我正在开发一个电子商务应用程序，以下一些在线订单。在我的Recyclerview中有一些产品，它们是在上一个活动中添加的。在这里，我在Recyclerview中用产品名称，数量，价格等详细信息填充了添加的产品。有一些按钮可以增加/减少每种产品的数量，还有一个按钮也可以删除该项目。
在Recyclerview布局的底部，还有另一个textview用于显示总计。当我在处理RecyclerViewAdapter类中的按钮时，当用户更新数量或删除项目时，我必须更新总计。我尝试了这里已经提到的一些解决方案，但是该应用程序在随机单击按钮时崩溃。请提供解决方案或更好的方法。
这是我的适配器类：
public class InvoiceRecyclerViewAdapter extends RecyclerView.Adapter<InvoiceRecyclerViewAdapter.ViewHolder> {
private static final String TAG = "RecylerViewAdapter";
List<Products> addedProductsList;
Context mContext;
public InvoiceRecyclerViewAdapter(Context mContext,List<Products> addedProductsList)
{
this.mContext=mContext;
this.addedProductsList=addedProductsList;
}
public InvoiceRecyclerViewAdapter(Context mContext)
{
this.mContext=mContext;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_invoice,parent,false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, final int position) {
holder.item_qty.setText("1");
holder.itemname.setText(addedProductsList.get(position).getName());
holder.itemprice.setText("Rs "+addedProductsList.get(position).getPrice());
holder.itemdiscount.setText("Rs "+calculate_dis(position));
holder.itemtotal.setText("Rs "+calculate_total(position));
holder.button_inc.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int qty = addedProductsList.get(position).getQty();
qty++;
addedProductsList.get(position).setQty(qty);
holder.item_qty.setText(""+qty);
holder.itemdiscount.setText("Rs "+calculate_dis(position));
holder.itemtotal.setText("Rs "+calculate_total(position));
UpdateTotal();
}
});
holder.button_dec.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int qty = addedProductsList.get(position).getQty();
qty--;
if(qty>0){
addedProductsList.get(position).setQty(qty);
holder.item_qty.setText(""+qty);
holder.itemdiscount.setText("Rs"+calculate_dis(position));
holder.itemtotal.setText("Rs"+calculate_total(position));
UpdateTotal();
}
}
});
holder.button_cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
addedProductsList.get(position).setAddedTocart(false);
//notifyDataSetChanged();
addedProductsList.remove(position);
notifyItemRemoved(position);
UpdateTotal();
}
});
}
@Override
public int getItemCount() {
return addedProductsList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder{
TextView itemname,itemtotal,itemprice,itemdiscount,item_qty;
Button button_cancel,button_inc,button_dec;
ConstraintLayout parent_layout;
public ViewHolder(View itemView) {
super(itemView);
itemname = itemView.findViewById(R.id.textView_item_name);
itemprice = itemView.findViewById(R.id.textView_item_price);
itemdiscount = itemView.findViewById(R.id.textView_item_discount);
itemtotal = itemView.findViewById(R.id.textView_item_total);
button_cancel = itemView.findViewById(R.id.button_cancel);
button_inc=itemView.findViewById(R.id.button_inc);
button_dec=itemView.findViewById(R.id.button_dec);
item_qty = itemView.findViewById(R.id.textView_qty);
parent_layout = itemView.findViewById(R.id.invoice_parent_layout);
}
}
private float calculate_dis(int pos){
float dis = 0;
if(addedProductsList.get(pos).isPrice_g_enabled()){
int qty=addedProductsList.get(pos).getQty();
dis = Float.parseFloat(addedProductsList.get(pos).getPrice())-Float.parseFloat(addedProductsList.get(pos).getPrice_g());
dis = qty*dis;
}
return dis;
}
private float calculate_total(int pos){
int qty=addedProductsList.get(pos).getQty();
float price,total;
if(addedProductsList.get(pos).isPrice_g_enabled()){
price = Float.parseFloat(addedProductsList.get(pos).getPrice_g());
}
else{
price= Float.parseFloat(addedProductsList.get(pos).getPrice());
}
total = price*qty;
return total;
}
private void UpdateTotal(){
TextView txtView =((EditQuantity)mContext).findViewById(R.id.textView_total);
float total=0,price=0;
int qty=0;
for(int i=0;i<addedProductsList.size();i++){
if(addedProductsList.get(i).isAddedTocart()) {
qty = addedProductsList.get(i).getQty();
if(addedProductsList.get(i).isPrice_g_enabled()){
price = Float.parseFloat(addedProductsList.get(i).getPrice_g());
}
else{
price= Float.parseFloat(addedProductsList.get(i).getPrice());
}
}
total=total+(qty*price);
}
txtView.setText("Rs "+total);
}
}
这是“主要活动”部分：
public class EditQuantity extends AppCompatActivity {
ArrayList<Products> products_list;
ArrayList<Products> cart_productslist= new ArrayList<>();
Products added_product;
FloatingActionButton fab_next;
TextView total_textview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit_quantity);
