我有以下观察者来监视表更改，当触发更改时，它将调用api来同步用户信息。此逻辑可以完成工作，但是碰巧OnChange调用多次且设置了相同的更改，因此可以进行多个api调用，而这是不需要的。我添加了一个全局列表来捕获inProcess项，但该列表在每个OnChange调用之间均未同步。这是代码：
userViewModel.getAllNewUsers().observe(getActivity(), new Observer<List<User>>() {
@Override
public void onChanged(@Nullable List<User> users) {
Log.d(logTag, "Observeed " + users.size() + " new users, calling updateNewUsers");
List<User> userSyncList = new ArrayList<>();
Log.d(logTag, "userProcessingList size " + userProcessingList.size());
Log.d(logTag, "users size " + users.size());
if (userProcessingList.size() == 0 && users.size() > 0) {
Log.d(logTag, "Nothing is processing, let's sync all users");
userProcessingList.addAll(users);
userSyncList.addAll(users);
Log.d(logTag, "new userProcessingList size " + userProcessingList.size());
Log.d(logTag, "userSyncList " + userProcessingList.toString());
} else if (users.size() > 0) {
for (User user : users) {
if (!userProcessingList.contains(user)) {
Log.d(logTag, "userProcessingList is " + userProcessingList.toString());
userProcessingList.add(user);
userSyncList.add(user);
} else {
Log.d(logTag, "User already in syncing process, ignoring...");
}
}
}
if (userSyncList.size() > 0) {
updateNewUsers(userSyncList);
}
if (users.size() == 0 && userProcessingList.size() > 0) {
Log.d(logTag, "all users are in sync, let empty out the processing list");
userProcessingList.clear();
}
Log.d(logTag, "at the end userProcessingList size " + userProcessingList.size());
}
});
这是日志
09-16 23:35:34.040 5956-5956: Observeed 0 new users, calling updateNewUsers
09-16 23:35:34.040 5956-5956: userProcessingList size 0
09-16 23:35:34.040 5956-5956: users size 0
09-16 23:35:34.040 5956-5956: at the end userProcessingList size 0
09-16 23:35:34.047 5956-5956: Observeed 2 new users, calling updateNewUsers
09-16 23:35:34.047 5956-5956: userProcessingList size 0
09-16 23:35:34.047 5956-5956: users size 2
09-16 23:35:34.048 5956-5956: Nothing is processing, let's sync all users
09-16 23:35:34.048 5956-5956: new userProcessingList size 2 <-- THE LIST SIZE IS NOW 2
09-16 23:35:34.048 5956-5956: in updateViewModelForNewUsers
09-16 23:35:34.048 5956-5956: newUserCounter is -1
09-16 23:35:34.048 5956-5956: isVisible is true
09-16 23:35:34.050 5956-5956: at the end userProcessingList size 2 <-- THE LIST IS STILL 2
09-16 23:35:34.050 5956-5956: Observeed 2 new users, calling updateNewUsers
09-16 23:35:34.050 5956-5956: userProcessingList size 0 <-- LIST SIZE IS NOW 0 WHILE IT SHOULD BE 2
09-16 23:35:34.050 5956-5956: users size 2
09-16 23:35:34.050 5956-5956: Nothing is processing, let's sync all users
09-16 23:35:34.050 5956-5956: new userProcessingList size 2
09-16 23:35:34.050 5956-5956: in updateViewModelForNewUsers
09-16 23:35:34.050 5956-5956: newUserCounter is 0
09-16 23:35:34.050 5956-5956: isVisible is true
The list size will eventually be 2 after couple OnChange is called.
我尝试使用CopyOnWriteArrayList，并使用Synchorized（userProcessingList）{}收集collect.synchronizedList，但两者都无济于事。请指教！