为什么 EditText 中的输入值在 RecyclerView 中滚动时会交换其位置？

【问题标题】：Why does the input value in EditText swaps its position while scrolling in a RecyclerView?为什么 EditText 中的输入值在 RecyclerView 中滚动时会交换其位置？
【发布时间】：2015-12-06 06:33:14
【问题描述】：

在 EditText 中输入输入后，如果快速向上或向下滚动，则输入值会在 RecyclerView 的另一个 EditText 中交换其位置。
滚动数据之前是在第一个 EditText 中。
上下滚动后，第一个 EditText 的值将其位置更改为第四个，并且交换是随机的。有什么办法可以稳定数据。

Here is a sample screenshot

这是模型类：

public class Product {    
    public int pId;    
    public String pName;    
    public double unit_price;    
    public double discount;    
}

这是适配器类：

public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ProductListHolder> {
Context context;
List<Product> productList;

public ProductAdapter(Context c, List<Product> lp){
    this.context = c;
    this.productList = lp;
}

public class ProductListHolder extends RecyclerView.ViewHolder{
    TextView tvName;
    TextView tvPrice;
    TextView tvDiscount;
    TextView tvTotal;
    EditText etQuantity;
    public ProductListHolder(View itemView) {
        super(itemView);
        tvName = (TextView) itemView.findViewById(R.id.tvName);
        tvPrice = (TextView) itemView.findViewById(R.id.tvPrice);
        tvDiscount = (TextView) itemView.findViewById(R.id.tvDiscount);
        tvTotal = (TextView) itemView.findViewById(R.id.tvTotal);
        etQuantity = (EditText) itemView.findViewById(R.id.etQuantity);
    }
}

@Override
public ProductListHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
    View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.single_row, viewGroup, false);
    ProductListHolder ph = new ProductListHolder(v);
    return  ph;
}

@Override
public void onBindViewHolder(final ProductListHolder productListHolder, final int i) {
    productListHolder.tvName.setText(productList.get(i).pName);
    productListHolder.tvPrice.setText(String.valueOf(productList.get(i).unit_price));
    productListHolder.tvDiscount.setText(String.valueOf(productList.get(i).discount));

    productListHolder.etQuantity.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            if (!s.toString().equals("")){
                double totalPrice = (productList.get(i).unit_price-productList.get(i).discount)* (Double.valueOf(s.toString()));
                productListHolder.tvTotal.setText(String.valueOf(totalPrice));
            }
        }

        @Override
        public void afterTextChanged(Editable s) {

        }
    });
}

@Override
public int getItemCount() {
    return productList.size();
}

}

这里是 MainActivity：

public class MainActivity extends AppCompatActivity {

List<Product> productList;
RecyclerView recyclerView;
RecyclerView.Adapter mAdapter;

String[] names = {"A", "B", "C","D"};
double[] prices = {1000, 2000, 3000, 100};
double[] discounts = {10, 20, 30, 2};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initRecyclerView(); // Initializing Recycler View
    new MyTask().execute();
}

public void initRecyclerView(){
    recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);
    recyclerView.setLayoutManager(new LinearLayoutManager(MainActivity.this));
}

private class MyTask extends AsyncTask<Void, Void, List<Product>> {

    @Override
    protected List<Product> doInBackground(Void... params) {
        int sz = 24;
        productList = new ArrayList<Product>();
        for(int i=0; i<sz; i++){
            Product p = new Product();
            p.pId = i%4;
            p.pName = names[i%4];
            p.unit_price = prices[i%4];
            p.discount = discounts[i%4];
            productList.add(p);
        }

        return productList;
    }

    @Override
    protected void onPostExecute(List<Product> products) {
        super.onPostExecute(products);
        mAdapter = new ProductAdapter(MainActivity.this, productList);
        recyclerView.setAdapter(mAdapter);
    }
  }    
}

【问题讨论】：

    标签： android android-edittext android-recyclerview android-viewholder


    【解决方案1】：

    我认为你做得很好。但是您解决的问题可以通过非常简单的方式解决。你只需要实现一个 Overridden 方法：

    public int getItemViewType(int position) { 返回 super.getItemViewType(位置); }

    代替-

    return super.getItemViewType(position);

