如何更新RecyclerView适配器数据

392

我正在尝试找出更新 RecyclerView 适配器的问题。

当我获取到新产品列表时,我尝试:

  1. Update the ArrayList from the fragment where recyclerView is created, set new data to adapter, and then call adapter.notifyDataSetChanged(); it did not work.

  2. Create a new adapter, as others did, and it worked for them, but there wasn't any change for me: recyclerView.setAdapter(new RecyclerViewAdapter(newArrayList))

  3. Create a method in Adapter which updates the data as follows:

     public void updateData(ArrayList<ViewModel> viewModels) {
        items.clear();
        items.addAll(viewModels);
        notifyDataSetChanged();
     }
    

    Then I call this method whenever I want to update the data list; it did not work.

  4. To check if I can modify the recyclerView in any way, and I tried to remove at least an item:

      public void removeItem(int position) {
         items.remove(position);
         notifyItemRemoved(position);
     }
    

一切都保持不变。

这是我的适配器:

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> implements View.OnClickListener {

    private ArrayList<ViewModel> items;
    private OnItemClickListener onItemClickListener;

    public RecyclerViewAdapter(ArrayList<ViewModel> items) {
        this.items = items;
    }


    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler, parent, false);
        v.setOnClickListener(this);
        return new ViewHolder(v);
    }

    public void updateData(ArrayList<ViewModel> viewModels) {
        items.clear();
        items.addAll(viewModels);
        notifyDataSetChanged();
    }
    public void addItem(int position, ViewModel viewModel) {
        items.add(position, viewModel);
        notifyItemInserted(position);
    }

    public void removeItem(int position) {
        items.remove(position);
        notifyItemRemoved(position);
    }


    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        ViewModel item = items.get(position);
        holder.title.setText(item.getTitle());
        Picasso.with(holder.image.getContext()).load(item.getImage()).into(holder.image);
        holder.price.setText(item.getPrice());
        holder.credit.setText(item.getCredit());
        holder.description.setText(item.getDescription());

        holder.itemView.setTag(item);
    }


    @Override
    public int getItemCount() {
        return items.size();
    }


    @Override
    public void onClick(final View v) {
        // Give some time to the ripple to finish the effect
        if (onItemClickListener != null) {
            new Handler().postDelayed(new Runnable() {
                @Override
                public void run() {
                    onItemClickListener.onItemClick(v, (ViewModel) v.getTag());
                }
            }, 0);
        }
    }

    protected static class ViewHolder extends RecyclerView.ViewHolder {
        public ImageView image;
        public TextView price, credit, title, description;

        public ViewHolder(View itemView) {
            super(itemView);
            image = (ImageView) itemView.findViewById(R.id.image);
            price = (TextView) itemView.findViewById(R.id.price);
            credit = (TextView) itemView.findViewById(R.id.credit);
            title = (TextView) itemView.findViewById(R.id.title);
            description = (TextView) itemView.findViewById(R.id.description);
        }
    }

    public interface OnItemClickListener {

        void onItemClick(View view, ViewModel viewModel);

    }
}

我按照以下方式初始化RecyclerView

recyclerView = (RecyclerView) view.findViewById(R.id.recycler);
recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 5));
adapter = new RecyclerViewAdapter(items);
adapter.setOnItemClickListener(this);
recyclerView.setAdapter(adapter);

那么,我该如何更新适配器数据以显示新接收到的项目?


问题在于 gridView 所在的布局如下所示:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:tag="catalog_fragment"
    android:layout_height="match_parent">

    <FrameLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:clipToPadding="false"/>

        <ImageButton
            android:id="@+id/fab"
            android:layout_gravity="top|end"
            style="@style/FabStyle"/>

    </FrameLayout>
</LinearLayout>

然后我只需删除LinearLayout,并将FrameLayout作为父布局。


1
items.clear(); items.addAll(newItems); 这是一个丑陋的模式。如果你真的需要在这里进行防御性复制,那么 items = new ArrayList(newItems); 会更好看一些。 - Miha_x64
3
你是对的 - 这样会不那么丑陋。问题在于,这并行不起作用。适配器没有引用参考,它得到的是引用本身。因此,如果你构建一个新数据集,它有一个新的引用,而适配器仍然只知道旧的引用。 - The incredible Jan
16个回答

