在 RecyclerView Adapter 中处理 Spinner 的最佳实践是什么？
这是我的 RecyclerView 适配器:
public class CartAdapter extends BaseAdapter<Object> {
public CartAdapter(AbstractBaseActivity activity) {
super(activity);
}
public static final int TYPE_PRODOTTO = 1;
public static final int TYPE_SCONTO = 2;
@Override
public int getItemViewType(int position) {
if (items.get(position) instanceof Article)
return TYPE_PRODOTTO;
else
return TYPE_SCONTO;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View rowView = LayoutInflater.from(parent.getContext()).inflate(viewType == TYPE_PRODOTTO ? R.layout.item_cart : R.layout.item_cart_sconto, parent, false);
return new ViewHolder(rowView);
}
@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
final ViewHolder viewHolder = (ViewHolder) holder;
final Object object = items.get(position);
if (object instanceof Article) {
viewHolder.getBinding().setVariable(BR.article, object);
viewHolder.getBinding().executePendingBindings();
assert viewHolder.quantitySpinner != null;
assert viewHolder.cartoneQuantity != null;
assert viewHolder.cartoneValue != null;
CartSpinnerAdapter adapter = (CartSpinnerAdapter) viewHolder.quantitySpinner.getAdapter();
adapter.clear();
adapter.setCount(((Article) object).getQuantityAvailable());
adapter.notifyDataSetChanged();
viewHolder.quantitySpinner.setSelection(((Article) object).getQuantity() - 1); //In teoria qui la quantità non deve mai essere zero
viewHolder.cartoneQuantity.setVisibility(position % 2 == 1 ? View.GONE : View.VISIBLE); //Controllo da togliere in futuro
viewHolder.cartoneValue.setVisibility(position % 2 == 1 ? View.GONE : View.VISIBLE); //Controllo da togliere in futuro
}
final PopupMenu popup = new PopupMenu(getContext(), viewHolder.deleteMenu);
MenuInflater inflater = popup.getMenuInflater();
inflater.inflate(R.menu.delete_menu, popup.getMenu());
viewHolder.deleteMenu.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
popup.show();
}
});
popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
@Override
public boolean onMenuItemClick(MenuItem item) {
if (item.getItemId() == R.id.action_delete) {
removeData(holder.getAdapterPosition());
((CartActivity) activity).checkIfEmpty();
}
return true;
}
});
}
public class ViewHolder extends RecyclerView.ViewHolder {
@BindView(R.id.item)
View item;
@Nullable
@BindView(R.id.cart_image)
ImageView cartImage;
@BindView(R.id.delete_menu)
ImageView deleteMenu;
@Nullable
@BindView(R.id.product_cartone_quantity)
TextView cartoneQuantity;
@Nullable
@BindView(R.id.product_cartone_value)
TextView cartoneValue;
@Nullable
@BindView(R.id.quantity_spinner)
AppCompatSpinner quantitySpinner;
private ViewDataBinding binding;
public ViewHolder(View itemView) {
super(itemView);
ButterKnife.bind(this, itemView);
binding = DataBindingUtil.bind(itemView);
if (quantitySpinner != null)
quantitySpinner.setAdapter(new CartSpinnerAdapter(itemView.getContext(), R.layout.support_simple_spinner_dropdown_item));
}
public ViewDataBinding getBinding() {
return binding;
}
}
}
这是我的
Spinner 适配器:public class CartSpinnerAdapter extends ArrayAdapter<String> {
LayoutInflater inflater;
int count;
public CartSpinnerAdapter(Context context, int resource) {
super(context, resource);
inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public CartSpinnerAdapter(Context context, int resource, int count) {
super(context, resource);
this.count = count;
inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void setCount(int count) {
this.count = count;
}
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
return getStandardView(position, parent, true);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
