我编写了一个具有自定义列表适配器的 ListActivity。运行 onCreate 时，列表正在从 ContentProvider 更新。我还有一个服务，它在我运行应用程序时启动，它首先更新 ContentProvider，然后发送内容已更新的广播。
我的 ListActivity 接收到广播并尝试更新我的 ListView。我的问题是，在没有通知 ListView 的情况下，我收到有关 ListView 适配器数据更改的间歇性错误。我打电话给notifyDataSetChanged()更新后立即在我的列表适配器上使用方法。看起来正在发生的事情是，当它从服务接收到要更新的广播时，第一次调用 onCreate 后，列表仍在更新过程中，因此它会在从第一次运行完成更新之前尝试更新我的 ListView。这有意义吗？这是我的一些代码。
注意：该服务工作正常，它会获取新数据并更新我的 ContentProvider，并且在更新时我会在我的活动中收到广播。
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ctx = this;
getPrefs();
setContentView(R.layout.main);
// Setup preference listener
preferences = PreferenceManager.getDefaultSharedPreferences(this);
preferences.registerOnSharedPreferenceChangeListener(listener);
// Setup report list adapter
ListView nzbLv = (ListView) findViewById(R.id.report_list);
nzbla = new NZBReportListAdaptor(ctx);
getReports();
nzbla.setListItems(report_list);
nzbLv.setAdapter(nzbla);
// Broadcast receiver to get notification from NZBService to update ReportList
registerReceiver(receiver,
new IntentFilter(NZBService.BROADCAST_ACTION));
startService(new Intent(ctx, NZBService.class));
}
@Override
public void onResume() {
super.onResume();
timerHandler.resume();
new updateSabQueue().execute();
//updateList();
}
@Override
public void onPause() {
super.onPause();
timerHandler.pause();
unregisterReceiver(receiver);
}
private BroadcastReceiver receiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
Toast.makeText(ctx, "NZBService broadcast recieved", Toast.LENGTH_SHORT).show();
updateReportList();
}
};
private void updateReportList() {
new updateReportList().execute();
}
private class updateReportList extends AsyncTask<Void, Void, Boolean> {
/* (non-Javadoc)
* @see android.os.AsyncTask#onPreExecute()
* Show progress dialog
*/
protected void onPreExecute() {
}
/* (non-Javadoc)
* @see android.os.AsyncTask#doInBackground(Params[])
* Get new articles from the internet
*/
protected Boolean doInBackground(Void...unused) {
getReports();
return true;
}
/**
* On post execute.
* Close the progress dialog
*/
@Override
protected void onPostExecute(Boolean updated) {
if (updated) {
Log.d(TAG, "NZB report list adapter updated");
synchronized(this) {
nzbla.setListItems(report_list);
}
Log.d(TAG, "NZB report list notified of change");
nzbla.notifyDataSetChanged();
}
}
}
现在这个问题已经得到解答，我将发布我更新的代码，以帮助可能遇到它的其他人。
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ctx = this;
getPrefs();
setContentView(R.layout.main);
// Setup preference listener
preferences = PreferenceManager.getDefaultSharedPreferences(this);
preferences.registerOnSharedPreferenceChangeListener(listener);
// Setup report list adapter
ListView nzbLv = (ListView) findViewById(R.id.report_list);
nzbla = new NZBReportListAdaptor(ctx);
report_list.addAll(getReports());
nzbla.setListItems(report_list);
nzbLv.setAdapter(nzbla);
// Broadcast receiver to get notification from NZBService to update ReportList
registerReceiver(receiver,
new IntentFilter(NZBService.BROADCAST_ACTION));
startService(new Intent(ctx, NZBService.class));
}
private class updateReportList extends AsyncTask<Void, Void, ArrayList<Report>> {
/* (non-Javadoc)
* @see android.os.AsyncTask#onPreExecute()
* Show progress dialog
*/
protected void onPreExecute() {
}
/* (non-Javadoc)
* @see android.os.AsyncTask#doInBackground(Params[])
* Get new articles from the internet
*/
protected ArrayList<Report> doInBackground(Void...unused) {
return getReports();
}
/**
* On post execute.
* Close the progress dialog
*/
@Override
protected void onPostExecute(ArrayList<Report> updated) {
nzbla.setListItems(updated);
nzbla.notifyDataSetChanged();
}
}
private ArrayList<Report> getReports() {
ArrayList<Report> reports = new ArrayList<Report>();
ContentResolver r = getContentResolver();
Cursor c = r.query(NZBReportProvider.CONTENT_URI, null, null, null, NZBReportProvider.ARTICLE_KEY_ROWID + " DESC");
startManagingCursor(c);
Log.d(TAG, "NZBReport cursor.getCount=" + c.getCount());
int title = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_TITLE);
int desc = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_DESCRIPTION);
int cat = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_CAT);
int size = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_SIZE);
int link = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_LINK);
int catid = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_CATID);
int date = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_DATE_ADDED);
int group = c.getColumnIndex(NZBReportProvider.ARTICLE_KEY_GROUP);
if (c.getCount() > 0) {
c.moveToFirst();
do {
URL url = null;
try {
url = new URL(c.getString(link));
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
reports.add(new Report(c.getString(title), url, c.getString(desc), c.getString(cat), c.getString(date), c.getString(size), c.getInt(catid), c.getString(group)));
} while (c.moveToNext());
}
return reports;
}