3

这些方法是高效的,适合开始使用基本的RecyclerView

private List<YourItem> items;

public void setItems(List<YourItem> newItems)
{
    clearItems();
    addItems(newItems);
}

public void addItem(YourItem item, int position)
{
    if (position > items.size()) return;

    items.add(item);
    notifyItemInserted(position);
}

public void addMoreItems(List<YourItem> newItems)
{
    int position = items.size() + 1;
    newItems.addAll(newItems);
    notifyItemChanged(position, newItems);
}

public void addItems(List<YourItem> newItems)
{
    items.addAll(newItems);
    notifyDataSetChanged();
}

public void clearItems()
{
    items.clear();
    notifyDataSetChanged();
}

public void addLoader()
{
    items.add(null);
    notifyItemInserted(items.size() - 1);
}

public void removeLoader()
{
    items.remove(items.size() - 1);
    notifyItemRemoved(items.size());
}

public void removeItem(int position)
{
    if (position >= items.size()) return;

    items.remove(position);
    notifyItemRemoved(position);
}

public void swapItems(int positionA, int positionB)
{
    if (positionA > items.size()) return;
    if (positionB > items.size()) return;

    YourItem firstItem = items.get(positionA);

    videoList.set(positionA, items.get(positionB));
    videoList.set(positionB, firstItem);

    notifyDataSetChanged();
}

您可以在适配器类中实现它们,也可以在片段或活动中实现,但在这种情况下,您必须实例化适配器以调用通知方法。在我的情况下,我通常将其实现在适配器中。


2

我强烈建议您使用[DiffUtil.ItemCallback][1]来处理RecyclerView.Adapter中的更改:

fun setData(data: List<T>) {
    val calculateDiff = DiffUtil.calculateDiff(DiffUtilCallback(items, data))
    items.clear()
    items += data
    calculateDiff.dispatchUpdatesTo(this)
}

在幕后,它通过AdapterListUpdateCallback处理大部分事情:

/**
 * ListUpdateCallback that dispatches update events to the given adapter.
 *
 * @see DiffUtil.DiffResult#dispatchUpdatesTo(RecyclerView.Adapter)
 */
public final class AdapterListUpdateCallback implements ListUpdateCallback {
    @NonNull
    private final RecyclerView.Adapter mAdapter;

    /**
     * Creates an AdapterListUpdateCallback that will dispatch update events to the given adapter.
     *
     * @param adapter The Adapter to send updates to.
     */
    public AdapterListUpdateCallback(@NonNull RecyclerView.Adapter adapter) {
        mAdapter = adapter;
    }

    /** {@inheritDoc} */
    @Override
    public void onInserted(int position, int count) {
        mAdapter.notifyItemRangeInserted(position, count);
    }

    /** {@inheritDoc} */
    @Override
    public void onRemoved(int position, int count) {
        mAdapter.notifyItemRangeRemoved(position, count);
    }

    /** {@inheritDoc} */
    @Override
    public void onMoved(int fromPosition, int toPosition) {
        mAdapter.notifyItemMoved(fromPosition, toPosition);
    }

    /** {@inheritDoc} */
    @Override
    public void onChanged(int position, int count, Object payload) {
        mAdapter.notifyItemRangeChanged(position, count, payload);
    }
}


2

使用 Kotlin 时,我会使用 Adapter。

class ProductAdapter(var apples: List<Apples>?= null) : RecyclerView.Adapter<ProductViewHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ProductViewHolder {...}

    override fun onBindViewHolder(holder: ProductViewHolder, position: Int) {...}

    override fun getItemCount(): Int {...}

    fun setData(newApples: List<Apples>) {
        apples = newApples
    }
}

在Fragment/Activity中

val appleAdapter = ProductAdapter()

val recyclerView = binding.appleRecycler // or findViewById or synthetics or whatever. 
recyclerView.adapter = appleAdapter
recyclerView.layoutManager = LinearLayoutManager(requireContext())

现在处理片段中的数据更改

fun updateRecyclerData(apples: List<Apples>){
    adapter.setData(apples)
    adapter.notifyDataSetChanged()
}

updateRecyclerData(applesList)

这是目前最好的一个。 - Ticherhaz FreePalestine

1

这个工作得很好,试一试。

  ArrayList.remove(position);
  notifyItemRemoved(position);
  notifyDataSetChanged();

你的回答可以通过提供更多支持信息来改进。请编辑以添加进一步的细节,例如引用或文档,以便他人可以确认你的答案是正确的。您可以在帮助中心找到有关如何编写良好答案的更多信息。 - Community

1

我花了很长时间才得到答案:

SELECTEDROW.add(dt);
notifyItemInserted(position);
SELECTEDROW.remove(position);
notifyItemRemoved(position);

需要解释一下。 - Peter Mortensen

0

如果以上评论中没有提到的方法对您无效,那么问题可能出在其他地方。

我发现解决方法之一是我设置适配器列表的方式。在我的活动中,该列表是一个实例变量,当任何数据更改时,我直接更改它。由于它是一个引用变量,所以有些奇怪的事情发生了。

因此,我将引用变量更改为本地变量,并使用另一个变量更新数据,然后传递给先前答案中提到的addAll()函数。


网页内容由stack overflow 提供, 点击上面的
可以查看英文原文,
原文链接