    刚回来-

    返回位置；

    我认为您的所有问题都会以简单的方式解决。这是我稍微修改的适配器类：

    public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ProductListHolder> {

Context context;
List<Product> productList;


public ProductAdapter(Context c, List<Product> lp) {
    this.context = c;
    this.productList = lp;
}

public class ProductListHolder extends RecyclerView.ViewHolder {
    TextView tvName;
    TextView tvPrice;
    TextView tvDiscount;
    TextView tvTotal;
    EditText etQuantity;

    public ProductListHolder(View itemView) {
        super(itemView);
        tvName = (TextView) itemView.findViewById(R.id.tvName);
        tvPrice = (TextView) itemView.findViewById(R.id.tvPrice);
        tvDiscount = (TextView) itemView.findViewById(R.id.tvDiscount);
        tvTotal = (TextView) itemView.findViewById(R.id.tvTotal);
        etQuantity = (EditText) itemView.findViewById(R.id.etQuantity);
    }
}

@Override
public ProductListHolder onCreateViewHolder(ViewGroup viewGroup, final int i) {
    View v = LayoutInflater.from(context).inflate(R.layout.single_row, viewGroup, false);
    ProductListHolder ph = new ProductListHolder(v);
    return ph;
}

@Override
public void onBindViewHolder(final ProductListHolder productListHolder, final int i) {

    productListHolder.tvName.setText(productList.get(i).pName);
    productListHolder.tvPrice.setText(String.valueOf(productList.get(i).unit_price));
    productListHolder.tvDiscount.setText(String.valueOf(productList.get(i).discount));

    productListHolder.etQuantity.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            productListHolder.tvTotal.setText(s.toString());
        }

        @Override
        public void afterTextChanged(Editable s) {
        }
    });

}

@Override
public int getItemCount() {
    return productList.size();
}

@Override
public int getItemViewType(int position) {
    return position;
}    
}

    【讨论】：

    • 它对我有用。但这怎么能解决问题呢？似乎被覆盖的 getItemViewType(position) 以错误的方式写入，因此不应该被覆盖，而是返回另一个值。
    【解决方案2】：

    我已经解决了这个问题。

    问题是我在 onBindViewHolder 中添加了 addTextChangedListener。所以 EditText 中的值总是混乱的，因为当焦点转移时，另一个 addTextChangedListener 被注册了。所以我所做的是，我实现了另一个名为 CustomEtListener 的自定义类并实现了 TextWatcher。所以现在我在 onCreateViewHolder 中为每个 EditText 注册了自定义监听器。并采用 array 字符串来存储编辑文本的值。数组的大小是 RecyclerView 中的项目数。 updatePosition 方法用于获取焦点项目的位置。然后 onTextChanged 我只是将 editText 的值存储在数组中，并在 onBindViewHolder 中更新了该 EditText 的值。之后每次滚动时，EditText 的值都不会改变。

    这是我的适配器类。

    public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ProductListHolder> {
Context context;
List<Product> productList;
String[] etValArr;
double[] totalValue;

public ProductAdapter(Context c, List<Product> lp) {
    this.context = c;
    this.productList = lp;
    // Create a new array which size matches the number of Edit Texts
    etValArr = new String[productList.size()];
    // and an array for holding all the values of each edit text
    totalValue = new double[productList.size()];
}

public class ProductListHolder extends RecyclerView.ViewHolder {
    TextView tvName;
    TextView tvPrice;
    TextView tvDiscount;
    TextView tvTotal;
    EditText etQuantity;

    // Instance of a Custom edit text listener
    public CustomEtListener myCustomEditTextListener;

    public ProductListHolder(View itemView, CustomEtListener myLis) {
        super(itemView);
        tvName = (TextView) itemView.findViewById(R.id.tvName);
        tvPrice = (TextView) itemView.findViewById(R.id.tvPrice);
        tvDiscount = (TextView) itemView.findViewById(R.id.tvDiscount);
        tvTotal = (TextView) itemView.findViewById(R.id.tvTotal);
        etQuantity = (EditText) itemView.findViewById(R.id.etQuantity);
        // assign a new instance of addTextChangedListener for each item
        myCustomEditTextListener = myLis;
        etQuantity.addTextChangedListener(myCustomEditTextListener);
    }
}

