簡介
創(chuàng)新互聯(lián)建站是專業(yè)的膠州網(wǎng)站建設(shè)公司，膠州接單;提供成都網(wǎng)站設(shè)計(jì)、網(wǎng)站制作,網(wǎng)頁設(shè)計(jì),網(wǎng)站設(shè)計(jì),建網(wǎng)站,PHP網(wǎng)站建設(shè)等專業(yè)做網(wǎng)站服務(wù);采用PHP框架,可快速的進(jìn)行膠州網(wǎng)站開發(fā)網(wǎng)頁制作和功能擴(kuò)展;專業(yè)做搜索引擎喜愛的網(wǎng)站,專業(yè)的做網(wǎng)站團(tuán)隊(duì),希望更多企業(yè)前來合作!
AccessibilityService的設(shè)計(jì)初衷是為了輔助有身體缺陷的群體使用Android應(yīng)用，它的設(shè)計(jì)貫穿著Android的控件樹View, ViewGroup, ViewRootImpl體系。借助于system_server進(jìn)程的中轉(zhuǎn)，能夠注冊Accessibility事件的客戶端可以具備通過system_server提供的Accessibility服務(wù)來實(shí)現(xiàn)監(jiān)聽、操作其它應(yīng)用視圖的功能。這個(gè)功能十分強(qiáng)大，可以模擬用戶的行為去操作其它APP，常常被用在自動(dòng)化測試、微信搶紅包、自動(dòng)回復(fù)等功能實(shí)現(xiàn)中。
寫這個(gè)的初衷有二：
整體圖
類圖
整體設(shè)計(jì)圖
實(shí)例代碼
重慶分公司
重慶分公司
public class AutoDismissService extends AccessibilityService {
@Override
public void onAccessibilityEvent(AccessibilityEvent event) {
if (event == null) {
return;
}
// 自動(dòng)將android系統(tǒng)彈出的其它c(diǎn)rash dialog取消
dismissAppErrorDialogIfExists(event);
}
private void dismissAppErrorDialogIfExists(AccessibilityEvent event) {
// WINDOW視圖變化才進(jìn)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(diǎn)擊Node
AccessibilityNodeInfo nodeInfo = findViewByText("OK", true);
if (nodeInfo != null) {
// 查找到后執(zhí)行點(diǎn)擊操作
performViewClick(nodeInfo);
}
}
public AccessibilityNodeInfo findViewByText(String text, boolean clickable) {
// 獲取當(dāng)前窗口父節(jié)點(diǎn)
AccessibilityNodeInfo accessibilityNodeInfo = getRootInActiveWindow();
if (accessibilityNodeInfo == null) {
return null;
}
// 獲取到滿足字符要求的節(jié)點(diǎn)
List 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(jìn)行查詢，直到尋找到可點(diǎn)擊的節(jié)點(diǎn)
while (nodeInfo != null) {
if (nodeInfo.isClickable()) {
nodeInfo.performAction(AccessibilityNodeInfo.ACTION_CLICK);
break;
}
nodeInfo = nodeInfo.getParent();
}
}
} 以上是一個(gè)典型的實(shí)現(xiàn)Accessibility功能的JAVA代碼，主要涉及三點(diǎn)功能：
本篇文章將會(huì)圍繞著這三點(diǎn)主要功能進(jìn)行源碼分析
源碼分析
常見 AccessibilityEvent 事件種類
| 序號(hào) | 種類名稱 | 觸發(fā)時(shí)機(jī) |
|---|---|---|
| 1 | TYPE_VIEW_CLICKED | 可點(diǎn)擊的組件被點(diǎn)擊 |
| 2 | TYPE_VIEW_LONG_CLICKED | 可點(diǎn)擊的組件被長按 |
| 3 | TYPE_VIEW_SELECTED | 組件被選中 |
| 4 | TYPE_VIEW_FOCUSED | 組件獲取到了焦點(diǎn) |
| 5 | TYPE_VIEW_TEXT_CHANGED | 組件中的文本發(fā)生變化 |
| 6 | TYPE_VIEW_SCROLLED | 組件被滑動(dòng) |
| 7 | TYPE_WINDOW_STATE_CHANGED | dialog等被打開 |
| 8 | TYPE_NOTIFICATION_STATE_CHANGED | 通知彈出 |
| 9 | TYPE_WINDOW_CONTENT_CHANGED | 組件樹發(fā)生了變化 |
onAccessibilityEvent 觸發(fā)流程
這里以TextView.setText觸發(fā)事件變化流程為例進(jìn)行分析
TextView.setText
應(yīng)用組件狀態(tài)發(fā)生變化
frameworks/base/core/java/android/widget/TextView.java
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(gè)Runnable，意味著這里的流程會(huì)進(jìn)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(jìn)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(jìn)行處理
ViewParent parent = getParent();
if (parent != null) {
getParent().requestSendAccessibilityEvent(this, event);
}
}ViewRootImpl.requestSendAccessibilityEvent
ViewRootImpl將事件派發(fā)到system_server
frameworks/base/core/java/android/view/ViewRootImpl.java
@Override
public boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event) {
...
