void TransactionCompletedListener::onTransactionCompleted(ListenerStats listenerStats) {
    std::unordered_map<CallbackId, CallbackTranslation, CallbackIdHash> callbacksMap;
    std::multimap<int32_t, sp<JankDataListener>> jankListenersMap;
    {
        std::lock_guard<std::mutex> lock(mMutex);

        /* This listener knows all the sp<IBinder> to sp<SurfaceControl> for all its registered
         * callbackIds, except for when Transactions are merged together. This probably cannot be
         * solved before this point because the Transactions could be merged together and applied in
         * a different process.
         *
         * Fortunately, we get all the callbacks for this listener for the same frame together at
         * the same time. This means if any Transactions were merged together, we will get their
         * callbacks at the same time. We can combine all the sp<IBinder> to sp<SurfaceControl> maps
         * for all the callbackIds to generate one super map that contains all the sp<IBinder> to
         * sp<SurfaceControl> that could possibly exist for the callbacks.
         */
        callbacksMap = mCallbacks;
        jankListenersMap = mJankListeners;
        for (const auto& transactionStats : listenerStats.transactionStats) {
            for (auto& callbackId : transactionStats.callbackIds) {
                mCallbacks.erase(callbackId);
            }
        }
    }

• mCallbacks 拷贝到 callbacksMap。
• 遍历 listenerStats 中的 cllbackId，从 mCallbacks 中移除，因为下面就会处理这些 callbackId。

    for (const auto& transactionStats : listenerStats.transactionStats) {
        // handle on commit callbacks
        for (auto callbackId : transactionStats.callbackIds) {
            if (callbackId.type != CallbackId::Type::ON_COMMIT) {
                continue;
            }
            auto& [callbackFunction, callbackSurfaceControls] = callbacksMap[callbackId];
            if (!callbackFunction) {
                ALOGE("cannot call null callback function, skipping");
                continue;
            }
            std::vector<SurfaceControlStats> surfaceControlStats;
            for (const auto& surfaceStats : transactionStats.surfaceStats) {
                surfaceControlStats
                        .emplace_back(callbacksMap[callbackId]
                                              .surfaceControls[surfaceStats.surfaceControl],
                                      transactionStats.latchTime, surfaceStats.acquireTime,
                                      transactionStats.presentFence,
                                      surfaceStats.previousReleaseFence, surfaceStats.transformHint,
                                      surfaceStats.eventStats, surfaceStats.currentMaxAcquiredBufferCount);
            }

            callbackFunction(transactionStats.latchTime, transactionStats.presentFence,
                             surfaceControlStats);
        }

• 遍历 TransactionStats。先处理类型是 ON_COMMIT 的 CallbackId。
• 从 callbacksMap 根据 callbackId 查找 callbackFunction，如果没有找到，则 continue。
• 如果找到了 callbackFunction，则遍历 SurfaceStats，创建 SurfaceControlStats 加入 surfaceControlStats。
• 调用 callbackFunction()。BLASTBufferQueue 中指向的是 transactionCommittedCallbackThunk。

        // handle on complete callbacks
        for (auto callbackId : transactionStats.callbackIds) {
            if (callbackId.type != CallbackId::Type::ON_COMPLETE) {
                continue;
            }
            auto& [callbackFunction, callbackSurfaceControls] = callbacksMap[callbackId];
            if (!callbackFunction) {
                ALOGE("cannot call null callback function, skipping");
                continue;
            }
            std::vector<SurfaceControlStats> surfaceControlStats;
            for (const auto& surfaceStats : transactionStats.surfaceStats) {
                surfaceControlStats
                        .emplace_back(callbacksMap[callbackId]
                                              .surfaceControls[surfaceStats.surfaceControl],
                                      transactionStats.latchTime, surfaceStats.acquireTime,
                                      transactionStats.presentFence,
                                      surfaceStats.previousReleaseFence, surfaceStats.transformHint,
                                      surfaceStats.eventStats, surfaceStats.currentMaxAcquiredBufferCount);
                if (callbacksMap[callbackId].surfaceControls[surfaceStats.surfaceControl]) {
                    callbacksMap[callbackId]
                            .surfaceControls[surfaceStats.surfaceControl]
                            ->setTransformHint(surfaceStats.transformHint);
                }
                // If there is buffer id set, we look up any pending client release buffer callbacks
                // and call them. This is a performance optimization when we have a transaction
                // callback and a release buffer callback happening at the same time to avoid an
                // additional ipc call from the server.
                if (surfaceStats.previousReleaseCallbackId != ReleaseCallbackId::INVALID_ID) {
                    ReleaseBufferCallback callback;
                    {
                        std::scoped_lock<std::mutex> lock(mMutex);
                        callback = popReleaseBufferCallbackLocked(
                                surfaceStats.previousReleaseCallbackId);
                    }
                    if (callback) {
                        callback(surfaceStats.previousReleaseCallbackId,
                                 surfaceStats.previousReleaseFence
                                         ? surfaceStats.previousReleaseFence
                                         : Fence::NO_FENCE,
                                 surfaceStats.transformHint,
                                 surfaceStats.currentMaxAcquiredBufferCount);
                    }
                }
            }

            callbackFunction(transactionStats.latchTime, transactionStats.presentFence,
                             surfaceControlStats);
        }

• 处理类型是 ON_COMPLETE 的 CallbackId。
• 处理流程基本与 ON_COMMIT 类型类似，只是多了一个 previousReleaseCallbackId 的处理。
• 如果 previousReleaseCallbackId 不等于 INVALID_ID，则调用 TransactionCompletedListener::popReleaseBufferCallbackLocked() 获取 ReleaseCallbackId 对应的 callback，如果存在，则调用，它是 releaseBufferCallbackThunk()。
• 调用 callbackFunction()。BLASTBufferQueue 中函数指向的是 transactionCallbackThunk()。