Develop Reference

buttons in listView not always triggered

I have a listview and in each cell it has a RelativeLayout with 7 buttons.
before the list is scrolled all the buttons work fine (all trigger when clicked) for all visible listView items, but after listView was scrolled some items turn to not clickable (no matter which button in the item I click), and it's random, after another scroll the same item can turn clickable, and other which was before turns to not clickable.
I have noticed that it usually happens (item turns not clickable) after scrolling all the way up.
Another thing that i have noticed that seldom (after 4-5 unsuccessful clicks in a row) the button triggers a few times in a row (like it was delayed). But usually it's not happening after a number of unsuccessful clicks.
In my original code I created an arrayList of RelativeLayouts (each for listView Item), and put the arrayList into adapter. For every 7 buttons (for each cell) I set 7 ids corresponding to their's place in arraylist.
In that way I implemented the OnClick event in the main class.
Here is 3 buttons (out of 7):
for (int i = 0; i < EXPEND_BUTTONS.length; i++) {
if (view.getId() == EXPEND_BUTTONS[i]) {
handleEmojiPanel(i);
break;
}
if (view.getId() == BUTTONS[i] || view.getId() == IMAGES[i]) {
ShowTopItem item = new ShowTopItem(getActivity(), i);
item.show();
break;
}
}
Because of the problem I change the code.
I handled the OnClick event for the buttons in the adapter itself in the getView method (for 2 buttons only):
public View getView(final int position, View convertView, ViewGroup parent) {
pos = position;
Button btn = (Button) listOfObjects.get(position).getChildAt(0);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
ShowTopItem item = new ShowTopItem(getActivity(), position + listChosen);
item.show();
}
});
Button imageBtn = (Button) listOfObjects.get(position).getChildAt(2);
imageBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
ShowTopItem item = new ShowTopItem(getActivity(), position + listChosen);
item.show();
}
});
return listOfObjects.get(position);
}
I have the same result. Nothing changed.
I have looked all over the internet, and it seems that I'm the only one who encountered such issue.
Id anybody knows what can be the issue here?
If some other code is needed, please feel free to ask.

I did not find the reason, but I changed ListView to ScrollView, and all works fine now.
Maybe there is some kind of bug in ListView, but in this case, I wonder why I did not find any complains regarding it.
Anyway, works perfect with ScrollView.

ListView with date as section headers position varies onScroll

Im trying to load custom callLogs in a listView based on date as section header.In ListAdapter i compare each date with the previous date and set SectionHeaderLayout Visible/Invisible. When the ListView has been loaded the section header are displayed correctly but when i scroll the section headers are set Visible to wrong ListItems.
Please help me to figure out a solution.
This is how im trying to set SectionHeader through the adapter.
if (position == 0) {
checkDate = mDateStr;
holder.sectionHeaderDate.setVisibility(View.VISIBLE);
holder.sectionHeaderText.setText(mDateStr);
}
} else if (checkDate == null || !checkDate.equals(mDateStr)) {
checkDate = mDateStr;
holder.sectionHeaderDate.setVisibility(View.VISIBLE);
holder.sectionHeaderText.setText(mDateStr);
} else {
holder.sectionHeaderDate.setVisibility(View.GONE);
}
Thanks in Advance

I see this is old question, you have probably solved your problem, but I'll answer for others who will have the same problem.
If you want to show header based on previous date you can't do that by remembering last item that was passed to getView function.
The reason is scrolling, i.e. different direction when going up and down.
For example, if you have items
1,
2,
3,
4,
5
when you're going down, and current item is 3, previous was 2, and all will work.
But if you are going up, your previous item for 3 was actually 4, and that's where your problem happens.
so instead of keeping item, you should use positions.
this would be the sketch of solution that you can call inside of your getView function:
private void showHeader(ViewHolder holder, Call item, int position) {
boolean shouldShowHeader = false;
if (position == 0
|| !DateHelper.isSameDay(item.getDateTime(),
items.get(position - 1).getDateTime()))
shouldShowHeader = true;
if (shouldShowHeader) {
holder.header.setVisibility(View.VISIBLE);
holder.date.setText(DateHelper.getSimpleDate(item.getDateTime()));
} else {
holder.header.setVisibility(View.GONE);
}
}

