android - 如何在 RecyclerView 中将 SortedList 与 Android 数据绑定库一起使用？

Question

Android 数据绑定提供了几个 Observable 数据接口，包括 ObservableList。但是 SortedList（在 RecyclerView 库的最新版本中引入）根本没有扩展 List。

如何将 SortedList 用于带有 Android 数据绑定库的 RecyclerView？

Answer 1

受 George Mount 的启发，我实现了我的 ObservableSortedList 版本，它具有原始 SortedList 的全部功能，包括：

• 批量更新。只需调用 SortedList 的 beginBatchedUpdates() 和 endBatchedUpdates() 即可。
• 去重和智能刷新。构造函数中的回调负责排序、去重和内容区分。

完整代码：

public class ObservableSortedList<T> extends AbstractList<T> implements ObservableList<T> {

  /** @see android.support.v7.util.SortedList.Callback */
  public interface Callback<T2> {
    /** @see android.support.v7.util.SortedList.Callback#compare(Object, Object) */
    int compare(T2 o1, T2 o2);
    /** @see android.support.v7.util.SortedList.Callback#areItemsTheSame(Object, Object) */
    boolean areItemsTheSame(T2 item1, T2 item2);
    /** @see android.support.v7.util.SortedList.Callback#areContentsTheSame(Object, Object) */
    boolean areContentsTheSame(T2 oldItem, T2 newItem);
  }

  public ObservableSortedList(final Class<T> klass, final Callback<T> callback) {
    mList = new SortedList<>(klass, new CallbackWrapper<>(callback));
  }

  /** @see SortedList#beginBatchedUpdates() */
  public void beginBatchedUpdates() { mList.beginBatchedUpdates(); }
  /** @see SortedList#endBatchedUpdates() */
  public void endBatchedUpdates() { mList.endBatchedUpdates(); }

  @Override public boolean add(final T item) {
    sTlsUpdated.set(false);
    mList.add(item);
    return sTlsUpdated.get();   // May be set by Callback.onInserted() or onChanged().
  }

  @Override public T set(final int location, final T object) {
    final T old = mList.get(location);
    mList.updateItemAt(location, cast(object));
    return old;
  }

  @Override public int indexOf(final Object object) {
    try {
      return mList.indexOf(cast(object));
    } catch (final ClassCastException ignored) {
      return -1;
    }
  }

  @Override public boolean remove(final Object object) {
    try {
      return mList.remove(cast(object));
    } catch (final ClassCastException ignored) {
      return false;
    }
  }

  @SuppressWarnings("unchecked") private T cast(final Object object) { return (T) object; }

  @Override public boolean contains(final Object object) { return indexOf(object) != SortedList.INVALID_POSITION; }
  @Override public T get(final int location) { return mList.get(location); }
  @Override public int size() { return mList.size(); }
  @Override public void clear() { mList.clear(); }
  @Override public T remove(final int location) { return mList.removeItemAt(location); }

  /* ObservableList */

  @Override public void addOnListChangedCallback(final OnListChangedCallback<? extends ObservableList<T>> callback) {
    if (mListeners == null) this.mListeners = new ListChangeRegistry();
    mListeners.add(callback);
  }

  @Override public void removeOnListChangedCallback(final OnListChangedCallback<? extends ObservableList<T>> callback) {
    if (mListeners == null) return;
    mListeners.remove(callback);
  }

  private final SortedList<T> mList;
  private static final ThreadLocal<Boolean> sTlsUpdated = new ThreadLocal<>();
  private transient @Nullable ListChangeRegistry mListeners = new ListChangeRegistry();

  public class CallbackWrapper<T2> extends SortedList.Callback<T2> {

    @Override public final void onInserted(final int position, final int count) {
      sTlsUpdated.set(true);
      if (mListeners != null) mListeners.notifyInserted(ObservableSortedList.this, position, count);
    }

    @Override public final void onRemoved(final int position, final int count) {
      if (mListeners != null) mListeners.notifyRemoved(ObservableSortedList.this, position, count);
    }

    @Override public final void onMoved(final int fromPosition, final int toPosition) {
      if (mListeners != null) mListeners.notifyMoved(ObservableSortedList.this, fromPosition, toPosition, 1);
    }

    @Override public final void onChanged(final int position, final int count) {
      sTlsUpdated.set(true);
      if (mListeners != null) mListeners.notifyChanged(ObservableSortedList.this, position, count);
    }

    @Override public int compare(final T2 o1, final T2 o2) { return mCallback.compare(o1, o2); }
    @Override public boolean areContentsTheSame(final T2 oldItem, final T2 newItem) { return mCallback.areContentsTheSame(oldItem, newItem); }
    @Override public boolean areItemsTheSame(final T2 item1, final T2 item2) { return mCallback.areItemsTheSame(item1, item2); }
    public CallbackWrapper(final Callback<T2> callback) { mCallback = callback; }

    private final Callback<T2> mCallback;
  }
}

Answer 2

要使 SortedList 在数据绑定中支持可观察性，您必须自己实现接口。由于 API 中存在冲突，看来您必须包装它。像这样的东西：

public class ObservableSortedList<T> implements ObservableList<T> {
    private final SortedList<T> mList;
    private final ListChangeRegistry mListeners = new ListChangeRegistry();

    @Override
    public boolean add(T item) {
        int index = mList.add(item);
        mListeners.notifyInserted(this, index, 1);
    }

    @Observable
    public void addOnListChangedCallback(OnListChangedCallback<? extends ObservableList<T>> callback) {
        mListeners.add(callback);
    }

    ...
}