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這篇文章主要介紹“Android無障礙服務performAction怎么調用”，在日常操作中，相信很多人在Android無障礙服務performAction怎么調用問題上存在疑惑，小編查閱了各式資料，整理出簡單好用的操作方法，希望對大家解答”Android無障礙服務performAction怎么調用”的疑惑有所幫助！接下來，請跟著小編一起來學習吧！
無障礙服務可以模擬一些用戶操作，無障礙可以處理的對象，通過類 AccessibilityNodeInfo 表示，通過無障礙服務，可以通過它的 performAction 方法來觸發一些 action ，包括：
ACTION_FOCUS // 獲取焦點 ACTION_CLEAR_FOCUS // 清除焦點 ACTION_SELECT // 選中 ACTION_CLEAR_SELECTION // 清除選中狀態 ACTION_ACCESSIBILITY_FOCUS // 無障礙焦點 ACTION_CLEAR_ACCESSIBILITY_FOCUS // 清除無障礙焦點 ACTION_CLICK // 點擊 ACTION_LONG_CLICK // 長按 ACTION_NEXT_AT_MOVEMENT_GRANULARITY // 下一步移動 ACTION_PREVIOUS_AT_MOVEMENT_GRANULARITY // 上一步移動 ACTION_NEXT_HTML_ELEMENT // 下一個 html 元素 ACTION_PREVIOUS_HTML_ELEMENT // 上一個 html 元素 ACTION_SCROLL_FORWARD // 向前滑動 ACTION_SCROLL_BACKWARD // 向后滑動
他們都可以通過performAction方法進行處理：
// in AccessibilityNodeInfo
public boolean performAction(int action) {
enforceSealed();
if (!canPerformRequestOverConnection(mConnectionId, mWindowId, mSourceNodeId)) {
return false;
}
AccessibilityInteractionClient client = AccessibilityInteractionClient.getInstance();
return client.performAccessibilityAction(mConnectionId, mWindowId, mSourceNodeId,
action, null);
}在這個方法中，第一步是檢查 perform 是否可以通過 connection 請求，這里 connection 檢查是根據通過 binder 通信傳遞過來的 id 檢查連接是否正常。 然后通過AccessibilityInteractionClient對象，調用它的performAccessibilityAction方法去進行實際操作的。
這個類是一個執行可訪問性交互的單例，它可以根據 View 的快照查詢遠程的 View 層次結構，以及通過 View 層次結構，來請求對 View 執行某項操作。
基本原理：內容檢索 API 從客戶端的角度來看是同步的，但在內部它們是異步的。客戶端線程調用系統請求操作并提供回調以接收結果，然后等待該結果的超時。系統強制執行安全性并將請求委托給給定的視圖層次結構， 在該視圖層次結構中發布消息（來自 Binder 線程），描述 UI 線程要執行的內容，其結果是通過上述回調傳遞的。但是，被阻塞的客戶端線程和目標視圖層次結構的主 UI 線程可以是同一個線程，例如無障礙服務和 Activity 在同一個進程中運行，因此它們在同一個主線程上執行。 在這種情況下，檢索將會失敗，因為 UI 線程在等待檢索結果，會導致阻塞。 為了避免在進行調用時出現這種情況，客戶端還會傳遞其進程和線程 ID，以便訪問的視圖層次結構可以檢測發出請求的客戶端是否正在其主 UI 線程中運行。 在這種情況下，視圖層次結構，特別是對它執行 IPC 的綁定線程，不會發布要在 UI 線程上運行的消息，而是將其傳遞給單例交互客戶端，通過該客戶端發生所有交互，后者負責執行開始等待通過回調傳遞的異步結果之前的消息。在這種情況下，已經收到預期的結果，因此不執行等待。
上面是官方備注的描述，大概意思最好不要在主線程執行檢索操作。
繼續跟進它的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;
}這里通過 getConnection(connectionId) 獲取了一個 IAccessibilityServiceConnection 。
public static IAccessibilityServiceConnection getConnection(int connectionId) {
synchronized (sConnectionCache) {
return sConnectionCache.get(connectionId);
}
}這里的 sConnectionCache 通過 AccessibilityInteractionClient 的addConnection添加數據的，addConnection在 AccessbilityService 創建初始化時調用的：
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;
}也就是說，在 AccessbilityService 創建時，會將一個表示連接的對象存到 AccessibilityInteractionClient 的連接緩存中。
它是 AccessibilityManagerService 向 AccessbilityService 暴露的 AIDL 接口，提供給 AccessbilityService 調用AccessibilityManagerService 的能力。 上面的 performAction 流程中，調用到了 connection 的performAccessibilityAction方法。 而 IAccessibilityServiceConnection 有兩個實現類，AccessibilityServiceConnectionImpl和AbstractAccessibilityServiceConnection，前者都是空實現，顯然不是我們要調用到的地方，后者的performAccessibilityAction：
@Override
public 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);
}最后的一行調用：
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;
// 同步獲取 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();
}
}
// 通過 connection 調用到遠程服務的performAccessibilityAction
final int interrogatingPid = Binder.getCallingPid();
