我有 10,000 行的数据库表，我想在列表视图中显示。我想显示前 20 个，当用户向下滚动到最后一个项目时，应该加载下一个 20（依此类推）。加载列表视图中的所有数据确实需要很多时间，所以这就是为什么我希望它首先加载 20 个数据..
在 onCreate() 方法里面的代码是：
dbHelper = new WordDbAdapter(this);
dbHelper.open();
//Generate ListView from SQLite Database
displayListView();
然后在 displayListView() 方法上的代码是这样的：
@SuppressWarnings("deprecation")
private void displayListView() {
final Cursor cursor = dbHelper.fetchAllWords();
// The desired columns to be bound
String[] columns = new String[] {
WordDbAdapter.KEY_WORD,
WordDbAdapter.KEY_ROWID,
};
// the XML defined views which the data will be bound to
int[] to = new int[] {
R.id.Word,
R.id.imgStar,
};
// create the adapter using the cursor pointing to the desired data
//as well as the layout information
dataAdapter = new SimpleCursorAdapter(
this, R.layout.word_info,
cursor,
columns,
to
);
ListView listView = (ListView) findViewById(R.id.Diclist);
// Assign adapter to ListView
listView.setAdapter(dataAdapter);
listView.setOnScrollListener(new OnScrollListener(){
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
int lastInScreen = firstVisibleItem + visibleItemCount;
if(cursor != null){
if(lastInScreen == totalItemCount && isLoadingMore == false){
isLoadingMore = true;
loadedPage ++;
new LoadWords().execute();
}
}
}
public void onScrollStateChanged(AbsListView view, int scrollState) {}
});
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> listView, View view,
int position, long id) {
// Get the cursor, positioned to the corresponding row in the result set
Cursor cursor = (Cursor) listView.getItemAtPosition(position);
// Get the word name from this row in the database.
String wordSelected =
cursor.getString(cursor.getColumnIndexOrThrow("word"));
String wordSyllabication =
cursor.getString(cursor.getColumnIndexOrThrow("syllabication"));
String wordPartofSpeech =
cursor.getString(cursor.getColumnIndexOrThrow("partofspeech"));
String wordMeaning =
cursor.getString(cursor.getColumnIndexOrThrow("meaning"));
String wordSpeak =
cursor.getString(cursor.getColumnIndexOrThrow("speakword"));
EditText TextDic = (EditText) findViewById(R.id.TextDic);
TextDic.setText(wordSelected);
speakMeaning = wordMeaning;
speakSyllabication = wordSyllabication;
speakPartOfSpeech = wordPartofSpeech;
speakWord = wordSpeak;
speakGetWord = wordSelected;
//Toast.makeText(getApplicationContext(),
// wordSyllabication + "\n" + wordPartofSpeech + "\n" + wordMeaning , Toast.LENGTH_SHORT).show();
}
});
EditText TextDic = (EditText) findViewById(R.id.TextDic);
TextDic.addTextChangedListener(new TextWatcher() {
public void afterTextChanged(Editable s) {
speakWord = "";
speakMeaning = "";
}
public void beforeTextChanged(CharSequence s, int start,
int count, int after) {
}
public void onTextChanged(CharSequence s, int start,
int before, int count) {
dataAdapter.getFilter().filter(s.toString());
}
});
dataAdapter.setFilterQueryProvider(new FilterQueryProvider() {
public Cursor runQuery(CharSequence constraint) {
return dbHelper.fetchWordsByWord(constraint.toString());
}
});
}
那么我的 AsyncTask 是这样的：
private class LoadWords extends AsyncTask<String, Void, Void> {
private final ProgressDialog dialog = new ProgressDialog(DictionaryActivity.this);
Cursor cursor = dbHelper.fetchAllWords();
@Override
protected void onPreExecute() {
this.dialog.setMessage("Loading books...");
this.dialog.show();
}
public void execute() {
// TODO Auto-generated method stub
}
@Override
protected Void doInBackground(String... arg0) {
try{
cursor = dbHelper.fetchAllWords();
}catch(Exception e){
e.printStackTrace();
}
return null;
}
@SuppressWarnings("deprecation")
@Override
protected void onPostExecute(final Void unused){
if(cursor != null){
if(dataAdapter == null){
startManagingCursor(cursor);
String[] columns = new String[] {
WordDbAdapter.KEY_WORD,
WordDbAdapter.KEY_ROWID,
};
int[] to = new int[] {
R.id.Word,
R.id.imgStar,
};
getListView().setTranscriptMode(ListView.TRANSCRIPT_MODE_NORMAL);
dataAdapter = new SimpleCursorAdapter(DictionaryActivity.this, R.layout.word_info, cursor, columns, to);
ListView listView = (ListView) findViewById(R.id.Diclist);
// Assign adapter to ListView
listView.setAdapter(dataAdapter);
}else{
dataAdapter.notifyDataSetChanged();
}
}
if(dialog != null && dialog.isShowing()){
dialog.dismiss();
}
isLoadingMore = false;
}
private AbsListView getListView() {
// TODO Auto-generated method stub
return null;
}
}