如何更新RecyclerView适配器数据？

Question

试图找出更新RecyclerView适配器的问题.

在我获得新的产品列表后,我尝试:

1. 更新创建ArrayList的片段recyclerView,将新数据设置为适配器,然后调用adapter.notifyDataSetChanged(); 那没起效.

2. 像其他人一样创建一个新的适配器,它适用于他们,但对我没有任何改变: recyclerView.setAdapter(new RecyclerViewAdapter(newArrayList))

3. 创建一个Adapter更新数据的方法,如下所示:

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

   然后每当我想更新数据列表时,我都会调用此方法; 那没起效.

4. 要检查我是否可以以任何方式修改recyclerView,并且我尝试删除至少一个项目:

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

   一切都保持原样.

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);

    }
}

我发起RecyclerView如下:

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,我如何实际更新适配器数据以显示新收到的项目？

---

更新:问题是gridView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>

然后我只是删除LinearLayout并FrameLayout作为父布局.

Answer 1

我正在使用RecyclerView,删除和更新工作都很顺利.

1)删除:从RecyclerView中删除项目有4个步骤

list.remove(position);
recycler.removeViewAt(position);
mAdapter.notifyItemRemoved(position);                 
mAdapter.notifyItemRangeChanged(position, list.size());

这些代码对我有用.

2)更新数据:我唯一需要做的就是

mAdapter.notifyDataSetChanged();

您必须在Actvity/Fragment代码中执行所有这些操作,而不是在RecyclerView适配器代码中.

Answer 2

这是未来访客的一般答案.解释了更新适配器数据的各种方法.该过程每次包括两个主要步骤:

1. 更新数据集
2. 通知适配器更改

插入单个项目

在索引处添加"Pig" 2.

String item = "Pig";
int insertIndex = 2;
data.add(insertIndex, item);
adapter.notifyItemInserted(insertIndex);

插入多个项目

在指数处再插入三只动物2.

ArrayList<String> items = new ArrayList<>();
items.add("Pig");
items.add("Chicken");
items.add("Dog");
int insertIndex = 2;
data.addAll(insertIndex, items);
adapter.notifyItemRangeInserted(insertIndex, items.size());

删除单个项目

从列表中删除"Pig".

int removeIndex = 2;
data.remove(removeIndex);
adapter.notifyItemRemoved(removeIndex);

删除多个项目

从列表中删除"Camel"和"Sheep".

int startIndex = 2; // inclusive
int endIndex = 4;   // exclusive
int count = endIndex - startIndex; // 2 items will be removed
data.subList(startIndex, endIndex).clear();
adapter.notifyItemRangeRemoved(startIndex, count);

删除所有项目

清除整个列表.

data.clear();
adapter.notifyDataSetChanged();

用新列表替换旧列表

清除旧列表然后添加一个新列表.

// clear old list
data.clear();

// add new list
ArrayList<String> newList = new ArrayList<>();
newList.add("Lion");
newList.add("Wolf");
newList.add("Bear");
data.addAll(newList);

// notify adapter
adapter.notifyDataSetChanged();

它adapter有一个引用data,所以重要的是我没有设置data为新对象.相反,我清除了旧项目data,然后添加了新项目.

更新单个项目

更改"羊"项目,使其显示"我喜欢羊".

String newValue = "I like sheep.";
int updateIndex = 3;
data.set(updateIndex, newValue);
adapter.notifyItemChanged(updateIndex);

移动单个项目

将"羊"从一个位置移动3到另一个位置1.

int fromPosition = 3;
int toPosition = 1;

// update data array
String item = data.get(fromPosition);
data.remove(fromPosition);
data.add(toPosition, item);

// notify adapter
adapter.notifyItemMoved(fromPosition, toPosition);

码

这是项目代码供您参考.可以在此答案中找到RecyclerView适配器代码.

MainActivity.java

public class MainActivity extends AppCompatActivity implements MyRecyclerViewAdapter.ItemClickListener {

    List<String> data;
    MyRecyclerViewAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // data to populate the RecyclerView with
        data = new ArrayList<>();
        data.add("Horse");
        data.add("Cow");
        data.add("Camel");
        data.add("Sheep");
        data.add("Goat");

        // set up the RecyclerView
        RecyclerView recyclerView = findViewById(R.id.rvAnimals);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),
                layoutManager.getOrientation());
        recyclerView.addItemDecoration(dividerItemDecoration);
        adapter = new MyRecyclerViewAdapter(this, data);
        adapter.setClickListener(this);
        recyclerView.setAdapter(adapter);
    }

    @Override
    public void onItemClick(View view, int position) {
        Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
    }

    public void onButtonClick(View view) {
        insertSingleItem();
    }

    private void insertSingleItem() {
        String item = "Pig";
        int insertIndex = 2;
        data.add(insertIndex, item);
        adapter.notifyItemInserted(insertIndex);
    }

    private void insertMultipleItems() {
        ArrayList<String> items = new ArrayList<>();
        items.add("Pig");
        items.add("Chicken");
        items.add("Dog");
        int insertIndex = 2;
        data.addAll(insertIndex, items);
        adapter.notifyItemRangeInserted(insertIndex, items.size());
    }

    private void removeSingleItem() {
        int removeIndex = 2;
        data.remove(removeIndex);
        adapter.notifyItemRemoved(removeIndex);
    }

    private void removeMultipleItems() {
        int startIndex = 2; // inclusive
        int endIndex = 4;   // exclusive
        int count = endIndex - startIndex; // 2 items will be removed
        data.subList(startIndex, endIndex).clear();
        adapter.notifyItemRangeRemoved(startIndex, count);
    }

    private void removeAllItems() {
        data.clear();
        adapter.notifyDataSetChanged();
    }

    private void replaceOldListWithNewList() {
        // clear old list
        data.clear();

