找不到接受参数类型 'androidx.lifecycle.LiveData< 的 ~ItemBinding~ 的设置器

Question

找不到二传手 那 接受参数类型 'androidx.lifecycle.LiveData' 如果绑定适配器提供了设置器，请检查适配器是否 注释正确且参数类型匹配。

两天多来，我一直在逐行浏览我的应用程序。我使用 Google 提供的“BasicSample”Android Room 应用程序来模拟我自己的应用程序，但是当我将它包含在我的 dog_fragment.xml 中时出现此错误

<include
 layout="@layout/dog_item"
 app:product="@{dogViewModel.dog}" />

“dog_item”布局（dog_item.xml）用于显示狗的列表，当您单击它时，它将带您进入狗详细信息屏幕（dog_fragment.xml）。没有它，一切都很好，但它缺少在详细信息屏幕中播放的“狗”图块，并且只会显示一个咀嚼玩具列表。

dog_fragment.xml

<?xml version="1.0" encoding="utf-8"?>

<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">
  
  <data>
    <import type="android.view.View" />
    
    <variable
      name="isLoading"
      type="boolean" />
    
    <variable
      name="dog"
      type="the_derek.dogstuff.viewmodel.DogViewModel" />
  </data>
  
  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/cardview_light_background"
    android:orientation="vertical">
    
    <include
      layout="@layout/dog_item"
      app:product="@{dogViewModel.dog}" />
    
    <FrameLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent">
      
      <TextView
        android:id="@+id/tv_loading_chew_toys"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/loading_chew_toys"
        app:visibleGone="@{isLoading}" />
      
      <FrameLayout
        android:id="@+id/chew_toys_list_wrapper"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        
        <androidx.recyclerview.widget.RecyclerView
          android:id="@+id/chew_toy_list"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:contentDescription="@string/cd_chew_toys_list"
          app:layoutManager="LinearLayoutManager"
          app:visibleGone="@{!isLoading}" />
      </FrameLayout>
    </FrameLayout>
  </LinearLayout>
</layout>

DogFragment.java

public class DogFragment extends Fragment {

 private static final String TAG = "\t\tDogFragment";
 private static final String KEY_DOG_ID = "dog_id";

 private final ChewToyClickCallback mChewToyClickCallback =
   chewToy -> {
    // no-op
   };
 private DogFragmentBinding mBinding;
 private ChewToyAdapter mChewToyAdapter;

 public static DogFragment forDog(int dogId) {
  DogFragment fragment = new DogFragment();
  Bundle args = new Bundle();
  args.putInt(KEY_DOG_ID, dogId);
  fragment.setArguments(args);
  return fragment;
 }

 @Nullable
 @Override
 public View onCreateView(
   @NonNull LayoutInflater inflater,
   @Nullable ViewGroup container,
   @Nullable Bundle savedInstanceState) {
  mBinding = DataBindingUtil.inflate(inflater, R.layout.dog_fragment, container, false);
 
  mChewToyAdapter = new ChewToyAdapter(mChewToyClickCallback);
  mBinding.chewToyList.setAdapter(mChewToyAdapter);
  return mBinding.getRoot();
 }

 @Override
 public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
  DogViewModel.Factory factory =
    new DogViewModel.Factory(
      requireActivity().getApplication(), requireArguments().getInt(KEY_DOG_ID));
  final DogViewModel model =
    new ViewModelProvider(this, factory).get(DogViewModel.class);

  mBinding.setLifecycleOwner(getViewLifecycleOwner());
  mBinding.setDogViewModel(model);

  subscribeToModel(model);
 }

 private void subscribeToModel(final DogViewModel model) {
  model
    .getChewToys()
    .observe(
      getViewLifecycleOwner(),
      chewToyEntities -> {
       if (chewToyEntities != null) {
        mBinding.setIsLoading(false);
        mChewToyAdapter.submitList(chewToyEntities);
       } else {
        mBinding.setIsLoading(true);
       }
      });
 }

 @Override
 public void onDestroyView() {
  mBinding = null;
  mChewToyAdapter = null;
  super.onDestroyView();
 }
}

DogViewModel.java

public class DogViewModel extends AndroidViewModel {

  private static final String TAG = "\t\tDogViewModel";
  private final LiveData<DogEntity> mObservableDog;
  private final LiveData<List<ChewToyEntity>> mObservableChewToys;

  public DogViewModel(
      @NonNull Application application, DataRepository repository, final int dogId) {
    super(application);
    mObservableChewToys = repository.loadChewToysById(dogId);
    mObservableDog = repository.loadDog(dogId);
  }

  public LiveData<List<ChewToyEntity>> getChewToys() {
    return mObservableChewToys;
  }

  public LiveData<DogEntity> getDog() {
    return mObservableDog;
  }

  public static class Factory extends ViewModelProvider.NewInstanceFactory {

    @NonNull private final Application mApplication;

    private final int mDogId;

    private final DataRepository mRepository;

    public Factory(@NonNull Application application, int dogId) {
      mApplication = application;
      mDogId = dogId;
      mRepository = ((DogApp) application).getRepository();
    }

