分页库过滤/搜索 [英] Paging Library Filter/Search

问题描述

我正在使用 Android 分页库，如下所述:https://developer.android.com/topic/libraries/architecture/paging.html

但我也有一个 EditText 用于按名称搜索用户.

如何过滤 Paging 库中的结果以仅显示匹配的用户?

解决方案

您可以使用 MediatorLiveData 解决此问题.

特别是Transformations.switchMap.

//原代码，后期改进公共无效重新加载任务(){if(liveResults != null) {liveResults.removeObserver(this);}liveResults = getFilteredResults();liveResults.observeForever(this);}

但如果你仔细想想，你应该能够在不使用 observeForever 的情况下解决这个问题，尤其是当我们考虑到 switchMap 也在做类似的事情时.>

所以我们需要的是一个LiveData，它被切换映射到我们需要的LiveData>.

private final MutableLiveDatafilterText = savedStateHandle.getLiveData(filterText")私有最终 LiveData>数据;公共 MyViewModel() {数据 = Transformations.switchMap(过滤文本，(输入)->{if(input == null || input.equals("")) {返回 repository.getData();} 别的 {返回 repository.getFilteredData(input);}}});}公共 LiveData>获取数据(){返回数据；}

通过这种方式，从一个到另一个的实际更改由 MediatorLiveData 处理.

I am using the Android Paging Library like described here: https://developer.android.com/topic/libraries/architecture/paging.html

But i also have an EditText for searching Users by Name.

How can i filter the results from the Paging library to display only matching Users?

解决方案

You can solve this with a MediatorLiveData.

Specifically Transformations.switchMap.

// original code, improved later
public void reloadTasks() {
    if(liveResults != null) {
        liveResults.removeObserver(this);
    }
    liveResults = getFilteredResults();
    liveResults.observeForever(this);
}

But if you think about it, you should be able to solve this without use of observeForever, especially if we consider that switchMap is also doing something similar.

So what we need is a LiveData<SelectedOption> that is switch-mapped to the LiveData<PagedList<T>> that we need.

private final MutableLiveData<String> filterText = savedStateHandle.getLiveData("filterText")

private final LiveData<List<T>> data;

public MyViewModel() {
    data = Transformations.switchMap(
            filterText,
            (input) -> { 
                if(input == null || input.equals("")) { 
                    return repository.getData(); 
                } else { 
                    return repository.getFilteredData(input); }
                }
            });
  }

  public LiveData<List<T>> getData() {
      return data;
  }

This way the actual changes from one to another are handled by a MediatorLiveData.

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