Android - ListView 中的 EditTexts 绑定到自定义 ArrayAdapter - 跟踪更改

问题描述

我有一个 Android 活动，其中我有一个绑定到自定义 ArrayAdapter 的 ListView.ListView 的每一行都有两个 EditText(数字)字段.

I have an Android activity in which I have a ListView bound to a custom ArrayAdapter. Each row of the ListView has two EditText (numeric) fields.

ArrayAdapter 最初是从 SQLite DB 填充的.但是，用户可以在 ListView 的末尾添加一行，或者(通过长按一行)删除 ListView 中的任何行.当他们点击保存"按钮时，他们的更改会被保留.

The ArrayAdapter is initially populated from an SQLite DB. However the user can add a row at the end of the ListView, or (by long-pressing on a row) delete any row in the ListView. When they hit the 'Save' button, their changes are persisted.

我正在跟踪所做的更改，方法是将 AfterTextChanged() 事件的 CustomTextWatcher 附加到 ArrayAdapter 的 getView() 方法中的每个 EditText(传入 EditText 和 ArrayAdapter 的项目列表中的相应对象)，然后将该对象的匹配属性设置为 EditText 的内容.这样在保存时，我可以简单地遍历底层对象列表并进行适当的数据库更改，知道对象列表是最新的.

I am keeping track of changes as they are made by attaching a CustomTextWatcher for the AfterTextChanged() event to each EditText in the ArrayAdapter's getView() method (passing in the EditText and the corresponding object in the ArrayAdapter's item list) and then setting the matching property of that object to the content of the EditText. This is so that on saving I can simply iterate through the underlying object list and make the appropriate DB changes, knowing that the object list is up-to-date.

适配器类和 CustomTextWatcher 的代码:

Code for the adapter class and the CustomTextWatcher:

private class CustomAdapter extends ArrayAdapter<DataItem> {
    private ArrayList<DataItem> items;

    public CustomAdapter(Context context, int textViewResourceId, ArrayList<DataItem> items) {
        super(context, textViewResourceId, items);
        this.items = items;
}

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
            View v = convertView;

            DataItem wed = items.get(position);

            if (v == null) {
                LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                v = vi.inflate(R.layout.log_exercise_row, null);
            }

            if(wed != null)
            {
                     EditText text1 = (EditText) v.findViewById(R.id.text1);
                     EditText text2 = (EditText) v.findViewById(R.id.text2);

                text1.addTextChangedListener(new CustomTextWatcher(text1,wed));
                text2.addTextChangedListener(new CustomTextWatcher(text2,wed));


                int weight = wed.getWeight();

                if(weight != -1)
                {
                   text1.setText(weight+"");
                }


                int reps = wed.getReps();

                if(reps != -1)
                {
                    text2.setText(reps+"");
                }


            }

            return v;
    }

private class CustomTextWatcher implements TextWatcher {

    private EditText EditText; 
    private DataItem item;

    public CustomTextWatcher(EditText e, DataItem item)
    {
        this.EditText = e;
        this.item = item;
    }

    @Override
    public void afterTextChanged(Editable arg0) {

        String text = arg0.toString();

        if(text != null && text.length() > 0)
        {
            int val;

            try
            {
                val =Integer.parseInt(text);
            }

            catch(NumberFormatException e)
            {
                val=-1;
            }

            if(EditText.getId()==R.id.weightEditText)
            {
                item.setWeight(val);
            }

            else if(EditText.getId()==R.id.repsEditText)
            {
                item.setRepetitions(val);
            }
        }
    }

这一切都很好，除非在发生不需要的 EditText 内容重复时添加或删除项目.

This all works fine except when items are added or deleted when unwanted duplication of EditText content happens.

举例说明:

从 3 行开始，EditText 全部为空
在第 2 行中，输入5"、6"
单击更多"-> 在末尾添加一个(空)行.现在有 4 行.
删除最后一行->显示的 3 行，但第 2 行和第 3 行现在显示 '5'、'6'->???????

