android - 将 Cursor 与 ListView 适配器一起用于大量数据

Question

我正在使用自定义 CursorAdapter 从 SQLite 数据库中获取数据并将其显示在 ListView 中。该数据库包含 2 列，大约 8.000 行。所以我正在寻找一种方法来尽快查询和显示所有数据。我已经用 asyncTask 完成了这里的代码:

private class PrepareAdapter extends AsyncTask<Void,Void,CustomCursorAdapter > {

 @Override
 protected void onPreExecute() {
     dialog.setMessage("Wait");
     dialog.setIndeterminate(true);
     dialog.setCancelable(false);
     dialog.show();


     Log.e("TAG","Posle nov mAdapter");
 }

 @Override
 protected CustomCursorAdapter doInBackground(Void... unused) {

   Cursor cursor =  myDbNamesHelper.getCursorQueryWithAllTheData();
   mAdapter.changeCursor(cursor);
   startManagingCursor(cursor);
   Log.e("TIME","posle start managing Cursor" + String.valueOf(SystemClock.elapsedRealtime()-testTime)+ " ms");
     testTime=SystemClock.elapsedRealtime();

     mAdapter.initIndexer(cursor);
     return mAdapter;
 }

 protected void onPostExecute(CustomCursorAdapter result) {

     TabFirstView.this.getListView().setAdapter(result);
     Log.e("TIME","posle adapterSet" + String.valueOf(SystemClock.elapsedRealtime()-testTime)+ " ms");
    testTime=SystemClock.elapsedRealtime();
     dialog.dismiss();
 }

除了我需要将结果设置到适配器中的部分外，这很好用。我做了一些时间测试，它需要大约 700 毫秒才能通过 startManagingCursor。问题是它需要大约 7 秒才能通过 setAdapter(result)，并且它在 UI 线程中运行，因此它使我的应用程序无响应(进度对话框卡住，有时应用程序会响应)。我怎样才能减少这个时间？我可以让它在后台运行或以任何方式提高响应能力吗？

谢谢。

public class CustomCursorAdapter extends SimpleCursorAdapter implements OnClickListener,SectionIndexer,Filterable,
                                    android.widget.AdapterView.OnItemClickListener{

    private Context context;
    private int layout;
    private AlphabetIndexer alphaIndexer;

    public CustomCursorAdapter (Context context, int layout, Cursor c, String[] from, int[] to) {
        super(context, layout, c, from, to);
        this.context = context;
        this.layout = layout;

    }
    public void initIndexer(Cursor c){
         alphaIndexer=new AlphabetIndexer(c, c.getColumnIndex(DataBaseNamesHelper.COLUMN_NAME), " ABCDEFGHIJKLMNOPQRSTUVWXYZ");
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {

        Cursor c = getCursor();

        final LayoutInflater inflater = LayoutInflater.from(context);
        View v = inflater.inflate(layout, parent, false);

        int nameCol = c.getColumnIndex(DataBaseNamesHelper.COLUMN_NAME);

        String name = c.getString(nameCol);

        /**
         * Next set the name of the entry.
         */
        TextView name_text = (TextView) v.findViewById(R.id.name_entry);
        if (name_text != null) {
            name_text.setText(name);
        }

        int favCol = c.getColumnIndex(DataBaseNamesHelper.COLUMN_FAVOURITED);
        int fav = c.getInt(favCol);

        int idCol = c.getColumnIndex(DataBaseNamesHelper.COLUMN_ID);

        Button button = (Button) v.findViewById(R.id.Button01);
        button.setOnClickListener(this);
        button.setTag(c.getInt(idCol));
        if(fav==1){
            button.setVisibility(View.INVISIBLE);
        }
        else button.setVisibility(View.VISIBLE);

        return v;
    }

    @Override
    public void bindView(View v, Context context, Cursor c) {

        int nameCol = c.getColumnIndex(DataBaseNamesHelper.COLUMN_NAME);

        String name = c.getString(nameCol);

        /**
         * Next set the name of the entry.
         */
        TextView name_text = (TextView) v.findViewById(R.id.name_entry);
        if (name_text != null) {
            name_text.setText(name);
        }
        int favCol = c.getColumnIndex(DataBaseNamesHelper.COLUMN_FAVOURITED);
        int fav = c.getInt(favCol);

        Button button = (Button) v.findViewById(R.id.Button01);
        button.setOnClickListener(this);
        int idCol = c.getColumnIndex(DataBaseNamesHelper.COLUMN_ID);
        button.setTag(c.getInt(idCol));
      //  Log.e("fav",String.valueOf(fav));
        if(fav==1){
            button.setVisibility(View.INVISIBLE);
        } else button.setVisibility(View.VISIBLE);
    }



    @Override
    public int getPositionForSection(int section) {
        return alphaIndexer.getPositionForSection(section);
    }

    @Override
    public int getSectionForPosition(int position) {
          return alphaIndexer.getSectionForPosition(position);
    }

    @Override
    public Object[] getSections() {
          return alphaIndexer.getSections();
    }
    @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
        Log.e("item Click", arg1.toString()+ " position> " +arg2);
    }

    @Override
    public void onClick(View v) {
            if(v.getId()==R.id.Button01){
                //Log.e("Button Click", v.toString()+ " position> " +v.getTag().toString());
                v.setVisibility(View.INVISIBLE);
                DataBaseNamesHelper dbNames = new DataBaseNamesHelper(context);
                dbNames.setFavouritesFlag(v.getTag().toString());
            }

        }



}

Answer 1

加载适配器缓慢的原因是 CursorAdapter 对 Cursor.getCount() 进行的内部调用。

Android 中的游标是延迟加载的。直到需要时才会加载结果。当 CursorAdapter 调用 getCount() 时，这会强制完全执行查询并对结果进行计数。

下面是讨论这个问题的几个链接。

http://groups.google.com/group/android-developers/browse_thread/thread/c1346ec6e2310c0c

http://www.androidsoftwaredeveloper.com/2010/02/25/sqlite-performance/

我的建议是拆分您的查询。仅加载屏幕上可见列表项的数量。随着用户滚动加载下一组。非常像 GMail 和 Market 应用程序。不幸的是我手边没有例子:(

这并没有回答你的问题，但希望它能提供一些见解:)