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Android開發input問題解決分析_Android

作者:咖啡你沖不沖 ? 更新時間: 2022-12-22 編程語言

Android Input

Android Input指的是輸入事件,主要是觸摸滑動,當然還包括類似藍牙外設的輸入。Input涉及到的主要模塊

  • EventHub :對輸入事件進行映射
  • InputReader : 收集input事件
  • InputDispatcher : 將事件分發到上層
  • InputManager : framework中對input事件的接收和分發
  • WMS : 管理窗口,收集和分發input事件

本篇主要以framework的視角來debug input問題,介紹input的資料已經很多了,所以不講input傳遞流程和機制,只看如何去解決問題。

從framework的視角,首先我們要排查input driver的問題,比如從屏幕觸摸輸入的,那就是顯示屏的input驅動;如果是藍牙外設輸入的,那就需要找BT的驅動層。

adb shell getEvent

然后再輸入,看鍵值是否正常,如果getEvent都沒有收到,就不屬于framework的范疇了。

確定驅動沒有問題之后,就可以通過動態或靜態開啟debug log。不同廠商的開關log的命令有些差異,打印log的內容也不太一樣。

這里我們直接以本地debug為例,參考Android T版本的common code自己添加關鍵log,然后開始復現問題,檢查問題時間點的log。順便補充一下,可以通過如下命令使時間顯示到秒,這樣方便復現問題時對應log時間

adb shell settings put secure clock_seconds 1

Step1.查看ViewRootImpl是否有收到input event

/frameworks/base/core/java/android/view/ViewRootImpl.java

      @UnsupportedAppUsage
      void enqueueInputEvent(InputEvent event,
              InputEventReceiver receiver, int flags, boolean processImmediately) {
          QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);
          if (event instanceof MotionEvent) {
              MotionEvent me = (MotionEvent) event;
              if (me.getAction() == MotionEvent.ACTION_CANCEL) {
                  EventLog.writeEvent(EventLogTags.VIEW_ENQUEUE_INPUT_EVENT, "Motion - Cancel",
                          getTitle().toString());
              }
          } else if (event instanceof KeyEvent) {
              KeyEvent ke = (KeyEvent) event;
              if (ke.isCanceled()) {
                  EventLog.writeEvent(EventLogTags.VIEW_ENQUEUE_INPUT_EVENT, "Key - Cancel",
                          getTitle().toString());
              }
          }
          // Always enqueue the input event in order, regardless of its time stamp.
          // We do this because the application or the IME may inject key events
          // in response to touch events and we want to ensure that the injected keys
          // are processed in the order they were received and we cannot trust that
          // the time stamp of injected events are monotonic.
          QueuedInputEvent last = mPendingInputEventTail;
          if (last == null) {
              mPendingInputEventHead = q;
              mPendingInputEventTail = q;
          } else {
              last.mNext = q;
              mPendingInputEventTail = q;
          }
          mPendingInputEventCount += 1;
          Trace.traceCounter(Trace.TRACE_TAG_INPUT, mPendingInputEventQueueLengthCounterName,
                  mPendingInputEventCount);
          //添加log打印關鍵信息
          Log.i(">_<!!","enqueueInputEvent: event = " + event + " ,this = " + this);
          if (processImmediately) {
              doProcessInputEvents();
          } else {
              scheduleProcessInputEvents();
          }
      }

這里只需要根據添加的log查看兩個參數即可,event會打印出來 KeyEvent的action和keyCode,我們需要看下這里的action和keyCode是否有紊亂的情況,如果輸入和get到的不對應,那還是需要driver來協調。后面打印出來的this就是此ViewRootImpl對象,具體內容可以看它的toString方法。

我們只需要在最終的log中觀察這句是否打印出來,如果打印出來了,說明input事件已經成功發送到應用端了,跳過下面步驟,直接檢查Step5,如果沒打印這段log,再看Step2

Step2. 查看inputDispatcher是否有收到input event

/frameworks/native/services/inputflinger/dispatcher/InputDispatcher.cpp

  bool InputDispatcher::dispatchKeyLocked(nsecs_t currentTime, std::shared_ptr<KeyEntry> entry,
                                          DropReason* dropReason, nsecs_t* nextWakeupTime) {
      // Preprocessing.
      if (!entry->dispatchInProgress) {
          // 這個是AOSP的log機制,不用再另外添加log
          logOutboundKeyDetails("dispatchKey - ", *entry);
      }
  void InputDispatcher::logOutboundKeyDetails(const char* prefix, const KeyEntry& entry) {
      //if (DEBUG_OUTBOUND_EVENT_DETAILS) {
        if (true) {
          ALOGD("%seventTime=%" PRId64 ", deviceId=%d, source=0x%x, displayId=%" PRId32 ", "
                "policyFlags=0x%x, action=0x%x, flags=0x%x, keyCode=0x%x, scanCode=0x%x, "
                "metaState=0x%x, repeatCount=%d, downTime=%" PRId64,
                prefix, entry.eventTime, entry.deviceId, entry.source, entry.displayId,
                entry.policyFlags, entry.action, entry.flags, entry.keyCode, entry.scanCode,
                entry.metaState, entry.repeatCount, entry.downTime);
      }
  }

