Android : Using A ListView - An Adapter - How To Use Notify Data Set Changed()
Jun 3, 2010
Just watched Google IO's "World Of ListView" presentation [1]. Awesome stuff. I think every Android dev should watch it.
One gotcha for me was to use BaseAdapter.notifyDataSetChanged[2]. I checked code that I have written more than a year ago and found that I did try to use that, but commented it out with '// doesn't work' and I use requery() instead. That is of course much slower.
I now tried to find out why I wrote that it didn't work and hoped that I am meanwhile so much wiser that it would be easier to understand the proper use of the API. So much for ambition: The effect I see is that the list is not updated after I call notifyDataSetChanged(), but works with requery() and I am not so much wiser.
What could be the issue here? I use a ResourceCursorAdapter and only implemented the bindView() Method. This method is called when I call notifyDataSetChanged() on the RCAdapter. However the method is called with a cursor that contains the stale data.
Now there was a second gotcha from the presentation that I couldn't really place. It was said that the data should be committed on the GUI thread too (before calling notifyDataSetChanged()). I couldn't place it then, but I now suspect that this may be the issue here. So the rule would be to do the commit() on the Cursor on the UI thread? I do the updates to the database using a Service. This Service runs in the background, sometimes the app is in the foreground at the same time, but most often not. So I don't see how I should commit something in a UI thread? Is this the issue here? There are two different Cursors and I could only use notifyDataSetChanged when it would be the same cursor, otherwise requery() is correct?
Is that it? Any ideas? Is somebody going to write a book "The Android SDK - The missing manual"?
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Nov 21, 2010
I have a list view that can display items based on internal state (it has items, and 'viewed' items). i need to be able to toggle between the two states, i do that using a simple button that change the adapter's state and the adapter then called notifyDatasetChanged(). My data DOES gets updated, however i was facing two problems:
if in the previous mode the list was partially scrolled, it stayed in that state after i changed the data set (if i was half the way down i'll be half way down in the new data set as well, this is not the behavior i want, but i cols not find a way to scroll the list manually to position 0. any ideas?
(setSelected is not exactly a solution since i DON'T want any selection i want to stay in touch mode) In my list View each item has an image that is fetched from the net, as so it's being brought using my networking manager and i send the image request ONLY if i'm in this screen for the first time OR if scroll state is idlle, i didn't want to start loading images from the getView method since if i fling the screen it may load a lot of unnecessary images. However when calling notifyDatasetChanged() the scroll listener methods are not called. i solved this one by using notifyDatasetInvalidated even though my data is not empty, is there a better way to solve this issue ?
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Nov 21, 2010
I have a list view that can display items based on internal state (it has items, and 'viewed' items). i need to be able to toggle between by two states, i do that using a simple button that change the adapter's state and the adapter then called notifyDatasetChanged(). My data DOES gets updated,
However i was facing two problems:
1. if in the previous mode the list was partially scrolled, it stayed in that state after i changed the data set (if i was half the way down i'll be half way down in the new data set as well, this is not the behavior i want, but i cols not find a way to scroll the list manually to position 0. any ideas ?
2. In my list View each item has an image that is fetched from the net, as so it's being brought using my networking manager and i send the image request ONLY if i'm in this screen for the first time OR if scroll state is idlle, i didn't want to start loading images from the getView method since if i fling the screen it may load a lot of unnecessary images. However when calling notifyDatasetChanged() the scroll listener methods are not called. i solved this one by using notifyDatasetInvalidated even though my data is not empty, is there a better way to solve this issue ?
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Feb 27, 2010
I have a list which is filled with a custom Array Adapter. I want to upload a progress bar every second, so i try to use notifyDataSetChanged in order to repaint the list but it doesn't seem to work.
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Jul 1, 2010
I'm trying to clean up some code and now I'm determined to get this seemless ListView updating working...
I want my ListView to be updated when I call notifyDataSetChanged() but nothing happens... I'm also passing the autoRequery flag to true when creating my CursorAdapter.
