当用户从上下文菜单中选择选项时，回收器视图无法获得正确的位置来执行任务

Question

我的应用无法获得正确的位置来执行用户从上下文菜单中选择的任务。

主活动.java

public class Main3Activity extends AppCompatActivity {
private RecyclerView recyclerView;
private List<foodmodel> result;
private foodadapter adapter;
private FirebaseDatabase database;
private DatabaseReference ref;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main3);
database = FirebaseDatabase.getInstance();
ref = database.getReference("Food");
result = new ArrayList<>();
recyclerView = (RecyclerView)findViewById(R.id.food_list);
recyclerView.setHasFixedSize(true);
LinearLayoutManager lim = new LinearLayoutManager(this);
lim.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(lim);

adapter = new foodadapter(result);
recyclerView.setAdapter(adapter);
updateList();
}
@Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId())
{
case 0:
removeFood(item.getItemId());
break;
case 1:
changeFood(item.getItemId());
break;
}
return super.onContextItemSelected(item);
}

private void updateList()
{
ref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
result.add(dataSnapshot.getValue(foodmodel.class));
adapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
foodmodel food = dataSnapshot.getValue(foodmodel.class);
int index = getItemIndex(food);
result.set(index,food);
adapter.notifyItemChanged(index);
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
foodmodel food = dataSnapshot.getValue(foodmodel.class);
int index = getItemIndex(food);
result.remove(index);
adapter.notifyItemRemoved(index);
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private int getItemIndex(foodmodel food){
int index = -1;
for(int i = 0; i < result.size();i++)
{
if (result.get(i).key.equals(food.key))
{
index = i;
break;
}
}
return index;
}

private void removeFood(int pos){
foodmodel food = result.get(pos);
String key = food.getKey();
food.u_time="remove";
Map<String,Object> foodValue = food.toMap();
Map<String,Object> newFood = new HashMap<>();
newFood.put(key,foodValue);
ref.updateChildren(newFood);
}
private void changeFood(int pos){
foodmodel food = result.get(pos);
food.u_time="change";
Map<String,Object> foodValue = food.toMap();
Map<String,Object> newFood = new HashMap<>();
newFood.put(food.key,foodValue);
ref.updateChildren(newFood);
}
}

食品适配器.java

public class foodadapter extends RecyclerView.Adapter<foodadapter.foodviewholder> {
private List<foodmodel>list;
public foodadapter(List<foodmodel> list) {
this.list = list;
}
@Override
public foodviewholder onCreateViewHolder(ViewGroup parent, int viewType) {
return new foodviewholder(LayoutInflater.from(parent.getContext()).inflate(R.layout.view_item,parent,false));
}
@Override
public void onBindViewHolder(foodviewholder holder, int position) {
foodmodel food = list.get(position);
holder.txtname.setText(food.u_food);
holder.txtdate.setText(food.u_date);
holder.txttime.setText(food.u_time);
}
@Override
public int getItemCount() {
return list.size();
}
public class foodviewholder extends RecyclerView.ViewHolder implements OnCreateContextMenuListener {
TextView txtname,txtdate,txttime;
Button btn;
public foodviewholder(View itemView) {
super(itemView);
txtname = (TextView)itemView.findViewById(R.id.text_food);
txtdate = (TextView)itemView.findViewById(R.id.text_date);
txttime = (TextView)itemView.findViewById(R.id.text_time);
btn = (Button)itemView.findViewById(R.id.btntest);
itemView.setOnCreateContextMenuListener(this);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
menu.add(0, 0, 0, "Delete");
menu.add(0, 1, 0, "Change");
}
}
}

福模特.java

public class foodmodel {
String u_food,u_date,u_time,key;
public foodmodel(){}
public foodmodel(String  u_food,String u_date,String u_time, String key) {
this.u_food = u_food;
this.u_date = u_date;
this.u_time = u_time;
this.key = key;
}
public Map<String,Object> toMap(){
HashMap<String,Object> result = new HashMap<>();
result.put("u_food",u_food);
result.put("u_time",u_time);
result.put("u_date",u_date);
result.put("key",key);
return  result;
}
public String getU_food() {
return u_food;
}
public void setU_food(String u_food) {
this.u_food = u_food;
}
public String getU_date() {
return u_date;
}
public void setU_date(String u_date) {
this.u_date = u_date;
}
public String getU_time() {
return u_time;
}
public void setU_time(String u_time) {
this.u_time = u_time;
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
}

