将项目值保存在Recycler View对象Android中

Question

I am working in recycler view where I have increment and decrement buttons. My condition is that maximum I can't add 10 and minimum 0. When I am clicking on increment button of 1st row item in recycler view it is adding 1, but when I am clicking on 2nd row item in recycler view it is affecting first item of list as well. Lets say item1 becomes 1 plus.

when I am doing any increment and decrement, it should not affect other row items in RecyclerView.

int counter = 0;

@Override
public void onBindViewHolder(final RecyclerView.ViewHolder  holder,final int position) {
    final ParseObject parseObject = arrayList.get(position);
    boolean like = true, dislike = true;
    if (holder instanceof MemberViewHolder) {
        if (arrayList.size() > 0) {
            ((MemberViewHolder) holder).txtIncrement.setOnClickListener(new TextView.OnClickListener() {
                @Override
                public void onClick(View view) {
                            counter += 1;
                            ((MemberViewHolder) holder).txtCounter.setText(counter+"");
                    }
            });
            ((MemberViewHolder) holder).txtDecrement.setOnClickListener(new TextView.OnClickListener() {
                @Override
                public void onClick(View view) {

                    if(counter == 0){

                    }else{
                        counter -= 1;
                        ((MemberViewHolder) holder).txtCounter.setText(counter+"");
                    }
                }
         });
     }
 }

When decrementing from item 1, it is decrementing value in row item2 as well. I want to keep the values per item.

Answer 1

you are getting trouble because off global variable counter. Instead of counter use private HashMap<Integer,Integer>counterMap=new HashMap<>(); private int counter=0; private HashMap<Integer,Integer>counterMap=new HashMap<>(); private int counter=0;

and your onclickeListener method will be like this

((MemberViewHolder) holder).txtIncrement.setOnClickListener(new TextView.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(counterMap.containsKey(position)) 
            counter =counterMap.get(position);
            else counter=0
            counter++;
            counterMap.put(position,counter)

            ((MemberViewHolder) holder).txtCounter.setText(counter+"");

        }
    });

Answer 2

I recommend to use a map for this.

private Map<Integer, Integer> countOfItems = new HashMap<>();

The key is the position of the item in your adapter. The value is the count of items for that position.

So inside your onBindViewHolder() you have to do some changes:

For incrementing:

int currentCount = countOfItems.get(position);
currentCount++;
countOfItems.put(position, currentCount);

For decrementing:

int currentCount = countOfItems.get(position);
if(currentCount > 0) {
  currentCount--;
  countOfItems.put(position, currentCount);
}

Initialize your map with count 0 for each item in the contructor of your adapter.

for(int i = 0; i < arrayList.size(); i++) {
  countOfItems.put(i, 0)
}

Answer 3

Here is how I did it:

First create a member variable of type int[]

private int[] counter = new int[10];

Here i have given the array a default size of 10 .

Important: This will crash your app if you try to increment item above index 10. To avoid that you need to give it the size of your arrayList when you populate the arrayList (possible in the adapter constructor).

Now in your onBindViewHolder() :

((MemberViewHolder) holder).txtIncrement.setOnClickListener(new TextView.OnClickListener() {
        @Override
        public void onClick(View view) {

                    counter[position] += 1;
                    ((MemberViewHolder) holder).txtCounter.setText(counter[position]+"");

        }
    });
    ((MemberViewHolder) holder).txtDecrement.setOnClickListener(new TextView.OnClickListener() {
        @Override
        public void onClick(View view) {

            if(counter[position] == 0){

            }else{
                counter[position] -= 1;
                ((MemberViewHolder) holder).txtCounter.setText(counter[position]+"");
            }
        }
    });                                                   
    ((MemberViewHolder) holder).txtCounter.setText(counter[position]+"");

Hope this helps!