Cursor c = FavoritesHandler.getCategoryFavorites(getSQLiteInstance(), category); m_favoriteAdapter.changeCursor(c); startManagingCursor(c);
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Nov 4, 2010
I have ListView with adapter class which extends ArrayAdapter and implements SectionIndexer. The problem is section indexer is not updated when adapter data is changed. Even if i add new elements the section remain the same. I tried some options setFaseScrollEnabled(false); setFaseScrollEnabled(true); but i got IndexOutOfBounds exception. So how can i update sectionIndexer when adapter's data is changed.
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Aug 10, 2010
I must be missing something simple here.I've searched around but don't think my search query is touching on the right topics to yield results. Anyhow, what I'm after is running through the array of data I bind to a ListView after a "Submit" button has been clicked.
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Sep 3, 2010
I have a ListView populated via a CursorAdapter. I give my user the ability to alter the data in the list. For example, the user can mark a row as being unread (the data are messages).
Suppose my user marked a row unread. Would a proper implementation mark the row in the database as read and then requery the Cursor?
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Jan 13, 2010
I'm trying to make my first widget that toggles the screen time out settings. Is there a way for the widget to be notified when Settings.System.SCREEN_OFF_TIMEOUT has been changed? I would like to know this so I can update the widget graphic accordingly.
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May 4, 2009
I have a ListView whose position should be changed automatically along with the data. So, when the adapter's data has changed (adapter is calling notifyDataSetInvalidated), I'm calling setSelection. This has no effect. If the call to setSelection is done later (e.g. in a click handler) it is working.
The second problem is, that the ListView maintains the scroll position of the list although the data is completely invalidated, that makes no sense IMO.
It looks like a call to layoutChildren before the call to setSelection does help in this case, but layoutChildren is protected.
What is the correct way to do this?
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May 18, 2009
I have ListActivity to show a custom list. The adapter for this list is a complex layout only known for each row at runtime depending on data gathered in a previous activity. The question I have is simple. I know it takes 4-6 seconds to prepare the adapter for the rows that will be visible (first 10), however I would like to let the user know by means of the empty list functionality or otherwise. At present the ListActivity is launched via a button on a previous activity and when that button is clicked the new activity will not be loaded until the adapter is completed, and the user is stuck with the previous activity until this happens. Code...
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Jan 7, 2010
In a ListView/CursorAdapter, it is easy to go from a position to an itemId
CODE:..........
Is there any way to do the reverse mapping? From an itemId, get its position in the list?
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Mar 30, 2010
I've implemented a custom ListView and Adapter, and sometimes I receive IllegalStateException exception:" ERROR/AndroidRuntime(3575): java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread."
Here is some code example: Code...
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Aug 4, 2010
I have a listview with a custom arrayadapter that handles about 15 strings. The style of each row alternates (between labels and values for those labels--for example row 1 could be "email address" and row 2 would be the actual email address). I'm changing the style of each row to alternate like this in the arrayadapter's getView() method. So if the item at the current position is a label, I'll change the styling from the default row style (which is what the values have applied to them). When the listview first loads, the styling is perfect and just how I want it to be. If I scroll the list slowly up or down, it stays that way. However, if I scroll the list fast up and down, the styling of the value rows starts changing to that of the label ones until all of the rows have the styling of a label row. I've used custom adapters on other listviews in the app with no problems like this. Found out that it also changes all of the rows to the label styling on portrait->landscape orientation changes. Doesn't do this on landscape->portrait changes. Below is the adapter I'm using.
