetchFlags) { ... // 嘗試binder call到system_server，請求中轉(zhuǎn)到其它APP進程中查詢父節(jié)點信息，注意的是這里AccessibilityInteractionClient本身是個binder服務(wù)端，把this傳到system_server后，其它進程可以通過這個引用拿到binder proxy，以實現(xiàn)通信 final boolean success = connection.findAccessibilityNodeInfoByAccessibilityId(   accessibilityWindowId, accessibilityNodeId, interactionId, this,   prefetchFlags, Thread.currentThread().getId()); Binder.restoreCallingIdentity(identityToken); // If the scale is zero the call has failed. if (success) { // 調(diào)用成功后，這里會嘗試同步獲取結(jié)果 List<AccessibilityNodeInfo> infos = getFindAccessibilityNodeInfosResultAndClear(  interactionId); finalizeAndCacheAccessibilityNodeInfos(infos, connectionId); if (infos != null && !infos.isEmpty()) {  return infos.get(0); } }  ... }

@Overridepublic boolean findAccessibilityNodeInfoByAccessibilityId( int accessibilityWindowId, long accessibilityNodeId, int interactionId, IAccessibilityInteractionConnectionCallback callback, int flags, long interrogatingTid) throws RemoteException { ... // 獲取到其他APP的節(jié)點獲取服務(wù) IAccessibilityInteractionConnection connection = null; ... resolvedWindowId = resolveAccessibilityWindowIdLocked(accessibilityWindowId); ... if (!permissionGranted) { return false; } else { connection = getConnectionLocked(resolvedWindowId); if (connection == null) {  return false; } } ... // 這里的callback為之前應(yīng)用的服務(wù)proxy句柄，將它傳入是為了之后的信息通信不再需要經(jīng)過system_server中轉(zhuǎn)，而是直接可以APP對APP的進行通信 connection.findAccessibilityNodeInfoByAccessibilityId(accessibilityNodeId,  partialInteractiveRegion, interactionId, callback, mFetchFlags | flags,  interrogatingPid, interrogatingTid, spec); ...}

@Overridepublic void findAccessibilityNodeInfoByAccessibilityId(long accessibilityNodeId, Region interactiveRegion, int interactionId, IAccessibilityInteractionConnectionCallback callback, int flags, int interrogatingPid, long interrogatingTid, MagnificationSpec spec) { ViewRootImpl viewRootImpl = mViewRootImpl.get(); if (viewRootImpl != null && viewRootImpl.mView != null) { // 這里也只是委托給控制類進行細(xì)節(jié)操作的處理 viewRootImpl.getAccessibilityInteractionController()  .findAccessibilityNodeInfoByAccessibilityIdClientThread(accessibilityNodeId,   interactiveRegion, interactionId, callback, flags, interrogatingPid,   interrogatingTid, spec); } else { ... }}

private void findAccessibilityNodeInfoByAccessibilityIdUiThread(Message message) { ... // 初始化將會返回的節(jié)點 List<AccessibilityNodeInfo> infos = mTempAccessibilityNodeInfoList; infos.clear(); try { if (mViewRootImpl.mView == null || mViewRootImpl.mAttachInfo == null) {  return; } mViewRootImpl.mAttachInfo.mAccessibilityFetchFlags = flags; View root = null; if (accessibilityViewId == AccessibilityNodeInfo.UNDEFINED_ITEM_ID) {  root = mViewRootImpl.mView; } else {  root = findViewByAccessibilityId(accessibilityViewId); } ... } finally { try {  ...  adjustIsVisibleToUserIfNeeded(infos, interactiveRegion);  // 通過callback binder proxy句柄，將節(jié)點信息binder回應(yīng)用  callback.setFindAccessibilityNodeInfosResult(infos, interactionId);  infos.clear(); } catch (RemoteException re) {  /* ignore - the other side will time out */ } ... }}

public void setFindAccessibilityNodeInfosResult(List<AccessibilityNodeInfo> infos,  int interactionId) { synchronized (mInstanceLock) { if (interactionId > mInteractionId) {  if (infos != null) {  ...  // 設(shè)置應(yīng)用的返回節(jié)點信息  if (!isIpcCall) {   mFindAccessibilityNodeInfosResult = new ArrayList<>(infos);  } else {   mFindAccessibilityNodeInfosResult = infos;  }  } else {  mFindAccessibilityNodeInfosResult = Collections.emptyList();  }  mInteractionId = interactionId; } // 釋放鎖，停止等待，節(jié)點信息已經(jīng)取回 mInstanceLock.notifyAll(); }}

public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(String text) { ... // 一樣的流程，通過AccessibilityInteractionClient去獲取信息 AccessibilityInteractionClient client = AccessibilityInteractionClient.getInstance(); return client.findAccessibilityNodeInfosByText(mConnectionId, mWindowId, mSourceNodeId,  text);}``` 

```javaprivate void performAccessibilityActionUiThread(Message message) { View target = null; if (accessibilityViewId != AccessibilityNodeInfo.UNDEFINED_ITEM_ID) { target = findViewByAccessibilityId(accessibilityViewId); } else { target = mViewRootImpl.mView; } if (target != null && isShown(target)) { AccessibilityNodeProvider provider = target.getAccessibilityNodeProvider(); if (provider != null) {  if (virtualDescendantId != AccessibilityNodeInfo.UNDEFINED_ITEM_ID) {  // 在客戶端執(zhí)行performAction操作  succeeded = provider.performAction(virtualDescendantId, action,   arguments);  } else {  succeeded = provider.performAction(AccessibilityNodeProvider.HOST_VIEW_ID,   action, arguments);  } } else if (virtualDescendantId == AccessibilityNodeInfo.UNDEFINED_ITEM_ID) {  succeeded = target.performAccessibilityAction(action, arguments); } }}

public boolean performAccessibilityActionInternal(int action, Bundle arguments) { ... switch (action) { case AccessibilityNodeInfo.ACTION_CLICK: {  if (isClickable()) {  // 最終調(diào)用到我們熟悉的View.performClick方法  performClick();  return true;  } } break; ...}