Start with 3 rows, EditText's all empty
In row 2, enter '5', '6'
Click 'More'->Adds an (empty) row on the end. Now 4 rows.
Delete last row->3 rows displayed, BUT 2nd AND 3rd rows now display '5', '6'->???????

看起来 EditText 对象在 ListView 中的相对位置在重新绑定后不稳定，这是导致问题的原因.例如.EditText 对象X"从位置 3 开始，然后在重新绑定后位于位置 1 - 但它仍然附有一个 CustomTextWatcher，引用位置 3 中的数据对象.另一个问题是 addTextChangedListener() 不影响TextWatchers 已附加到 EditText.

It looks like the relative position of EditText objects within the ListView is not stable after rebinding which is causing the problem. E.g. EditText object 'X' starts in position 3, then after a rebind it is in position 1 - but it still has a CustomTextWatcher attached to it referencing the data object in position 3. The other issue is the fact that addTextChangedListener() does not affect the TextWatchers already attached to the EditText.

我对 Android 很陌生，所以我不确定是否有更好的方法来解决我的问题.任何帮助表示赞赏.

I'm pretty new to Android, so I'm not sure if there is a better approach to solve my problem. Any help is appreciated.

推荐答案

看起来我需要一个自定义 ('ViewHolder') 类来保持 EditText 及其关联数据对象之间的引用在每个对象上正确同步绑定"数据.此外，当在 getView() 方法中的 convertView 对象为 null 时放置事件侦听器调用意味着每个 EditText 对象仅添加一个侦听器.

It looks like a custom ('ViewHolder') class was what I needed in order to keep the references between a EditText and its associated data object properly synchronised on each 'bind' of the data. Also, placing the event listener calls when the convertView object was null in the getView() method meant only one listener was added per EditText object.

感谢 http://www.vogella.de/articles/AndroidListView/article.html#listsactivity 为我指明了正确的方向.

Thanks to http://www.vogella.de/articles/AndroidListView/article.html#listsactivity for pointing me in the right direction.

public class CustomAdapter extends ArrayAdapter<DataItem> {
private ArrayList<DataItem> items;
private Activity Context;

public CustomAdapter(Activity context, int textViewResourceId, ArrayList<DataItem> items) {
    super(context, textViewResourceId, items);
    this.items = items;
    this.Context = context; 
}

static class ViewHolder {
    protected EditText weight;
    protected EditText reps;

}

 public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;

        DataItem wed = items.get(position);


        if (v == null) {
            LayoutInflater inflator = Context.getLayoutInflater();
            v = inflator.inflate(R.layout.log_exercise_row, null);
            final ViewHolder viewHolder = new ViewHolder();
            viewHolder.text1 = (EditText) v.findViewById(R.id.text1);
            viewHolder.text2 = (EditText) v.findViewById(R.id.text2);


            viewHolder.text1.addTextChangedListener(new CustomTextWatcher(viewHolder, viewHolder.text1));
            viewHolder.text2.addTextChangedListener(new CustomTextWatcher(viewHolder, viewHolder.text2));

            v.setTag(viewHolder);
            viewHolder.text1.setTag(wed);
            viewHolder.text2.setTag(wed);

        }

        else
        {
            ViewHolder holder = (ViewHolder) v.getTag();
            holder.text1.setTag(wed);
            holder.text2.setTag(wed);   
        }

        ViewHolder holder = (ViewHolder) v.getTag();

        // set values

        if(wed.getWeight() != -1)
        {
            holder.text1.setText(wed.getWeight()+"");
        }

        else
        {
            holder.weight.setText("");
        }

        if(wed.getRepetitions() != -1)
        {
            holder.text2.setText(wed.getRepetitions()+"");
        }

        else
        {
            holder.reps.setText("");
        }

        return v;
}

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