// 本地調(diào)用到AccessibilityManager進(jìn)行事件發(fā)送
mAccessibilityManager.sendAccessibilityEvent(event);
return true;
}frameworks/base/core/java/android/view/accessibility/AccessibilityManager.java
public void sendAccessibilityEvent(AccessibilityEvent event) {
final IAccessibilityManager service;
final int userId;
synchronized (mLock) {
// 獲取system_server的Accessibility實(shí)名服務(wù)
service = getServiceLocked();
...
}
try {
...
long identityToken = Binder.clearCallingIdentity();
// binder call 到服務(wù)端，進(jìn)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 {
...
}
}AccessibilityManagerService.sendAccessibilityEvent
system_server將事件分發(fā)到各個(gè)監(jiān)聽組件變化的Service
frameworks/base/services/accessibility/java/com/android/server/accessibility/AccessibilityManagerService.java
// binder call 到服務(wù)端，觸發(fā)事件派發(fā)
@Override
public 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(jìn)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(shí)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();
}
}AccessibilityService.onAccessibilityEvent
APP接收到組件變化的事件，并可以選擇做出相應(yīng)的處理
frameworks/base/core/java/android/accessibilityservice/AccessibilityService.java
// 抽象方法，模板模式，被系統(tǒng)主動(dòng)調(diào)用
public abstract void onAccessibilityEvent(AccessibilityEvent event);
// 該service是被system_server主動(dòng)綁定的，獲取到IAccessibilityServiceClientWrapper的proxy來實(shí)現(xiàn)系統(tǒng)的主動(dòng)調(diào)用
@Override
public 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(jìn)行事件的處理
public void onAccessibilityEvent(AccessibilityEvent event) {
Message message = mCaller.obtainMessageO(DO_ON_ACCESSIBILITY_EVENT, event);
mCaller.sendMessage(message);
}
@Override
public 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;
}
}getRootInActiveWindow 父節(jié)點(diǎn)獲取流程
在調(diào)用findAccessibilityNodeInfosByText之前，需要通過getRootInActiveWindow方法獲取到父節(jié)點(diǎn)，才能通過調(diào)用父AccessibilityNodeInfo的方法進(jìn)行其子節(jié)點(diǎn)信息查詢
AccessibilityService.getRootInActiveWindow
frameworks/base/core/java/android/accessibilityservice/AccessibilityService.java
public AccessibilityNodeInfo getRootInActiveWindow() {
// 查找父節(jié)點(diǎn)的操作沒有在自己的類中實(shí)現(xiàn)，而是交由了同一進(jìn)程的Client管理類進(jìn)行處理
return AccessibilityInteractionClient.getInstance().getRootInActiveWindow(mConnectionId);
}frameworks/base/core/java/android/view/accessibility/AccessibilityInteractionClient.java
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(jìn)程中查詢父節(jié)點(diǎn)信息，注意的是這里AccessibilityInteractionClient本身是個(gè)binder服務(wù)端，把this傳到system_server后，其它進(jìn)程可以通過這個(gè)引用拿到binder proxy，以實(shí)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(huì)嘗試同步獲取結(jié)果
List infos = getFindAccessibilityNodeInfosResultAndClear(
interactionId);
finalizeAndCacheAccessibilityNodeInfos(infos, connectionId);
if (infos != null && !infos.isEmpty()) {
return infos.get(0);
}
}
...
} Service.findAccessibilityNodeInfoByAccessibilityId
注意一下，這里的Service不是Android中的四大組件的Service，取名叫AccessiblitManagerServiceInternal其實(shí)更合適
frameworks/base/services/accessibility/java/com/android/server/accessibility/AccessibilityManagerService.java
@Override
public 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(diǎn)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(jìn)行通信
connection.findAccessibilityNodeInfoByAccessibilityId(accessibilityNodeId,
partialInteractiveRegion, interactionId, callback, mFetchFlags | flags,
interrogatingPid, interrogatingTid, spec);
...
