我的Fragment中有一个带有AAC的RecyclerView。 ViewModel - > Repository - > DAO,带有一些自定义查询和一个getAllItems。
我想使用Filter FAB或Spinner来调用getOrderItemList或getWhereItemList查询,但我不知道我该怎么做。
我有一个用于我的SearchView的存储库过滤器,但是是另一回事,现在我想更改列表顺序(按字母顺序排列,年份...)并创建一个WhereCondition,其中包含许多我在对话框中的复选框(例如:我检查“完成“和”操作“复选框并创建字符串whereCondition =”(状态='完成'和类型'%Action%')“)。
如何从我的Fragment调用getWhereItemList和getOrderItemList查询来更改我的RecyclerView内容?
ItemDAO:
@Query("SELECT * from item_table ")
<List<Item>> getItemList();
@Query("SELECT * from item_table ORDER by :order DESC")
<List<Item>> getOrderItemList(String order);
@Query("SELECT * from item_table WHERE :whereCondition")
<List<Item>> getWhereItemList(String whereCondition);
My Fragment使用getAllItems填充RecyclerView:
private ItemViewModel myItemViewModel;
RecyclerView myRecyclerView = findViewById(R.id.recyclerview);
final ItemListAdapter myAdapter = new ItemListAdapter(this);
myRecyclerView.setAdapter(myAdapter);
myRecyclerView.setLayoutManager(new LinearLayoutManager(this));
myItemViewModel = ViewModelProviders.of(this).get(ItemViewModel.class);
myItemViewModel.getAllItems().observe(this, new Observer<List<Item>>() {
@Override
public void onChanged(@Nullable final List<Item> items) {
myAdapter.setItems(items);
}
ItemListAdapter:
private List<Item> myItems;
void setItems(List<Item> items){
myItems = items;
notifyDataSetChanged();
}
ItemViewModel:
private ItemRepository myRepository;
private LiveData<List<Item>> myAllItems;
public ItemViewModel (Application application) {
super(application);
myRepository = new ItemRepository(application);
myAllItems = myRepository.getAllItems();
}
LiveData<List<Item>> getAllItems() { return myAllItems; }
谢谢。
想法是有两个LiveData
实例:
List<Item>
。这也应该对其他LiveData
变化作出反应,并在必要时获得新的List<Item>
。你可以使用Transformations.SwitchMap来实现LiveData2
。它的作用是它基本上返回一个LiveData
实例,可以切换到另一个源以响应另一个LiveData
对象。
ItemViewModel:
private ItemRepository myRepository;
/**
* Keep track of the current filter type.
* In this example the initial value is set to Filter.ALL, which
* represents the non-filtered list.
*/
private MutableLiveData<Filter> itemFilter = new MutableLiveData<>(Filter.ALL);
/**
* Emits list of items
*/
private LiveData<List<Item>> myItems = Transformations.switchMap(itemFilter, filter -> {
// Everytime itemFilter emits a new value, this piece of code
// will be invoked. You are responsible for returning the
// LiveData instance according to the filter value.
switch(filter.type) {
case ALL:
return myRepository.getAllItems();
case ORDER_BY:
return myRepository.getOrderItemList(filter.query);
case WHERE:
return myRepository.getWhereItemList(filter.query);
}
});
public ItemViewModel (Application application) {
super(application);
myRepository = new ItemRepository(application);
}
public LiveData<List<Item>> getItems() { return myItems; }
/**
* View should call this method in order to switch to different
* filter.
*/
public void changeFilter(Filter itemFilter) {
this.itemFilter.setValue(filter);
}
定义此自定义过滤器类:
public class Filter {
public enum Type {
ALL,
ORDER_BY,
WHERE
}
final public Type type;
final public String query;
public Filter(Type type, String query) {
this.type = type;
this.query = query;
}
}