@Override
public ProductListHolder onCreateViewHolder(ViewGroup viewGroup, final int i) {
    View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.single_row, viewGroup, false);
    ProductListHolder ph = new ProductListHolder(v, new CustomEtListener());
    return ph;
}

@Override
public void onBindViewHolder(final ProductListHolder productListHolder, int i) {
    productListHolder.tvName.setText(productList.get(i).pName);
    productListHolder.tvPrice.setText(String.valueOf(productList.get(i).unit_price));
    productListHolder.tvDiscount.setText(String.valueOf(productList.get(i).discount));

    // Update the position when focus changes
    productListHolder.myCustomEditTextListener.updatePosition(i);
    // Setting the values accordingly
    productListHolder.etQuantity.setText(etValArr[i]);
    productListHolder.tvTotal.setText(String.valueOf(totalValue[i]));

}

@Override
public int getItemCount() {
    return productList.size();
}

/**
 * Custom class which implements Text Watcher
 */
private class CustomEtListener implements TextWatcher {
    private int position;

    /**
     * Updates the position according to onBindViewHolder
     *
     * @param position - position of the focused item
     */
    public void updatePosition(int position) {
        this.position = position;
    }

    @Override
    public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
    }

    @Override
    public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
        // Change the value of array according to the position
        etValArr[position] = charSequence.toString();
        // Doing the calculation
        if (!etValArr[position].equals("")) {
            totalValue[position] = (productList.get(position).unit_price - productList.get(position).discount) * (Double.valueOf(etValArr[position]));

        } else {
            totalValue[position] = 0.00;
        }
    }

    @Override
    public void afterTextChanged(Editable editable) {
    }
}
}

    我还是有问题。我无法更新 Total 列的值。在我上下滚动之后，值就改变了。所以我必须实现一个回调侦听器来立即获取 Total 列的值。我现在有一个接口 TextCallBackListener，并在 Adapters ProductListHoldersClass 上实现了它。因此，每当调用 onTextChanged 时，它都会触发我的 updateText 方法来更改该行 Total 的值。看不懂的，问题里有截图。

    这里是TextCallBackListener接口。

    public interface TextCallBackListener {
      public void updateText(String val);
}

    这是我更改后的适配器类。

    public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ProductListHolder> {
Context context;
List<Product> productList;
String[] etValArr;
double[] totalValue;

public ProductAdapter(Context c, List<Product> lp) {
    this.context = c;
    this.productList = lp;
    // Create a new array which size matches the number of Edit Texts
    etValArr = new String[productList.size()];
    // and an array for holding all the values of each edit text
    totalValue = new double[productList.size()];
}


public class ProductListHolder extends RecyclerView.ViewHolder implements TextCallBackListener {
    TextView tvName;
    TextView tvPrice;
    TextView tvDiscount;
    TextView tvTotal;
    EditText etQuantity;

    // Instance of a Custom edit text listener
    public CustomEtListener myCustomEditTextListener;

    public ProductListHolder(View itemView, CustomEtListener myLis) {
        super(itemView);
        tvName = (TextView) itemView.findViewById(R.id.tvName);
        tvPrice = (TextView) itemView.findViewById(R.id.tvPrice);
        tvDiscount = (TextView) itemView.findViewById(R.id.tvDiscount);
        tvTotal = (TextView) itemView.findViewById(R.id.tvTotal);
        etQuantity = (EditText) itemView.findViewById(R.id.etQuantity);
        // assign a new instance of addTextChangedListener for each item
        myCustomEditTextListener = myLis;
        etQuantity.addTextChangedListener(myCustomEditTextListener);
    }

    @Override
    public void updateText(String val) {
        tvTotal.setText(val);
    }
}


@Override
public ProductListHolder onCreateViewHolder(ViewGroup viewGroup, final int i) {
    View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.single_row, viewGroup, false);
    ProductListHolder ph = new ProductListHolder(v, new CustomEtListener());
    return ph;
}

@Override
public void onBindViewHolder(final ProductListHolder productListHolder, int i) {
    productListHolder.tvName.setText(productList.get(i).pName);
    productListHolder.tvPrice.setText(String.valueOf(productList.get(i).unit_price));
    productListHolder.tvDiscount.setText(String.valueOf(productList.get(i).discount));