}AccessibilityInteractionConnection.findAccessibilityNodeInfoByAccessibilityId
這里調(diào)用到了APP端，其實(shí)同onAccessibilityEvent調(diào)用流程一樣，是APP->SYSTEM->APP的調(diào)用順序
frameworks/base/core/java/android/view/ViewRootImpl.java
@Override
public 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(jìn)行細(xì)節(jié)操作的處理
viewRootImpl.getAccessibilityInteractionController()
.findAccessibilityNodeInfoByAccessibilityIdClientThread(accessibilityNodeId,
interactiveRegion, interactionId, callback, flags, interrogatingPid,
interrogatingTid, spec);
} else {
...
}
}frameworks/base/core/java/android/view/AccessibilityInteractionController.java
private void findAccessibilityNodeInfoByAccessibilityIdUiThread(Message message) {
...
// 初始化將會(huì)返回的節(jié)點(diǎn)
List 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(diǎn)信息binder回應(yīng)用
callback.setFindAccessibilityNodeInfosResult(infos, interactionId);
infos.clear();
} catch (RemoteException re) {
/* ignore - the other side will time out */
}
...
}
} AccessibilityInteractionClient.setFindAccessibilityNodeInfosResult
frameworks/base/core/java/android/view/accessibility/AccessibilityInteractionClient.java
public void setFindAccessibilityNodeInfosResult(Listinfos, int interactionId) { synchronized (mInstanceLock) { if (interactionId > mInteractionId) { if (infos != null) { ... // 設(shè)置應(yīng)用的返回節(jié)點(diǎn)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(diǎn)信息已經(jīng)取回 mInstanceLock.notifyAll(); } }
findAccessibilityNodeInfosByText與performAction 對目標(biāo)節(jié)點(diǎn)進(jìn)行操作
AccessibilityNodeInfo.findAccessibilityNodeInfosByText
找到父節(jié)點(diǎn)信息后，就可以通過父節(jié)點(diǎn)獲取對應(yīng)的子節(jié)點(diǎn)信息了
frameworks/base/core/java/android/view/accessibility/AccessibilityNodeInfo.java
public ListfindAccessibilityNodeInfosByText(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); } ```
以下的代碼流程同getRootInActiveWindow大概一致，就不詳細(xì)分析了
#### AccessibilityNodeInfo.performAction
獲取到對應(yīng)子節(jié)點(diǎn)后，通過performAction可以執(zhí)行對應(yīng)的操作了，如常用的點(diǎn)擊
最終回調(diào)用到AccessibilityInteractionController,獲取到AccessibilityProvier后就可以執(zhí)行performAction的最終操作了
frameworks/base/core/java/android/view/AccessibilityInteractionController.java
```java
private 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);
}
}
}frameworks/base/core/java/android/view/View.java
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;
...
}分析到這里可以看到，Accessibility服務(wù)框架類似于hook在Android View組件樹中的一套實(shí)現(xiàn)，它并不是獨(dú)立的一套機(jī)制，而是”寄生”在View的顯示、事件分發(fā)的流程中。
總結(jié)
功能實(shí)現(xiàn)依賴于ViewRootImpl, ViewGroup, View視圖層級(jí)管理的基本架構(gòu)。在視圖變化時(shí)發(fā)出事件、當(dāng)收到視圖操作請求時(shí)也能夠作出響應(yīng)。
system_server在實(shí)現(xiàn)該功能的過程中扮演著中間人的角色。當(dāng)被監(jiān)聽APP視圖變化時(shí)，APP首先會(huì)發(fā)出事件到system_server，隨后再中轉(zhuǎn)到監(jiān)聽者APP端。當(dāng)監(jiān)聽者APP想要執(zhí)行視圖操作時(shí)，也是首先在system_server中找到對應(yīng)的客戶端binder proxy，再調(diào)用相應(yīng)接口調(diào)用到被監(jiān)聽APP中。完成相關(guān)操作后，通過已經(jīng)獲取到的監(jiān)聽APP binder proxy句柄，直接binder call到對應(yīng)的監(jiān)聽客戶端。
無障礙權(quán)限十分重要，切記不可濫用，APP自身也需要有足夠的安全意識(shí)，防止惡意應(yīng)用通過該服務(wù)獲取用戶隱私信息
好了，以上就是這篇文章的全部內(nèi)容了，希望本文的內(nèi)容對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，如果有疑問大家可以留言交流，謝謝大家對創(chuàng)新互聯(lián)的支持。