应用程序的流程应该像

1. 显示从 Firebase 检索的回收器视图
2. 用户从列表中选择项目
3. 弹出上下文菜单
4. 用户选择删除或更改
5. 如果删除，则食物的u_time变为"删除">
6. 如果改变，那么食物u_time就变成了"变化">

从 1-4 的步骤工作正常。 但在那之后，应用程序无法获得正确执行任务的位置。

例如，如果用户在第三项上选择"删除"，但第一项将被更改。之后，用户在第四个项目上选择"更改"，第二个项目更改。我的代码有问题吗？

Answer 1

像 这样替换你的代码：

主活动.java

public class Main3Activity extends AppCompatActivity {
private RecyclerView recyclerView;
private List<foodmodel> result;
private foodadapter adapter;
private FirebaseDatabase database;
private DatabaseReference ref;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main3);
database = FirebaseDatabase.getInstance();
ref = database.getReference("Food");
result = new ArrayList<>();
recyclerView = (RecyclerView)findViewById(R.id.food_list);
recyclerView.setHasFixedSize(true);
LinearLayoutManager lim = new LinearLayoutManager(this);
lim.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(lim);

adapter = new foodadapter(result);
recyclerView.setAdapter(adapter);
updateList();
}
@Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId())
{
case 0:
if(adapter.curPos>-1){
removeFood(adapter.curPos);
}
break;
case 1:
if(adapter.curPos>-1){
changeFood(adapter.curPos);
}
break;
}
return super.onContextItemSelected(item);
}

private void updateList()
{
ref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
result.add(dataSnapshot.getValue(foodmodel.class));
adapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
foodmodel food = dataSnapshot.getValue(foodmodel.class);
int index = getItemIndex(food);
result.set(index,food);
adapter.notifyItemChanged(index);
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
foodmodel food = dataSnapshot.getValue(foodmodel.class);
int index = getItemIndex(food);
result.remove(index);
adapter.notifyItemRemoved(index);
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private int getItemIndex(foodmodel food){
int index = -1;
for(int i = 0; i < result.size();i++)
{
if (result.get(i).key.equals(food.key))
{
index = i;
break;
}
}
return index;
}

private void removeFood(int pos){
foodmodel food = result.get(pos);
String key = food.getKey();
food.u_time="remove";
Map<String,Object> foodValue = food.toMap();
Map<String,Object> newFood = new HashMap<>();
newFood.put(key,foodValue);
ref.updateChildren(newFood);
}
private void changeFood(int pos){
foodmodel food = result.get(pos);
food.u_time="change";
Map<String,Object> foodValue = food.toMap();
Map<String,Object> newFood = new HashMap<>();
newFood.put(food.key,foodValue);
ref.updateChildren(newFood);
}
}

食品适配器.java

public class foodadapter extends RecyclerView.Adapter<foodadapter.foodviewholder> {
private List<foodmodel>list;
public int curPos=-1;
public foodadapter(List<foodmodel> list) {
this.list = list;
}
@Override
public foodviewholder onCreateViewHolder(ViewGroup parent, int viewType) {
return new foodviewholder(LayoutInflater.from(parent.getContext()).inflate(R.layout.view_item,parent,false));
}
@Override
public void onBindViewHolder(foodviewholder holder, int position) {
foodmodel food = list.get(position);
holder.txtname.setText(food.u_food);
holder.txtdate.setText(food.u_date);
holder.txttime.setText(food.u_time);
}
@Override
public int getItemCount() {
return list.size();
}
public class foodviewholder extends RecyclerView.ViewHolder implements OnCreateContextMenuListener {
TextView txtname,txtdate,txttime;
Button btn;
public foodviewholder(View itemView) {
super(itemView);
txtname = (TextView)itemView.findViewById(R.id.text_food);
txtdate = (TextView)itemView.findViewById(R.id.text_date);
txttime = (TextView)itemView.findViewById(R.id.text_time);
btn = (Button)itemView.findViewById(R.id.btntest);
itemView.setOnCreateContextMenuListener(this);
itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
curPos=getAdapterPosition();
}});
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
menu.add(0, 0, 0, "Delete");
menu.add(0, 1, 0, "Change");
}
}
}