public class DetailsAdapter extends ArrayAdapter<String> { private TextView text = null; private String item = null;
public DetailsAdapter(Context context, int resource, int textViewResourceId, String[] objects) { super(context, resource, textViewResourceId, objects);
} @Override public View getView(int position, View convertView, ViewGroup parent) { text = (TextView) super.getView(position, convertView, parent); item = getItem(position);
if (item.equals("Name") || item.equals("Mobile") || item.equals("Home") || item.equals("Email") || item.equals("Address")) { text.setBackgroundColor(0xFF575757); text.setTextSize(15);
text.setTypeface(null, Typeface.BOLD); text.setPadding(8, 5, 0, 5);
} else { text.setPadding(15, 15, 0, 15); } return text;
} @Override public boolean isEnabled(int position) { item = getItem(position);
if (item.equals("Name") || item.equals("Mobile") || item.equals("Home") || item.equals("Email") || item.equals("Address")) { return false;
} else { return true; } } }
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Jul 1, 2010
I'm making a custom adapter so that I can display a list of items with icons which looks like the menu that comes up when you long click the home screen. For some reason though the list items are not clickable. The can be navigated to with the D-pad but they cannot be clicked in any way. I thought maybe the problem was with the AlertDialog I was using so I replaced a working adapter I had elsewhere but I have the same issue there. My adapter looks like this:
ArrayList<IconListItem> mItems; LayoutInflater mInflater;
public IconListAdapter(Context context, ArrayList<IconListItem> items) {
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mItems = items;
} public IconListAdapter(Context context) {
this(context, new ArrayList<IconListItem>());
} public void add(IconListItem item) { mItems.add(item);
notifyDataSetChanged(); return item;
} public void remove(IconListItem item) { mItems.remove(item); notifyDataSetChanged();
} @Override public int getCount() { return mItems.size();
} @Override public IconListItem getItem(int position) { return mItems.get(position);
} @Override public long getItemId(int position) { return position;
} @Override public View getView(int position, View convertView, ViewGroup parent) { View view;
if(convertView == null){ view = mInflater.inflate(R.layout.two_line_icon_list_item, null);
} else { view = convertView; } IconListItem item = mItems.get(position);
TextView lineOne = (TextView) view.findViewById(R.id.firstLine);
TextView lineTwo = (TextView) view.findViewById(R.id.secondLine);
ImageView iconImage = (ImageView) view.findViewById(R.id.icon);
lineOne.setVisibility(View.VISIBLE); lineTwo.setVisibility(View.VISIBLE);
iconImage.setVisibility(View.VISIBLE); lineOne.setText(item.getText());
if (item.getSubtext() == null) lineTwo.setVisibility(View.GONE);
else lineTwo.setText(item.getSubtext());
if (item.getIcon() == null) iconImage.setVisibility(View.GONE);
else iconImage.setImageDrawable(item.getIcon());
return view; }
And the XML it's inflating:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="6dip" >
<ImageView android:id="@+id/icon" android:layout_width="wrap_content"
android:layout_height="fill_parent" android:layout_marginRight="6dip" />
<LinearLayout android:orientation="vertical" android:layout_width="wrap_content"
android:layout_weight="1" android:layout_height="fill_parent" >
<TextView android:layout_width="fill_parent" android:layout_height="wrap_content"
android:layout_weight="1"android:gravity="center_vertical"
android:id="@+id/firstLine" android:ellipsize="marquee" android:inputType="text" />
<TextView android:layout_width="wrap_content" android:layout_height="0dip"
android:layout_weight="1" android:ellipsize="marquee"
android:id="@+id/secondLine" android:inputType="text" />
</LinearLayout> </LinearLayout>
When I say they are not clickable, I mean that they items do not highlight in orange when I press them nor does onItemClick ever get called. In my code I have this, a different adapter for another purpose and it works perfectly
this.foos= foos; fa = new FooAdapter(this.foos); fooList.setAdapter(fa);
// View the details for an item when it is selected
fooList.setOnItemClickListener(new OnItemClickListener() {
@Override public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
Intent i = new Intent(MyActivity.this, MyOtherActivity.class);
i.putExtra("foo", ((fooAdapter)arg0.getAdapter()).getItem(arg2));
i.putExtra("list_position", arg2);
MyActivity.this.startActivityForResult(i, 0);
} } );
But when I swap out the first 3 lines for
IconListAdapter ila = new IconListAdapter(this);
ila.add(0, "Test 1", android.R.drawable.ic_menu_mylocation);
ila.add(0, "Test 2", android.R.drawable.ic_menu_edit);
ila.add(0, "Test 3", android.R.drawable.ic_menu_search);
groupList.setAdapter(ila);
I t stops working.
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Nov 1, 2010
I have a listView using a custom adapter. Each row contains a button and some other Views. I want to be able to click either on the button, or on the row itself (to edit the item of the list that is clicked).
Setting an onItemClickListener in the activity won't work because of this problem
I think I have to set an onClickListener in the getView() method of my adapter for it to work properly.
