class ListenerCallbacks {
public:
    ListenerCallbacks(const sp<IBinder>& listener,
                      const std::unordered_set<CallbackId, CallbackIdHash>& callbacks)
          : transactionCompletedListener(listener),
            callbackIds(callbacks.begin(), callbacks.end()) {}

    ListenerCallbacks(const sp<IBinder>& listener, const std::vector<CallbackId>& ids)
          : transactionCompletedListener(listener), callbackIds(ids) {}

    bool operator==(const ListenerCallbacks& rhs) const {
        if (transactionCompletedListener != rhs.transactionCompletedListener) {
            return false;
        }
        if (callbackIds.empty()) {
            return rhs.callbackIds.empty();
        }
        return callbackIds.front().id == rhs.callbackIds.front().id;
    }

    // Returns a new ListenerCallbacks filtered by type
    ListenerCallbacks filter(CallbackId::Type type) const;

    sp<IBinder> transactionCompletedListener;
    std::vector<CallbackId> callbackIds;
};

• transactionCompletedListener 是 ITransactionCompletedListener。
• callbackIds 是 CallbackId 向量。

Transaction::mListenerCallbacks 是 ITransactionCompletedListener → CallbackInfo map。