這里AOSP的log已經添加的很全面了,我們只需要手動將打印條件置為true即可。這段log中同樣可以對應上action和keyCode,不過c++代碼打印出來的是十六進制,但是也和上面java code中打印出來的字符串是一一對應的。如果我們最終可以搜索到這段log,說明inputDispatcher已經收到input event了,那么直接快進到Step4檢查inputDispatcher狀態是否正常。如果沒有查看到這句log,再看Step3

Step3. 查看inputreader線程里面是否有keycode

/frameworks/native/services/inputflinger/reader/mapper/KeyboardInputMapper.cpp

                                       int32_t usageCode) {
      int32_t keyCode;
      int32_t keyMetaState;
      uint32_t policyFlags;
      if (getDeviceContext().mapKey(scanCode, usageCode, mMetaState, &keyCode, &keyMetaState,
                                    &policyFlags)) {
          keyCode = AKEYCODE_UNKNOWN;
          keyMetaState = mMetaState;
          policyFlags = 0;
      }
      if (mParameters.handlesKeyRepeat) {
          policyFlags |= POLICY_FLAG_DISABLE_KEY_REPEAT;
      }
      NotifyKeyArgs args(getContext()->getNextId(), when, readTime, getDeviceId(), mSource,
                         getDisplayId(), policyFlags,
                         down ? AKEY_EVENT_ACTION_DOWN : AKEY_EVENT_ACTION_UP,
                         AKEY_EVENT_FLAG_FROM_SYSTEM, keyCode, scanCode, keyMetaState, downTime);
      getListener().notifyKey(&args);
      ALOGI("device: %s, keyCode=%d, scanCode=%d, eventTime = %lld, action=0x%x,duwnTime=%lld",getDeviceName().c_str(), keyCode, scanCode, args,eventTime, args.action. args.downTime);
  }

KeyboardInputMapper.cpp 是在Android R之后添加的工具,如果是比較舊的版本,需要在InputReader.cpp中添加log。此處可以確定input event被發送到了inputReader了,這里的值就是從getEvent讀取的,如果getEvent的值是對的,但這里沒有打印log,就需要打印cpp文件的callstack,看看是流程中哪一步出錯。

Step4. 檢查inputDispatcher的狀態是否正常

可以通過adb命令來查看inputDispatcher的狀態

adb shell dumpsys input

/frameworks/native/services/inputflinger/dispatcher/InputDispatcher.cpp

  void InputDispatcher::dumpDispatchStateLocked(std::string& dump) {
      dump += StringPrintf(INDENT "DispatchEnabled: %s\n", toString(mDispatchEnabled));
      dump += StringPrintf(INDENT "DispatchFrozen: %s\n", toString(mDispatchFrozen));
      dump += StringPrintf(INDENT "InputFilterEnabled: %s\n", toString(mInputFilterEnabled));
      dump += StringPrintf(INDENT "FocusedDisplayId: %" PRId32 "\n", mFocusedDisplayId);

DispatcherEnabled 必須為1,并且DispatcherFrozen 必須為0,如果是inputDispatcher狀態有問題,需要在代碼中查看哪些地方有修改inputDispatcher的狀態mDispatchEnabled,mDispatchFrozen,找到將修改狀態的地方來分析問題。如果打印出來的FocusedDisplayId或FocusedApplications不符合預期,那就是display or WMS相關問題,與input流程沒有關系。

Step5. 查看最終input消費event的是哪個頁面

/frameworks/base/core/java/android/view/View.java

      public boolean dispatchKeyEvent(KeyEvent event) {
          if (mInputEventConsistencyVerifier != null) {
              mInputEventConsistencyVerifier.onKeyEvent(event, 0);
          }
     Log.i(">_<!!","dispatchKeyEvent event:" + event + " to :" + v);
          // Give any attached key listener a first crack at the event.
          //noinspection SimplifiableIfStatement
          ListenerInfo li = mListenerInfo;
          if (li != null && li.mOnKeyListener != null && (mViewFlags & ENABLED_MASK) == ENABLED
                  && li.mOnKeyListener.onKey(this, event.getKeyCode(), event)) {
              //表明input被消費了
              Log.i(">_<!!","Event:" + event+ " handle in: " + v 
                  + " ,ListenerInfo = " + li.toString());
              return true;
          }
          if (event.dispatch(this, mAttachInfo != null
                  ? mAttachInfo.mKeyDispatchState : null, this)) {
              return true;
          }
          if (mInputEventConsistencyVerifier != null) {
              mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
          }
          return false;
      }

這里的log可以表明input event正在按照view的層級依次dispatch并最終被哪個view消費,如果這個view并不是所期望的view,那么就需要查看為什么消費到這個view上面了,是layout區域有透明邊界?還是期望的view并不存在,可能性就很多,細節可以再深思下。如果這里的view是符合期望的,那么問題就回到應用層了,看應用層對此input事件的響應是否有異常。

原文鏈接:https://juejin.cn/post/7168870464301826055

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