Adding items to ListView, maintaining scroll position and NOT seeing a scroll jump

I'm building an interface similar to the Google Hangouts chat interface. New messages are added to the bottom of the list. Scrolling up to the top of the list will trigger a load of previous message history. When the history comes in from the network, those messages are added to the top of the list and should not trigger any kind of scroll from the position the user had stopped when the load was triggered. In other words, a "loading indicator" is shown at the top of the list:
Which is then replaced in-situ with any loaded history.
I have all of this working... except one thing that I've had to resort to reflection to accomplish. There are plenty of questions and answers involving merely saving and restoring a scroll position when adding items to the adapter attached to a ListView. My problem is that when I do something like the following (simplified but should be self-explanatory):
public void addNewItems(List<Item> items) {
final int positionToSave = listView.getFirstVisiblePosition();
adapter.addAll(items);
listView.post(new Runnable() {
#Override
public void run() {
listView.setSelection(positionToSave);
}
});
}
Then what the user will see is a quick flash to the top of the ListView, then a quick flash back to the right location. The problem is fairly obvious and discovered by many people: setSelection() is unhappy until after notifyDataSetChanged() and a redraw of ListView. So we have to post() to the view to give it a chance to draw. But that looks terrible.
I've "fixed" it by using reflection. I hate it. At its core, what I want to accomplish is reset the first position of the ListView without going through the rigamarole of the draw cycle until after I've set the position. To do that, there's a helpful field of ListView: mFirstPosition. By gawd, that's exactly what I need to adjust! Unfortunately, it's package-private. Also unfortunately, there doesn't appear to be any way to set it programmatically or influence it in any way that doesn't involve an invalidate cycle... yielding the ugly behavior.
So, reflection with a fallback on failure:
try {
Field field = AdapterView.class.getDeclaredField("mFirstPosition");
field.setAccessible(true);
field.setInt(listView, positionToSave);
}
catch (Exception e) { // CATCH ALL THE EXCEPTIONS </meme>
e.printStackTrace();
listView.post(new Runnable() {
#Override
public void run() {
listView.setSelection(positionToSave);
}
});
}
}
Does it work? Yes. Is it hideous? Yes. Will it work in the future? Who knows? Is there a better way? That's my question.
How do I accomplish this without reflection?
An answer might be "write your own ListView that can handle this." I'll merely ask whether you've seen the code for ListView.
EDIT: Working solution with no reflection based on Luksprog's comment/answer.
Luksprog recommended an OnPreDrawListener(). Fascinating! I've messed with ViewTreeObservers before, but never one of these. After some messing around, the following type of thing appears to work quite perfectly.
public void addNewItems(List<Item> items) {
final int positionToSave = listView.getFirstVisiblePosition();
adapter.addAll(items);
listView.post(new Runnable() {
#Override
public void run() {
listView.setSelection(positionToSave);
}
});
listView.getViewTreeObserver().addOnPreDrawListener(new OnPreDrawListener() {
#Override
public boolean onPreDraw() {
if(listView.getFirstVisiblePosition() == positionToSave) {
listView.getViewTreeObserver().removeOnPreDrawListener(this);
return true;
}
else {
return false;
}
}
});
}
Very cool.

As I said in my comment, a OnPreDrawlistener could be another option to solve the problem. The idea of using the listener is to skip showing the ListView between the two states(after adding the data and after setting the selection to the right position). In the OnPreDrawListener(set with listViewReference.getViewTreeObserver().addOnPreDrawListener(listener);) you'll check the current visible position of the ListView and test it against the position which the ListView should show. If those don't match then make the listener's method return false to skip the frame and set the selection on the ListView to the right position. Setting the proper selection will trigger the draw listener again, this time the positions will match, in which case you'd unregister the OnPreDrawlistener and return true.