        // add new list
        ArrayList<String> newList = new ArrayList<>();
        newList.add("Lion");
        newList.add("Wolf");
        newList.add("Bear");
        data.addAll(newList);

        // notify adapter
        adapter.notifyDataSetChanged();
    }

    private void updateSingleItem() {
        String newValue = "I like sheep.";
        int updateIndex = 3;
        data.set(updateIndex, newValue);
        adapter.notifyItemChanged(updateIndex);
    }

    private void moveSingleItem() {
        int fromPosition = 3;
        int toPosition = 1;

        // update data array
        String item = data.get(fromPosition);
        data.remove(fromPosition);
        data.add(toPosition, item);

        // notify adapter
        adapter.notifyItemMoved(fromPosition, toPosition);
    }
}

笔记

• 如果使用notifyDataSetChanged(),则不会执行任何动画.这也可能是一项昂贵的操作,因此notifyDataSetChanged()如果您只更新单个项目或一系列项目,则不建议使用此操作.
• 如果要对列表进行大型或复杂的更改,请查看DiffUtil.

进一步研究

• CodePath:使用RecyclerView
• 使用DiffUtil更新RecyclerView的智能方法

Answer 3

这对我有用:

recyclerView.setAdapter(new RecyclerViewAdapter(newList));
recyclerView.invalidate();

创建一个包含更新列表的新适配器(在我的情况下,它是一个转换为ArrayList的数据库)并将其设置为适配器后,我尝试了recyclerView.invalidate()它的工作原理.

Answer 4

您有两个选项可以执行此操作:从适配器刷新UI:

mAdapter.notifyDataSetChanged();

或者从recyclerView本身刷新它:

recyclerView.invalidate();

Answer 5

另一种选择是使用diffutil.它会将原始列表与新列表进行比较,如果有更改,则使用新列表作为更新.

基本上,我们可以使用DiffUtil来比较旧数据和新数据,并让它代表您调用notifyItemRangeRemoved和notifyItemRangeChanged以及notifyItemRangeInserted.

使用diffUtil而不是notifyDataSetChanged的简单示例:

DiffResult diffResult = DiffUtil
                .calculateDiff(new MyDiffUtilCB(getItems(), items));

//any clear up on memory here and then
diffResult.dispatchUpdatesTo(this);

//and then, if necessary
items.clear()
items.addAll(newItems)

如果它是一个很大的列表,我会在主线程中执行calculateDiff工作.

Answer 6

更新listview,gridview和recyclerview的数据

mAdapter.notifyDataSetChanged();

要么

mAdapter.notifyItemRangeChanged(0, itemList.size());

Answer 7

我建议您探索DiffUtil。它还提高了 RecyclerView 在处理列表更新时的性能。

1. 在适配器中定义一个变量：

    differList = AsyncListDiffer(this, this.callback);     
    differList.submitList(list)
   

在这里，列表可以是您的初始原始列表，也可以只是一个空列表，前提是您稍后将更新它。

2. 实现回调：

   private val callback : DiffUtil.ItemCallback<Item> = object: DiffUtil.ItemCallback<Item>() {
   
      override fun areItemsTheSame(oldItem: Item, newItem: Item) =
        oldItem.id == newItem.id
   
      override fun areContentsTheSame(oldItem: Item, newItem: Item) =
        oldItem == newItem
    }
   

3. 此外，在同一个适配器中，您将有一些公共函数来设置列表。

   private val callback : DiffUtil.ItemCallback<Item> = object: DiffUtil.ItemCallback<Item>() {
   
      override fun areItemsTheSame(oldItem: Item, newItem: Item) =
        oldItem.id == newItem.id
   
      override fun areContentsTheSame(oldItem: Item, newItem: Item) =
        oldItem == newItem
    }
   

4. 现在，对列表进行任何更改（插入/更新/删除）后，只需从片段/活动中调用此setData(list)即可。

   mAdapter.setData(list)

容易，对吧？

Answer 8

向现有数据添加新数据的最佳和最酷的方法是

 ArrayList<String> newItems = new ArrayList<String>();
 newItems = getList();
 int oldListItemscount = alcontainerDetails.size();
 alcontainerDetails.addAll(newItems);           
 recyclerview.getAdapter().notifyItemChanged(oldListItemscount+1, al_containerDetails);

Answer 9

我以不同的方式解决了同样的问题.我没有从后台线程等待它的数据,所以从一个emty列表开始.

        mAdapter = new ModelAdapter(getContext(),new ArrayList<Model>());
   // then when i get data

        mAdapter.update(response.getModelList());
  //  and update is in my adapter

        public void update(ArrayList<Model> modelList){
            adapterModelList.clear(); 
            for (Product model: modelList) {
                adapterModelList.add(model); 
            }
           mAdapter.notifyDataSetChanged();
        }

而已.