return getStandardView(position, parent, false);
}
@Override
public int getCount() {
return count;
}
private View getStandardView(int position, ViewGroup parent, boolean dropdown) {
View row = inflater.inflate(R.layout.support_simple_spinner_dropdown_item, parent, false);
TextView title = (TextView) row.findViewById(android.R.id.text1);
title.setText(String.valueOf(position + 1));
if (dropdown)
title.setMinWidth(Utils.dpToPx(getContext(), 64));
else
title.setAlpha(0.5f);
return row;
}
}
这样，当我滚动
RecyclerView 时，我遇到了滞后。如果我删除这些行，一切正常:
CartSpinnerAdapter adapter = (CartSpinnerAdapter) viewHolder.quantitySpinner.getAdapter();
adapter.clear();
adapter.setCount(((Article) object).getQuantityAvailable());
adapter.notifyDataSetChanged();
所以问题是我处理
Spinner 适配器的方式，我该如何处理？提前致谢。
最佳答案
短
为了提高性能，
背景
当使用适配器进行滚动时，最重要的是要确保我们 不要 分配新对象(或尽可能减少它)。
带有 Adapter 的 RecyclerView 的全部目的是确保我们回收我们的对象，以便滚动期间所需的工作最少。
由于分配内存非常“昂贵”，为了提高滚动性能，首先要寻找的是 onBindViewHolder 期间的分配。所有分配(如果有)都应在 onCreateViewHolder 中进行。
一旦所有分配都被清除，如果我们仍然有滞后，是时候进行一些微改进了。这些包括提高代码质量、重用逻辑结果等。
怎么办？
1) 从 onBindViewHolder 移除分配
在以下代码中:
final PopupMenu popup = new PopupMenu(getContext(), viewHolder.deleteMenu);
MenuInflater inflater = popup.getMenuInflater();
inflater.inflate(R.menu.delete_menu, popup.getMenu());
viewHolder.deleteMenu.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
popup.show();
}
});
popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
@Override
public boolean onMenuItemClick(MenuItem item) {
if (item.getItemId() == R.id.action_delete) {
removeData(holder.getAdapterPosition());
((CartActivity) activity).checkIfEmpty();
}
return true;
}
});
您目前有 3 个直接分配( new )和一些间接分配( inflate )。更改此代码，以便所有分配都在 onCreateViewHolder 中。例如:
在 onCreateViewHolder 中做这样的分配:
// Allocate Listener only ONCE per recycled view
viewHolder.deleteMenu.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Get needed data from the view TAG, we will set it later
final int itemPosition = (Integer)view.getTag();
// Do work only when needed - when user clicked the button
final PopupMenu popup = new PopupMenu(getContext(), viewHolder.deleteMenu);
MenuInflater inflater = popup.getMenuInflater();
inflater.inflate(R.menu.delete_menu, popup.getMenu());
popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
@Override
public boolean onMenuItemClick(MenuItem item) {
// Do logic using itemPosition etc
return true;
}
});
popup.show();
}
});
在 onBindViewHolder 绑定(bind)相关数据，如下所示:
viewHolder.deleteMenu.setTag(holder.getAdapterPosition());
2) 重用 LayoutInflater ，而不是每次都得到一个新的。
在以下代码中:
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View rowView = LayoutInflater.from(parent.getContext()).inflate(viewType == TYPE_PRODOTTO ? R.layout.item_cart : R.layout.item_cart_sconto, parent, false);
return new ViewHolder(rowView);
}
你每次都会得到一个新的 LayoutInflater。这是一种浪费。最好在 Adapter 构造函数中获取一个并将其保存为成员。
3)最小化 onBindViewHolder 实现中的重复工作
例如，在以下代码中:
viewHolder.cartoneQuantity.setVisibility(position % 2 == 1 ? View.GONE : View.VISIBLE); //Controllo da togliere in futuro
viewHolder.cartoneValue.setVisibility(position % 2 == 1 ? View.GONE : View.VISIBLE); //Controllo da togliere in futuro
您正在计算相同的逻辑两次。最好计算一次并重用结果:
int cartoneVisibility = position % 2 == 1 ? View.GONE : View.VISIBLE;
viewHolder.cartoneQuantity.setVisibility(cartoneVisibility); //Controllo da togliere in futuro
viewHolder.cartoneValue.setVisibility(cartoneVisibility); //Controllo da togliere in futuro
4) Spinner Adapter 也应该回收 View
在
CartSpinnerAdapter.getView() 中，您也在分配内存。它发生了(每次 * 列表项 * 计数)——这是很多分配。请改用 convertView。看看这个教程 dzone.com/articles/android-listview-optimizations关于android - 如何在 Recyclerview 中使用 Spinner？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/38762010/