I would like to use my activity's onClickListener, in order to use a startActivityForResult() when the row is clicked, in order to have something returned to my activity when the item edition activity is over.
How can I do that?
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Aug 30, 2012
i've been trying to get this to work... but it isnt working.
there was no Exception to catch, the app just crash.
Code:
public class MainActivity extends Activity{
...
private void loadFromFile_populateListView(final String data){
[code].....
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Aug 29, 2010
Im using ListView to to show some custom data, once data is updated in the adapter i call notifyDatasetChanged(), so the view will get updated, all of this works well, my issue though is i would like to run an animation once only on items that got changed when the adapter was updated. currently i keep a copy of all the changed objects and i tried to animate the correct items through the getView() call.
However if i do it only once for every getView call then i see no animation most of the time on items that changed. if i continue to do so in successive getView calls i see animation on items that don not change as well and also the ones that changed get animated again and again.
Im guessing sometimes android calls the getView() for other reasons than showing the generated view immediately, and thats the reason it doesnt work if i do it once.
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Jul 3, 2010
I'd like to make a list adapter that formats views like this:
I want to be able to fire a different onClick when the user clicks the image. I have defined the onClick on the image itself in the getView() override, but how do I then get the position of the line that was clicked so I can update the record in the database to record the action?
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Jan 12, 2010
I have the following code to intantiate a SimpleCursorAdapter to use with a ListView. As you can see I have passed the R.layout.log_item to display the list items, and one value/control to bind to (TripDate).
SimpleCursorAdapter sca = new SimpleCursorAdapter(this, R.layout.log_item,c,new String[] {DBAdapter.KEY_LOG_TRIPDATE},new int[]{R.id.txtTripDate});
This works. I currently only have one widget in the layout xml, a TextView to hold the TripDate.
How do I pass multiple binding parameters for the additional widgets in the layout? So I can also display other info.
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Mar 9, 2010
I cant find a way to save the checkbox state when using a Cursor adapter. Everything else works fine but if i click on a checkbox it is repeated when it is recycled. Ive seen examples using array adapters but because of my lack of experience im finding it hard to translate it into using a cursor adapter. Could someone give me an example of how to go about it.code...
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Nov 16, 2010
How to use a layout as empty view for a listview when the adapter has zero elements?
setEmptyView is not working with this code :
CODE:..............
Layouts used :
CODE:...........
main.xml
CODE:...............
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Nov 24, 2010
I have written a TestSuite to find out how to calculate the rotation angles from the data you get in SensorEventListener.onSensorChanged(). I really hope you can complete my solution to help people who will have the same problems like me. Here is the code, i think you will understand it after reading it. Feel free to change it, the main idea was to implement several methods to send the orientation angles to the opengl view or any other target which would need it. method 1 to 4 are working, they are directly sending the rotationMatrix to the OpenGl view. method 6 works now too, but i have no explanation why the rotation has to be done y x z.. all other methods are not working or buggy and i hope someone knows to get them working. i think the best method would be method 5 if it would work, because it would be the easiest to understand but i'm not sure how efficient it is. the complete code isn't optimized so i recommend to not use it as it is in your project. Code...
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Apr 25, 2010
I'm running into an IllegalStateException updating an underlying List to an Adapter (might be an ArrayAdapter or an extension of BaseAdapter, I don't remember). I do not have or remember the text of the exception at the moment, but it says something to the effect of the List's content changing without the Adapter having been notified of the change.This List /may/ be updated from another thread other than the UI thread (main). After I update this list (adding an item), I call notifyDataSetChanged. The issue seems to be that the Adapter, or ListView attached to the Adapter attempts to update itself before this method is invoked. When this happens, the IllegalStateException is thrown.If I set the ListView's visibility to GONE before the update, then VISIBLE again, no error occurs. But this isn't always practical.I read somewhere that you cannot modify the underlying this from another thread--this would seem to limit an MVC pattern, as with this particular List, I want to add items from different threads. I assumed that as long as I called notifyDataSetChanged() I'd be safe--that the Adapter didn't revisit the underlying List until this method was invoked but this doesn't seem to be the case.