I was breaking up my head until I found a solution similar to this.
Before adding a set of items you have to save top distance of the firstVisible item and after adding the items do setSelectionFromTop().
Here is the code:
// save index and top position
int index = mList.getFirstVisiblePosition();
View v = mList.getChildAt(0);
int top = (v == null) ? 0 : v.getTop();
// for (Item item : items){
mListAdapter.add(item);
}
// restore index and top position
mList.setSelectionFromTop(index, top);
It works without any jump for me with a list of about 500 items :)
I took this code from this SO post: Retaining position in ListView after calling notifyDataSetChanged

The code suggested by the question author works, but it's dangerous.
For instance, this condition:
listView.getFirstVisiblePosition() == positionToSave
may always be true if no items were changed.
I had some problems with this aproach in a situation where any number of elements were added both above and below the current element. So I came up with a sligtly improved version:
/* This listener will block any listView redraws utils unlock() is called */
private class ListViewPredrawListener implements OnPreDrawListener {
private View view;
private boolean locked;
private ListViewPredrawListener(View view) {
this.view = view;
}
public void lock() {
if (!locked) {
locked = true;
view.getViewTreeObserver().addOnPreDrawListener(this);
}
}
public void unlock() {
if (locked) {
locked = false;
view.getViewTreeObserver().removeOnPreDrawListener(this);
}
}
#Override
public boolean onPreDraw() {
return false;
}
}
/* Method inside our BaseAdapter */
private updateList(List<Item> newItems) {
int pos = listView.getFirstVisiblePosition();
View cell = listView.getChildAt(pos);
String savedId = adapter.getItemId(pos); // item the user is currently looking at
savedPositionOffset = cell == null ? 0 : cell.getTop(); // current item top offset
// Now we block listView drawing until after setSelectionFromTop() is called
final ListViewPredrawListener predrawListener = new ListViewPredrawListener(listView);
predrawListener.lock();
// We have no idea what changed between items and newItems, the only assumption
// that we make is that item with savedId is still in the newItems list
items = newItems;
notifyDataSetChanged();
// or for ArrayAdapter:
//clear();
//addAll(newItems);
listView.post(new Runnable() {
#Override
public void run() {
// Now we can finally unlock listView drawing
// Note that this code will always be executed
predrawListener.unlock();
int newPosition = ...; // Calculate new position based on the savedId
listView.setSelectionFromTop(newPosition, savedPositionOffset);
}
});
}

scroll to list item in AlertDialog without selection

I have a huge list of items that I present in an AlertDialog. I would like to present the user the list scrolled to the most likely area they will select one item from. I'm using
AlertDialog.Builder.setSingleChoiceItems(myAdapter, ...).
ArrayAdapter<MyType> myAdapter;
The problem I'm having a hard time with is how to scroll to an item when it's not logically correct to present the item as selected.
I tried getting the ListView from the resulting AlertDialog. But it's empty (even after the Builder creates and shows it).
I tried forcing a populated ListView by inflating a plane ListView in res/layout. listView.scrollTo(x, y) didn't seem to have an effect.
I tried up setting the OnShowListener for the AlertDialog. onShow() is never invoked.
Does anyone know of a work around?

You could use the functions which are part of the ListView class:
smoothScrollByOffset(int offset);
or
smoothScrollToPosition(int position);
Or
if you want to scroll one by one you could use functions like:
private void scrollToNext() {
int currentPosition = getListView().getFirstVisiblePosition();
if (currentPosition == getListView().getCount() - 1)
return;
getListView().setSelection(currentPosition + 1);
getListView().clearFocus();
}
private void scrollToPrevious() {
int currentPosition = getListView().getFirstVisiblePosition();
if (currentPosition == 0)
return;
getListView().setSelection(currentPosition - 1);
getListView().clearFocus();
}

Continuously Auto-Scrolling ListView

I have a Listview in Android. I want that the Listview continuously scrolls from top to bottom by itself. It should happen infinitely
And obviously I want to capture the click on any of the items of the Listview, post that the scroll will continue
Anybody having experience with such an implementation. Please help !!

http://groups.google.com/group/android-developers/msg/753a317a8a0adf03
To scroll automatically, you can use this: listView.smoothScrollToPosition(position);
private void scrollMyListViewToBottom() {
myListView.post(new Runnable() {
#Override
public void run() {
// Select the last row so it will scroll into view...
listView.smoothScrollToPosition(myListAdapter.getCount() - 1);
// Just add something to scroll to the top ;-)
}
});
}