final long identityToken = Binder.clearCallingIdentity();
try {
// 無論操作是否成功，它都是由用戶操作的無障礙服務生成的，因此請注意用戶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;
}在這個方法中，通過 connection 調用到了遠端的 performAccessibilityAction 方法。
關鍵的一行是：
connection.getRemote().performAccessibilityAction(accessibilityNodeId, action, arguments, interactionId, callback, fetchFlags, interrogatingPid, interrogatingTid);
這里的 connection 類型定義成了RemoteAccessibilityConnection。
RemoteAccessibilityConnection 是AccessibilityWindowManager的內部類，它的getRemote()返回類型是IAccessibilityInteractionConnection。
此類為 AccessibilityManagerService 提供 API 來管理 AccessibilityWindowInfo 和 WindowInfos。
這是一個 AIDL 中定義的接口，用來進行 給定 window 中 AccessibilityManagerService 和 ViewRoot 之間交互的接口。
也就是說getRemote(). performAccessibilityAction(...)最終來到了 ViewRootImpl 中。
ViewRootImpl 中存在一個內部類AccessibilityInteractionConnection，它是這個 ViewAncestor 提供給 AccessibilityManagerService 的一個接口，后者可以與這個 ViewAncestor 中的視圖層次結構進行交互。
它的performAccessibilityAction實現是：
@Override
public 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) {
/* best effort - ignore */
}
}
}內部又是通過代理調用 ，ViewRootImpl 的 getAccessibilityInteractionController() 返回了一個 AccessibilityInteractionController 對象。
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);
}組裝了一個 message ，并通過 scheduleMessage 方法去執行：
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);
}
}
}
}這里實際上，如果是在主線程，則處理消息，如果不是，則發送消息到主線程處理。handler 的類型是 PrivateHandler ，在 AccessibilityInteractionController 內部定義。
它的處理消息方法的實現是：
@Override
public 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);
}
}執行到了 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) {
// 單獨處理這個 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) {
/* ignore - the other side will time out */
}
}
}在這個流程中，分為三種情況去真正執行 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
當能夠通過 View 獲取到 AccessibilityNodeProvider 對象是，通過它的 performAction 方法，去執行真正的調用，它的真正調用在 AccessibilityNodeProviderCompat中，這個 Compat 的實現在ExploreByTouchHelper中的內部類MyNodeProvider中：
@Override
public boolean performAction(int virtualViewId, int action, Bundle arguments) {
return ExploreByTouchHelper.this.performAction(virtualViewId, action, arguments);
}在 ExploreByTouchHelper 中繼續查看：
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);
}
}前者調用到了 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的實現是：
public boolean performAccessibilityAction(View host, int action, Bundle args) {
return host.performAccessibilityActionInternal(action, args);
}也是調用到了 View 的performAccessibilityActionInternal 。 performAccessibilityActionInternal 的實現是：
// in View.java
public 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 為例，內部調用是：
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();
}這樣就調用到了 View 的點擊事件。
3. View. AccessibilityNodeProvider == null && virtualDescendantId == AccessibilityNodeProvider.HOST_VIEW_ID
target.performAccessibilityAction(action, arguments);
這里 target 是個 View， 也是走的 View 的 performAccessibilityAction ，和上面流程一樣。
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。
到此，關于“Android無障礙服務performAction怎么調用”的學習就結束了，希望能夠解決大家的疑惑。理論與實踐的搭配能更好的幫助大家學習，快去試試吧！若想繼續學習更多相關知識，請繼續關注億速云網站，小編會繼續努力為大家帶來更多實用的文章！
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