Question

我是房间和实时数据的新手。我的任务是通过服务获取数据并将其插入会议室数据库中，并通过livedata观察器更新UI，但是每当我执行此任务时，由于livedata的更改（插入，更新或删除），观察器都会调用3次。但是实际上我需要的是在完成所有查询（插入/更新/删除）之后仅调用一次观察者，然后从主线程中删除观察者。请任何人帮助解决

主片段中的观察者初始化：

int updateCount=0; // i don't like to use this count
    public void configureViewModel(){
        SCREEN_ID=SCREEN_NO_ADDRESS_DETAIL;
        viewModel = ViewModelProviders.of(this, viewModelFactory).get(DynamicUIViewModel.class);
        viewModel.init(SCREEN_ID,loanType);
        Observer observer=new Observer() {
            @Override
            public void onChanged(@Nullable Object o) {
                List<DynamicUITable> list=(List<DynamicUITable>)o;
                updateCount++;
                if(updateCount==3) {
                    viewModel.getDynamicUITableLiveData().removeObserver(this); // i want to remove observer without checking this updateCount condition.
                    updateCount=0;
                    updateUI(list);
                }
            }
        };
        viewModel.getDynamicUITableLiveData().observe(getViewLifecycleOwner(), observer);
    }

Repository Class :
 public LiveData<List<DynamicUITable>> init(String screenName,String loanType){
                try {
                    refreshData(screenName,loanType);
                }catch (Exception ex){
                    ex.printStackTrace();
                }
                return  dynamicUIDao.load(screenName);
    }



Service call method :
  private void refreshData(final String screenName,String loanType){
        try{
            executor.execute(()->{
                boolean dataExist = (dynamicUIDao.getTableBasedOnScreen(screenName) != null);

                dynamicUIWebservice.getDynamicUIFromServer(screenName).enqueue(new Callback<List<DynamicUITable>>() {
                    @Override
                    public void onResponse(Call<List<DynamicUITable>> call, Response<List<DynamicUITable>> response) {
                        Log.e("TAG", "DATA REFRESHED FROM NETWORK");
                        executor.execute(()-> {
                            List<DynamicUITable> dynamicUITableList = response.body();
                            if (dynamicUITableList != null) {
                                if (dataExist) {
                                    dynamicUIDao.deleteRecords(screenName);
                                    dynamicUIDao.save(dynamicUITableList);
                                } else {
                                    dynamicUIDao.save(dynamicUITableList);
                                    dynamicUIDao.load(screenName);
                                }
                               /* From here observer is calling whenever live data changes but what i need is , i need to 
                                call observer only one time after completion all query operation*/
                            }
                        });
                    }

                    @Override
                    public void onFailure(Call<List<DynamicUITable>> call, Throwable t) {
                    }
                });
            });
        }catch (Exception ex){
            ex.printStackTrace();
        }
    }

Answer 1

您可以在一个Transaction中运行所有的数据库操作。由于插入，替换和删除将在单个事务中完成，因此这将使您的观察者得到通知。

完成所有查询（插入/更新/删除）后，是否只能调用观察者一次？

1 个答案: