问题描述
我正在使用来自独立表的2个LiveData到应用程序的存储库中。我将两个LiveData作为源添加到扩展CustomMediatorLiveData的{{1}}类中。
在每个MediatorLiveData的{{1}}方法的onChanged回调中，我将两个addSource的值发送到组合了两者并返回单个{{1} }设置为LiveData对象的LiveData。我正在我的存储库中创建此LiveData的对象，并将两个value传递为构造函数的参数。
这会运行并且不会出现任何错误，但是会弄乱LiveData本身中的数据。
示例：如果该日期最初是2020年8月15日，则可能是0001年8月14日。
CustomMediatorLiveData：
CustomMediatorLiveDataNote Repository类：
CustomMediatorLiveData我尝试使用LiveData对象，并将两个public class CustomMediatorLiveData extends MediatorLiveData<List<Object>> {
private List<Note> notes = Collections.emptyList();
private List<RecurringTask> recurringTasks = Collections.emptyList();
public CustomMediatorLiveData(LiveData<List<Note>> liveNotes,LiveData<List<RecurringTask>> liveRecurringTasks) {
addSource(liveNotes,notes1 -> {
if (notes1 != null) {
this.notes = notes1;
}
setValue(combineData(notes,recurringTasks));
});
addSource(liveRecurringTasks,recurringTasks1 -> {
if (recurringTasks1 != null) {
this.recurringTasks = recurringTasks1;
}
setValue(combineData(notes,recurringTasks));
});
}
// This method adds the 2 lists into one and sorts them based on dates and priority.
private List<Object> combineData(List<Note> notes,List<RecurringTask> recurringTasks) {
List<Object> combinedList = new ArrayList<>();
if (notes != null && !notes.isEmpty())
combinedList.addAll(notes);
if(recurringTasks!=null && !recurringTasks.isEmpty())
combinedList.addAll(recurringTasks);
Collections.sort(combinedList,new Comparator<Object>() {
@Override
public int compare(Object o1,Object o2) {
Date d1,d2;
Note n1 = null,n2 = null;
RecurringTask r1 = null,r2 = null;
if (o1 instanceof Note && o2 instanceof Note) {
int hmm = Boolean.compare(((Note) o2).isPriority(),((Note) o1).isPriority());
if (hmm != 0)
return hmm;
}
if (o1 instanceof Note) {
d1 = ((Note) o1).getEnd_date();
n1 = ((Note) o1);
} else {
d1 = ((RecurringTask) o1).getEnd_date();
r1 = ((RecurringTask) o1);
}
if (o2 instanceof Note) {
d2 = ((Note) o2).getEnd_date();
n2 = ((Note) o2);
} else {
d2 = ((RecurringTask) o2).getEnd_date();
r2 = ((RecurringTask) o2);
}
if (n1 != null) {
if (r2 != null) {
if (n1.isPriority()) {
return -1;
}
}
}
if (n2 != null) {
if (r1 != null) {
if (n2.isPriority()) {
return 1;
}
}
}
long l1 = d1.getTime() - d2.getTime();
if (l1 > 0) {
return 1;
} else if (l1 < 0) {
return -1;
} else {
return 0;
}
}
});
return combinedList;
}
}
源添加到存储库本身中，并且仍然存在相同的问题。
实现此目的的正确方法是什么？如何将2个
public class NoteRepository {
private String DB_NAME = "db_task";
Context context;
private RecurringDao recurringDao;
private LiveData<List<RecurringTask>> upcomingRecurringTasks;
private LiveData<List<Note>> upcomingTasks;
private CustomMediatorLiveData customMediatorLiveData;
private NoteDatabase noteDatabase;
public NoteRepository(Context context) {
noteDatabase = NoteDatabase.getInstance(context);
recurringDao = noteDatabase.recurringDao();
upcomingRecurringTasks = recurringDao.getUpcomingRecurringTask();
upcomingTasks = noteDatabase.daoAccess().fetchUpcomingTasks();
this.context = context;
customMediatorLiveData = new CustomMediatorLiveData(upcomingTasks,upcomingRecurringTasks);
}
public LiveData<List<Object>> getCustomMediatorLiveData() {
return customMediatorLiveData;
}
public LiveData<List<RecurringTask>> getUpcomingRecurringTasks() {
return upcomingRecurringTasks;
}
public LiveData<List<Note>> fetchUpcomingTasks() {
return NoteDatabase.getInstance(context).daoAccess().fetchUpcomingTasks();
}
}
组合成一个可以观察到的MediatorLiveData。
解决方法
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