I suppose what I'm asking is, can it be safe to update the underlying List from threads other than the UI? Additionally, if I want to modify the data within an Adapter, do I modify the underlying List or the Adapter itself (via its add(), etc. methods). Modifying the data through the Adapter seems wrong.I came across a thread on another site from someone who seems to be having a similar problem to mine: http://osdir.com/ml/Android-Developers/2010-04/msg01199.html (this is from where I grabbed the Visibility.GONE and .VISIBLE idea).To give you a better idea of my particular problem, I'll describe a bit of how my List, Adapter, etc. are set up.I've an object named Queue that contains a LinkedList. Queue extends Observable, and when things are added to its internal list through its methods, I call setChanged() and notifyListeners(). This Queue object can have items added or removed from any number of threads.I have a single "queue view" Activity that contains an Adapter. This Activity, in its onCreate() method, registers an Observer listener to my Queue object. In the Observer's update() method I call notifyDataSetChanged() on the Adapter.I added a lot of log output and determined that when this IllegalStateExcption occurs that my Observer callback was never invoked. So it's as if the Adapter noticed the List's change before the Observer had a chance to notify its Observers, and call my method to notify the Adapter that the contents had changed.
So I suppose what I'm asking is, is this a good way to rig-up an Adapter? Is this a problem because I'm updating the Adapter's contents from a thread other than the UI thread? If this is the case, I may have a solution in mind (give the Queue object a Handler to the UI thread when it's created, and make all List modifications using that Handler, but this seems improper).I realize that this is a very open-ended post, but I'm a bit lost on this and would appreciate any comments on what I've written.
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Oct 2, 2009
How to load data in expandable List Adapter through Scroll .
Means I want to add data as per Scrolling in Run time.
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May 26, 2010
I have implemented Section Indexer for an Adapter class which extends BaseAdapter.Now for the first launch Section Indexer is showing an overlay correctly. But when the contents of the list gets updated the Section Overlay does not get updated and gives ArrayOutOfBoundException. Now what happens is overlay gets updated but the Overlay is coming to the left top of the listview.
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Jun 18, 2010
I have seen examples implementing a custom Filter. The Android developer docs talk about implementing a Filterable interface. Does anyone have any advice and/or sample code on the best way to implement filtering in a ListView ?
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May 24, 2010
After months of being really happy with 1.5, I ran with OTA 2.1 for about a week.... hated it! While I didn't see any outright bugs, the phone had hugely sluggish response, very poor battery life, etc. Finally decided to to the Factory Data Reset this morning, and voila - lovin' my Eris again.
Things to note:
Before Factory Data reset w/ 2.1 OTA:
- Phone uptime and awake time were almost equal (not good)
- Had the 50% without signal message
- 'Android System' always listed as top user of battery usage (60-70%)
- Even while idle, phone always felt 'warm' (like it was continually running a background process, as evidence by poor battery life)
After Factory Data reset w/ 2.1 OTA:
- Phone uptime and awake time now as expected (awaketime < uptime)
- No more 50% signal message
- Cell Standby and Phone Idle now top users of batter usage.
- Phone now cool to the touch while idle
One thing to note is even after the reset, I still had issues syncing Gmail contacts, and needed to delete the contacts cache.
While I won't conjecture about root cause, I'm hoping Google and VZ learn from this experience, as much of this mucking about is *way* beyond what most 'normal' users would put up with. My wife loves her iPhone and just laughs at me dealing with all this c**p. Besides, I can't remember the last time *she* had to reboot her phone..
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Aug 14, 2010
I am generating the random numbers and do some functionality with that .but when i change the orientation new random numbers are coming.But I want portrait random numbers.For this give me some suggestions.
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Oct 28, 2010
I'm have a custom GridView Array Adapter. The problem for me is that when the grid list gets large enough to scroll off the screen the gridview and arraylist get out of sync. For instance in my case I have code that checks if an actor is of type director the text color should be red. if you scroll up and down my list enough times all the actors text in my gridview will become red. The thing is that the Gridview appearance actually looks fine its the backing data. Here is the complete class. In the code you can see where I tried to override getItem and getItemId but that didn't fix anything. Code...
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