问题
After using the code below to refresh a ListField containing data returned in an xml web service. But after refresh or on refresh it sets focus to the first row in the ListField. I don't want that. I want it to maintain its current focus after refresh so that a user wont even know that there was a refresh.
protected void onUiEngineAttached(boolean attached) {
if (attached) {
// TODO: you might want to show some sort of animated
// progress UI here, so the user knows you are fetching data
Timer timer = new Timer();
// schedule the web service task to run every minute
timer.schedule(new WebServiceTask(), 0, 60*1000);
}
}
public MyScreen() {
setTitle("yQAforum");
listUsers.setEmptyString("No Users found", 0);
listUsers.setCallback(this);
add(listUsers);
}
private class WebServiceTask extends TimerTask {
public void run() {
//Fetch the xml from the web service
String wsReturnString = GlobalV.Fetch_Webservice("myDs");
//Parse returned xml
SAXParserImpl saxparser = new SAXParserImpl();
ByteArrayInputStream stream = new ByteArrayInputStream(wsReturnString.getBytes());
try {
saxparser.parse( stream, handler );
}
catch ( Exception e ) {
response.setText( "Unable to parse response.");
}
// now, update the UI back on the UI thread:
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
//Return vector sze from the handler class
listUsers.setSize(handler.getItem().size());
// Note: if you don't see the list content update, you might need to call
// listUsers.invalidate();
// here to force a refresh. I can't remember if calling setSize() is enough.
}
});
}
}
回答1:
As I suggested in the comments after my answer yesterday, you need to record the currently focused row before you refresh your list, and then set the focused row again, immediately after the update.
So, for example, in the WebServiceTask:
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
int currentIndex = listUsers.getSelectedIndex();
int scrollPosition = getMainManager().getVerticalScroll();
//Return vector sze from the handler class
listUsers.setSize(handler.getItem().size());
listUsers.setSelectedIndex(currentIndex);
getMainManager().setVerticalScroll(scrollPosition);
}
});
In the code you posted in your comment, you were calling setSelectedIndex() with the result of getSelectedIndex() after you did the refresh, which will never do what you want.
来源：https://stackoverflow.com/questions/14065908/blackberry-listfield-maintaining-row-focus-during-an-update