products_list = getIntent().getParcelableArrayListExtra("products");
Products products;
for(int i=0;i<products_list.size();i++){
products = products_list.get(i);
if(products.isAddedTocart()){
added_product = new Products(products.getName(),products.getPrice(),products.getPrice_g(),products.getImage(),1,true,products.isPrice_g_enabled());
cart_productslist.add(added_product);
}
}
Toolbar toolbar = findViewById(R.id.toolbar_invoice);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("Cart");
total_textview = findViewById(R.id.textView_total);
total_textview.setText("Rs "+CalTotal());
fab_next = findViewById(R.id.fab_next);
fab_next.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
InitRecylerView();
}
@Override
public void onBackPressed() {
}
private void InitRecylerView() {
RecyclerView recyclerView = findViewById(R.id.invoice_recyclerview);
InvoiceRecyclerViewAdapter adapter = new InvoiceRecyclerViewAdapter(
this ,cart_productslist);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
}
public float CalTotal(){
float total=0;
float i_total,price;
for(int i=0;i<cart_productslist.size();i++){
if(cart_productslist.get(i).isAddedTocart()) {
int qty = cart_productslist.get(i).getQty();
if(cart_productslist.get(i).isPrice_g_enabled()){
price = Float.parseFloat(cart_productslist.get(i).getPrice_g());
}
else{
price= Float.parseFloat(cart_productslist.get(i).getPrice());
}
i_total = price * qty;
total = total + i_total;
}
}
return total;
}
答案 0 :(得分：2)
我建议您通过一个侦听器，移动您的onClickListeners并删除for循环。
所以，一步一步
在您的适配器类中声明一个接口
SELECT b1.*
FROM batteries b1
INNER JOIN
(
SELECT BatteryID, MAX(Date) AS max_date
FROM batteries
WHERE type = 'NiMh AA'
GROUP BY BatteryID
) b2
ON b1.BatteryID = b2.BatteryID AND b1.Date = b2.max_date
WHERE
b1.type = 'NiMh AA';
接下来，将一个私有的OnQuantityChangeListener添加到您的适配器类，并更改构造函数以在创建时添加一个：
public interface OnQuantityChangeListener {
void onQuantityChange( float change );
}
在onBindViewHolder方法中设置OnClickListeners对性能不利，因为这意味着您必须在视图弹出到屏幕上时添加它们。而是在onCreateViewHolder方法中设置它们，那样您将对其进行回收。要获取当前项目，可以使用 getAdapterPosition（）方法。
因此，在 onCreateViewHolder 方法中设置侦听器：
private OnQuantityChangeListener mListener;
public InvoiceRecyclerViewAdapter(Context mContext,List<Products> addedProductsList, OnQuantityChangeListener listener) {
this.mContext=mContext;
this.addedProductsList=addedProductsList;
mListener = listener;
}
public InvoiceRecyclerViewAdapter(Context mContext, OnQuantityChangeListener listener)
{
this.mContext=mContext;
mListener = listener;
}
此时请记住要从 onBindViewHolder 方法中删除OnClickListeners。
完成此操作后，转到您的活动并添加私人总计：
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_invoice,parent,false);
ViewHolder viewHolder = new ViewHolder(view);
viewHolder.button_inc.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Products product = addedProductsList.get(getAdapterPosition());
product.setQty( product.getQty() + 1 );
float difference = product.isPrice_g_enabled() ? Float.parseFloat(product.getPrice_g()) : Float.parseFloat(product.getPrice());
mListener.onQuantityChange( difference );
notifyItemChanged( getAdapterPosition ):// This will call onBindViewAdapter again and change all your strings for you
}
});
viewHolder.button_dec.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Products product = addedProductsList.get(getAdapterPosition());
if( product.getQty() == 0 )// Can't remove an item if it's already at 0
return;
product.setQty( product.getQty() - 1 );
float difference = product.isPrice_g_enabled() ? Float.parseFloat(product.getPrice_g()) : Float.parseFloat(product.getPrice());
mListener.onQuantityChange( -difference );
notifyItemChanged( getAdapterPosition ):// This will call onBindViewAdapter again and change all your strings for you
}
});
viewHolder.button_cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Products product = addedProductsList.get(getAdapterPosition());
float difference = product.isPrice_g_enabled() ? Float.parseFloat(product.getPrice_g()) : Float.parseFloat(product.getPrice());
mListener.onQuantityChange( -difference * product.getQty() );
product.setQty( 0 );
notifyItemChanged( getAdapterPosition ):// This will call onBindViewAdapter again and change all your strings for you
// You decide at this point if you want to remove the item altogether or just show 0
}
});
return viewHolder;
}
并像这样编辑适配器的创建：
private float total = 0;
然后就可以了。记住要一次计算您的活动中的第一个总数（这里不要转义for循环），然后确保保存实例状态。
希望这会有所帮助！