    @SuppressWarnings("unchecked")
    @Override
    @NonNull
    public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
      return (T) new DogViewModel(mApplication, mRepository, mDogId);
    }
  }
}

BindingAdapters.java

public class BindingAdapters {
  @BindingAdapter("visibleGone")
  public static void showHide(View view, boolean show) {
    view.setVisibility(show ? View.VISIBLE : View.GONE);
  }
}

DogClickCallback.java

public interface DogClickCallback {
 void onClick(Dog dog);
}

道查询

@Query("select * from dog_table where id = :dogId")
LiveData<DogEntity> loadDog(int dogId);

DogAdapter.java

public class DogAdapter extends RecyclerView.Adapter<DogAdapter.DogViewHolder> {
 private static final String TAG = "\t\tDogAdapter";

 @Nullable private final DogClickCallback mDogClickCallback;
 List<? extends Dog> mDogList;

 public DogAdapter(@Nullable DogClickCallback clickCallback) {
   Log.i(TAG, "DogAdapter: public constructor");
   mDogClickCallback = clickCallback;
   setHasStableIds(true);
 }

 public void setDogList(final List<? extends Dog> dogList) {
   if (mDogList == null) {
    mDogList = dogList;
    notifyItemRangeInserted(0, dogList.size());
   } else {
    DiffUtil.DiffResult result =
       DiffUtil.calculateDiff(
          new DiffUtil.Callback() {
            @Override
            public int getOldListSize() {
             return mDogList.size();
            }
            @Override
            public int getNewListSize() {
             return dogList.size();
            }
            @Override
            public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
             return mDogList.get(oldItemPosition).getId()
                == dogList.get(newItemPosition).getId();
            }
            @Override
            public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
             Dog newDog = dogList.get(newItemPosition);
             Dog oldDog = mDogList.get(oldItemPosition);
             return newDog.getId() == oldDog.getId()
                && TextUtils.equals(newDog.getName(), oldDog.getName());
            }
          });
    mDogList = dogList;
    result.dispatchUpdatesTo(this);
   }
 }

 @Override
 @NonNull
 public DogViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
   DogItemBinding binding =
      DataBindingUtil.inflate(
         LayoutInflater.from(parent.getContext()), R.layout.dog_item, parent, false);
   binding.setCallback(mDogClickCallback);
   return new DogViewHolder(binding);
 }

 @Override
 public void onBindViewHolder(@NonNull DogViewHolder holder, int position) {
   holder.binding.setDog(mDogList.get(position));
   holder.binding.executePendingBindings();
 }

 @Override
 public int getItemCount() {
   return mDogList == null ? 0 : mDogList.size();
 }

 @Override
 public long getItemId(int position) {
   return mDogList.get(position).getId();
 }

 static class DogViewHolder extends RecyclerView.ViewHolder {
   final DogItemBinding binding;
   public DogViewHolder(DogItemBinding binding) {
    super(binding.getRoot());
    this.binding = binding;
   }
 }
}

---

---

（DogEntity 也有 Dog 模型类，如果有帮助的话） 我试过无效缓存/重启，我试过清理项目，重建项目。我已经开始了一个新项目并将我的文件复制到其中。 哦，还有，这是一个错误补充：

import the_derek.dogstuff.databinding.DogFragmentBindingImpl;

它告诉我它无法解析 DogFragmentBindingImpl 我不知道它是如何产生的，但我认为这些问题是相互交织的。我不知道我是否错过了任何可以提供帮助的代码，请告诉我。

（仿照） android architecture-components-samples

Answer 1

这是binding adapter 错误。如果您在 XML 中编写“app:product”，则在您的 kotlin 或 java 类之一中必须有一个名为“product”的绑定适配器。例如，对于您的

app:product="@{dogViewModel.dog}"

应该是这样的：

@BindingAdapter("product")
fun yourFunctionName(yourViewType: YourViewType, data: List<DogEntity>?) {
    // your binding code here
}

阅读有关数据绑定和绑定适配器的更多信息。

Answer 2

我花了数周或一个月的时间认为“app:product”是 XML 的某种标准短语或约定。我认为“产品”是一个通用术语，如“重力”或“布局”......如果你明白我在说什么。因为当我发布我是 Android 新手的问题时，我从未想过“app:”后面的术语需要根据数据中的变量进行更改。

<include
     layout="@layout/dog_item"
     app:dog="@{dogViewModel.dog}" />

Answer 3

您在这里传递了一个 LiveData 对象：

app:product="@{dogViewModel.dog}"

你需要传入：

app:product="@{dogViewModel.dog.value}"