问题描述
我正在使用自定义 CursorAdapter 从 SQLite 数据库获取数据并将其显示在列表视图中.该数据库包含 2 列，大约有 8.000 行.所以我正在寻找一种尽可能快地查询和显示所有数据的方法.我已经用 asyncTask 做到了这里是代码:
i am using a custom CursorAdapter to get data from a SQLite database and show it in a listview. The database contains a 2 columns with about 8.000 rows. so i am looking for a way to query and show all the data as fast as possible. i have done this with asyncTask here is the code:
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();
}
}
这很好用，除了我需要将结果设置到适配器的部分.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(进度对话框冻结，有时应用程序执行).我如何减少这个时间?我可以让它在后台运行或以任何方式提高响应速度吗?
this works good except the part when i need to set the result into an adapter. i have done some time tests and it takes aprox 700 ms to make it past the startManagingCursor. the problem is that it takes about 7 seconds to make it past the setAdapter(result) and this is running in UI thread so it makes my app unresponsive (the progress dialog freezes and sometimes does the app). how do i make this time less? can i make this also run in background or any way to increase responsiveness?
tnx.
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());
}
}
}
推荐答案
加载适配器时间慢的原因是 CursorAdapter 对 Cursor.getCount() 进行的内部调用.
The reason for the slow time in loading the adapter is the internal call the CursorAdapter makes to Cursor.getCount().
Android 中的游标是延迟加载的.结果在需要时才会加载.当 CursorAdapter 调用 getCount() 时，这会强制完全执行查询并对结果进行计数.
Cursors in Android are lazily loaded. The results are not loaded until they are needed. When the CursorAdapter calls getCount() this forces the query to be fully executed and the results counted.
以下是讨论这个问题的几个链接.
Below are a couple links discussing this very issue.
http://groups.google.com/group/android-开发人员/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，我没有一个方便的例子:(
My suggestion would be to split up your query. Load only the number of visible list items on screen. As the user scrolls load the next set. Very much like the GMail and Market applications. Unfortunately I don't have an example handy :(
这不能回答您的问题，但希望它提供一些见解:)
This doesn't answer your question but hopefully it provides some insight :)
这篇关于使用 Cursor 和 ListView 适配器处理大量数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！