在Android ListView上使用过滤时出错？

Question

我正在尝试向Android应用程序中的列表视图添加过滤。它无法正常工作，因为在搜索框中写入3-4个字母后出现以下异常。

07-02 12:14:48.348: E/AndroidRuntime(22028): FATAL EXCEPTION: main
07-02 12:14:48.348: E/AndroidRuntime(22028): java.lang.IndexOutOfBoundsException: Invalid index 1, size is 1
07-02 12:14:48.348: E/AndroidRuntime(22028):    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at java.util.ArrayList.get(ArrayList.java:304)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.ArrayAdapter.getItem(ArrayAdapter.java:337)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at com.sphinx.indianrailways.adapters.CityAdapter.getView(CityAdapter.java:57)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.AbsListView.obtainView(AbsListView.java:2143)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.ListView.makeAndAddView(ListView.java:1831)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.ListView.fillDown(ListView.java:674)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.ListView.fillSpecific(ListView.java:1332)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.ListView.layoutChildren(ListView.java:1630)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.AbsListView.onLayout(AbsListView.java:1994)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.view.View.layout(View.java:14008)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.view.ViewGroup.layout(ViewGroup.java:4373)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1663)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1521)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.view.View.layout(View.java:14008)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.view.ViewGroup.layout(ViewGroup.java:4373)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.view.View.layout(View.java:14008)
07-02 12:14:48.348: E/AndroidRuntime(22028):    at android.view.ViewGroup.layout(ViewGroup.java:4373)

我的过滤代码如下所示：

filterTextWatcher = new TextWatcher() {

            @Override
            public void onTextChanged(CharSequence cs, int start, int before,
                    int count) {
                // When user changed the Text by typing in search box
                adapter.getFilter().filter(cs);
            }

            @Override
            public void beforeTextChanged(CharSequence arg0, int arg1,
                    int arg2, int arg3) {
                // TODO Auto-generated method stub

            }

            @Override
            public void afterTextChanged(Editable arg0) {
                // TODO Auto-generated method stub
            }
        };

        citySearchBox.addTextChangedListener(filterTextWatcher);

我的StationAdapter.java代码是：

    public class CityAdapter extends ArrayAdapter<City> {
    ArrayList<City> cityLists = new ArrayList<City>();
    private Context context;
    public String noInternet = "No network connectivity.Try again later.";
    City city= null;

    public CityAdapter(Context context, int textViewResourceId,
            ArrayList<City> cityLists) {
        super(context, textViewResourceId, cityLists);
        this.context = context;
        this.cityLists = cityLists;
    }

    static class ViewHolder {
        protected TextView cityCode;
        protected TextView cityName;
    }

    @Override
    public int getCount() {
        return cityLists.size();
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub

        ViewHolder holder = null;
        if (convertView == null) {
            LayoutInflater inflator = ((Activity) context).getLayoutInflater();
            convertView = inflator.inflate(R.layout.single_city_item, null);
            holder = new ViewHolder();

            holder.cityCode = (TextView) convertView
                    .findViewById(R.id.cityCode);
            holder.cityName = (TextView) convertView
                    .findViewById(R.id.cityName);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        city= getItem(position);

        holder.cityCode.setText(city.getCityCode());
        holder.cityName.setText(city.getCityName());
        return convertView;
    }
}

我知道arraylist当时可能只有1个元素，并且它试图通过list [1]访问它，这将引发nullpointerexception。但是我需要更改代码来解决此问题。

Answer 1

经过讨论，我认为问题就在这里：

 @Override
    public int getCount() {
        return cityLists.size();
    }

这使适配器认为它的大小大于正常大小（因为它的大小是固定的，并且在过滤后不会更改），并且在调用getView()（city= getItem(position);）时无法获得属于其范围的项。

你应该实现的Filterable接口（getFilter()）在问题1，2和这个例子。这将在cityLists每次getFilter()调用时更新Array ，其大小将正常返回，并且还将更新Adapter（notifyDataSetChanged()）

编辑

一种替代方法是删除您的getCount()（让super方法生效）。这将在每次应用过滤器时更新大小，而不是返回cityLists.size()固定的大小，并使适配器认为它的大小大于其拥有的数据。基本上，您既可以getCount()按照自己的方式实施，也可以在每次过滤时添加getFilter()更改cityLists大小，或者让系统同时处理这两种情况（不实施getFilter()也不实施getCount()）