Android,ArrayAdapter的add()函数不能正常工作

Question

我有一个附加到AutoCompleteTextView(textView)组件的ArrayAdapter(myAdapter).
一旦用户按下一个字符,我想用包含该字符的项目填充AutoCompleteTextView的下拉列表.
我使用AsyncTask(使用Web服务)检索项目.

我调用myAdapter.add(item)但下拉列表为空.
我在每次添加后添加了一个调用myAdapter.getCount(),每次都显示为零.调用notifyDataSetChanged()没有帮助.
我甚至试图添加简单的String对象而不是我的自定义对象,但无济于事.
我究竟做错了什么？

编辑:我改变了代码,因为miette建议如下,但仍无济于事.
通常,我所做的是在自动完成文本视图中更改文本后,我调用一个新的AsyncTask并将输入的文本和Handler传递给它(请参阅afterTextChanged()).该任务检索与文本相关的对象,一旦完成Handler的handleMessage()被调用.在handleMessage()中,我尝试填充适配器的对象.但仍然适配器的下拉列表结束为空.

这是我的代码:

public class AddStockView extends Activity
        implements OnClickListener, OnItemClickListener, TextWatcher {  

    ArrayAdapter<Stock> adapter;
    AutoCompleteTextView textView;
    Vector<Stock> stocks;
    public AddStockView() {
      // TODO Auto-generated constructor stub
      stocks = new Vector<Stock>();
    }

    public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      requestWindowFeature(Window.FEATURE_NO_TITLE); 
      setContentView(R.layout.add_stock_view);

      findViewById(R.id.abort_button).setOnClickListener(this);

      adapter = new ArrayAdapter<Stock>(this,
      android.R.layout.simple_dropdown_item_1line, stocks);
      //adapter.setNotifyOnChange(true);
      textView = (AutoCompleteTextView)
      findViewById(R.id.search_edit_text);
      textView.setAdapter(adapter);
      textView.setOnItemClickListener(this);
      textView.addTextChangedListener(this);

    }
    @Override
    public void onClick(View v) {
      // TODO Auto-generated method stub
      switch (v.getId())
      {
        case R.id.abort_button:
        finish();
        break;
        case R.id.search_edit_text:

        break;
      }
    }
    @Override
    public void onItemClick(AdapterView<?> parent, View v,
                            int position, long id) {
      // TODO Auto-generated method stub
      Stock stockToAdd = (Stock)parent.getAdapter().getItem(position);
      //TODO: Add the above stock to user's stocks and close this screen
      finish();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {  
      super.onCreateOptionsMenu(menu);  
      getMenuInflater().inflate(R.layout.menu, menu);  

      CategoryMenu.getInstance().populateMenu(menu);
      return true;  
    }  

    @Override  
    public boolean onOptionsItemSelected(MenuItem item) {  
      CategoryMenu.getInstance().menuItemSelected(item, this);
      return false; 
    }  

    @Override  
    public boolean onPrepareOptionsMenu(Menu menu) { 
      return true;  
    }
    @Override
    public void afterTextChanged(Editable text) {
      // TODO Auto-generated method stub
      if (text.toString().equals(""))
        return;
      new AppTask().execute(new AppTask.Payload(Consts.taskType.SEARCH_STOCK,
                                          new Object[] {text, handler}, this));

    }
    @Override
    public void beforeTextChanged(CharSequence a0, int a1, int a2, int a3) {
      // TODO Auto-generated method stub
    }
    @Override
    public void onTextChanged(CharSequence a0, int a1, int a2, int a3) {
      // TODO Auto-generated method stub
    }
    private void addStockItemsToAdapter(Vector<Object> dataItems)
    {
      for (int i = 0; i <dataItems.size(); i++)
      {
        Stock stk = (Stock)dataItems.elementAt(i);
        stocks.add(stk);
      }
    }

    public void populateAdapter()
    {
      addStockItemsToAdapter(ContentReader.getInstance.getDataItems());    
      adapter.notifyDataSetChanged();
      int size = adapter.getCount(); // size == 0 STILL!!!!
      textView.showDropDown();
    }
    final Handler handler = new Handler() {
      public void handleMessage(Message msg) {
        populateAdapter();
      }
    };
}

非常感谢,Rob

Answer 1

我有同样的问题.在检查了ArrayAdapter和AutoCompleteTextView源代码后,我发现问题简而言之:

• 原始对象列表存储在ArrayAdapter.mObjects.
• 但是,AutoCompleteTextView启用ArrayAdapter过滤,意味着添加新对象ArrayAdapter.mOriginalValues,同时mObjects包含过滤后的对象.
• ArrayAdapter.getCount()总是返回大小mObjects.

我的解决方案是覆盖ArrayAdapter.getFilter()以返回非过滤过滤器.这种方式mOriginalValues是null和mObjects来代替在所有情况下.

示例代码:

public class MyAdapter extends ArrayAdapter<String> {
    NoFilter noFilter;
    /*
    ...
    */

    /**
     * Override ArrayAdapter.getFilter() to return our own filtering.
     */
    public Filter getFilter() {
        if (noFilter == null) {
            noFilter = new NoFilter();
        }
        return noFilter;
    }

    /**
     * Class which does not perform any filtering.
     * Filtering is already done by the web service when asking for the list,
     * so there is no need to do any more as well.
     * This way, ArrayAdapter.mOriginalValues is not used when calling e.g.
     * ArrayAdapter.add(), but instead ArrayAdapter.mObjects is updated directly
     * and methods like getCount() return the expected result.
     */
    private class NoFilter extends Filter {
        protected FilterResults performFiltering(CharSequence prefix) {
            return new FilterResults();
        }

        protected void publishResults(CharSequence constraint,
                                      FilterResults results) {
            // Do nothing
        }
    }
}

Answer 2

在哪里调用 addItemsToAdapter() ？您能否向我们展示您如何尝试将简单的字符串添加到适配器中？

编辑：在注释中提供有用的代码示例：

adapter = new ArrayAdapter<Stock>(this, android.R.layout.simple_dropdown_item_1line, stocks);
adapter.notifyDataSetChanged();
textView.setAdapter(adapter);