    // Update the position when focus changes
    productListHolder.myCustomEditTextListener.updatePosition(i, productListHolder);
    // Setting the values accordingly
    productListHolder.etQuantity.setText(etValArr[i]);
    //productListHolder.tvTotal.setText(String.valueOf(totalValue[i]));

}


@Override
public int getItemCount() {
    return productList.size();
}

/**
 * Custom class which implements Text Watcher
 */
private class CustomEtListener implements TextWatcher {
    private int position;
    TextCallBackListener textCallBackListener;

    /**
     * Updates the position according to onBindViewHolder
     *
     * @param position - position of the focused item
     * @param pa       - object of ProductListHolder Class
     */
    public void updatePosition(int position, ProductListHolder pa) {
        this.position = position;
        // assigning it to the instance of the CallBackListener
        textCallBackListener = (TextCallBackListener) pa;
    }

    @Override
    public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
    }

    @Override
    public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
        // Change the value of array according to the position
        etValArr[position] = charSequence.toString();
        // Doing the calculation
        if (!etValArr[position].equals("")) {
            totalValue[position] = (productList.get(position).unit_price - productList.get(position).discount) * (Double.valueOf(etValArr[position]));
            // triggering the callback function to update the total
            textCallBackListener.updateText(String.valueOf(totalValue[position]));
        } else {
            totalValue[position] = 0.00;
            textCallBackListener.updateText("0.00");
        }
    }

    @Override
    public void afterTextChanged(Editable editable) {

    }

}
}

    【讨论】：

    • viewholder 不能转换为 textCallBackListener ？
    【解决方案3】：

    您正在调用etQuantity.addTextChangedListener，但您永远不会删除侦听器，因此当视图持有者被回收（也就是用来显示另一个项目）时，它会添加另一个文本更改侦听器（所以它'将注册两个不同的文本更改侦听器）。

    最简单的解决方法可能是在onCreateViewHolder 中只调用一次addTextChangedListener 并使用getAdapterPosition 而不是i 来获取位置。

    【讨论】：

    • 它对我不起作用。您告诉我使用 getAdapterPostion() ，但这是在滚动期间更改焦点时动态更改的索引。
    【解决方案4】：

    简单修复：

    替换 mFieldAdapter.notifyDataSetChanged(); 为：

    for (int i = 0; i < mFieldAdapter.getItemCount(); i++) {
    // update each item itself
    mFieldAdapter.notifyItemChanged(i, fields.get(i));
}

    演示：https://youtu.be/4JpzuLggBV0

    【讨论】：

      【解决方案5】：

      以上所有代码都不适合我。我只使用HashMap 就找到了简单的解决方案。

      在RecyclerView adapter上添加HashMap

       private HashMap<String, String> txtValueMap = new HashMap<String, String>();

      onBindViewHolder 适配器

          @Override
public void onBindViewHolder(final ViewHolder holder, final int position) {

         final PanelVO item1 = (PanelVO) mDataArrayList.get(position);

         //set text on Exittext
         holder.et_panel.setText( item1.getPanelName() );

         //add key and value pair data on HashMap data list
         //using this line when you scroll listview not interchange Edittext data
         //if comment this line so input value in EditText swaps its position while scrolling in a RecyclerView

         txtValueMap.put(item1.getPanelId(),holder.et_panel.getText().toString());

         //add key and value pair data on txtValueMap 

        holder.et_panel.addTextChangedListener(new TextWatcher() {
                @Override
                public void beforeTextChanged(CharSequence s, int start, int count, int after) {

                }

                @Override
                public void onTextChanged(CharSequence s, int start, int before, int count) {

                }

                @Override
                public void afterTextChanged(Editable s) {

                        txtValueMap.put(item1.getPanelId(),holder.et_panel.getText().toString());
                        final PanelVO item1 = (PanelVO) mDataArrayList.get(position);

                        Iterator myVeryOwnIterator = txtValueMap.keySet().iterator();

                        while(myVeryOwnIterator.hasNext()) {

                            String key=(String)myVeryOwnIterator.next();
                            String value=(String) txtValueMap.get(key);

                            if(key.equalsIgnoreCase(item1.getPanelId())){
                                //update data in your listview
                                item1.setPanelName(holder.et_panel.getText().toString());
                            }
                        }
                }
            });


}

      【讨论】：

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