I've been having some trouble with onPause and onResume when implementing an ExpandableListView in my app. I may be doing this all wrong (in which case please tell me and I will endeavor to do it correctly) as I'm learning Android mainly from what I can find on the net. So, to jump into it, I've pretty much got my ExpandableListView working as I would like, but for one little bugbear. When I resume the activity (for example after the screen shuts off) I recreate my cursors (is that the best way to resume the activity? I was getting cursor errors before...) and then programatically expand the groups that were expanded when the activity was paused. Now ALL I want to do is change the background drawable for the expanded groups, but I can't seem to find a way to get their views. Any ideas?
#SuppressWarnings("unchecked")
#Override
protected void onResume() {
super.onResume();
String searchText = ((QueryString)this.getApplicationContext()).getQuery();
if((searchText == null || searchText.length() < 1))
if(!hasQuery)
refreshCursor();
else
searchCursor(queryString);
else
searchCursor(searchText);
ArrayList<Integer> ToExpand = (ArrayList<Integer>) ExpandedList.clone();
ExpandedList.clear();
for(Integer i : ToExpand)
{
listContent.expandGroup(i);
listContent.getChildAt(i).setBackground(getResources().getDrawable(R.drawable.listview_style_selected)); //NOT WORKING
}
}
EDIT:
What I really want is the View that I have just expanded programatically with listContent.expandGroup(i) so that I can then change the background drawable manually. Unfortunately getGroupView (where the background is normally changed) doesn't fire when you expand a group programatically so the background drawable remains unchanged. How can I get this view?
Call notifyDataSetChanged() in your adapter of your list. This should work. Maybe logging the "getChildAt" view helps.
I'm having a bit of trouble preserving the scroll position of a list view when changing it's adapter's data.
What I'm currently doing is to create a custom ArrayAdapter (with an overridden getView method) in the onCreate of a ListFragment, and then assign it to its list:
mListAdapter = new CustomListAdapter(getActivity());
mListAdapter.setNotifyOnChange(false);
setListAdapter(mListAdapter);
Then, when I receive new data from a loader that fetches everything periodically, I do this in its onLoadFinished callback:
mListAdapter.clear();
mListAdapter.addAll(data.items);
mListAdapter.notifyDataSetChanged();
The problem is, calling clear() resets the listview's scroll position. Removing that call preserves the position, but it obviously leaves the old items in the list.
What is the proper way to do this?
As you pointed out yourself, the call to 'clear()' causes the position to be reset to the top.
Fiddling with scroll-position, etc. is a bit of a hack to get this working.
If your CustomListAdapter subclasses from ArrayAdapter, this could be the issue:
The call to clear(), calls 'notifyDataSetChanged()'. You can prevent this:
mListAdapter.setNotifyOnChange(false); // Prevents 'clear()' from clearing/resetting the listview
mListAdapter.clear();
mListAdapter.addAll(data.items);
// note that a call to notifyDataSetChanged() implicitly sets the setNotifyOnChange back to 'true'!
// That's why the call 'setNotifyOnChange(false) should be called first every time (see call before 'clear()').
mListAdapter.notifyDataSetChanged();
I haven't tried this myself, but try it :)
Check out: Maintain/Save/Restore scroll position when returning to a ListView
Use this to save the position in the ListView before you call .clear(), .addAll(), and . notifyDataSetChanged().
int index = mList.getFirstVisiblePosition();
View v = mList.getChildAt(0);
int top = (v == null) ? 0 : v.getTop();
After updating the ListView adapter, the Listview's items will be changed and then set the new position:
mList.setSelectionFromTop(index, top);
Basically you can save you position and scroll back to it, save the ListView state or the entire application state.
Other helpful links:
Save Position:
How to save and restore ListView position in Android
Save State:
Android ListView y position
Regards,
Please let me know if this helps!
There is one more use-case I came across recently (Android 8.1) - caused by bug in Android code. If I use mouse-wheel to scroll list view - consecutive adapter.notifyDataSetChanged() resets scroll position to zero. Use this workaround until bug gets fixed in Android
listView.onTouchModeChanged(true); // workaround
adapter.notifyDataSetChanged();
More details is here: https://issuetracker.google.com/u/1/issues/130103876
In your Expandable/List Adapter, put this method
public void refresh(List<MyDataClass> dataList) {
mDataList.clear();
mDataList.addAll(events);
notifyDataSetChanged();
}
And from your activity, where you want to update the list, put this code
if (mDataListView.getAdapter() == null) {
MyDataAdapter myDataAdapter = new MyDataAdapter(mContext, dataList);
mDataListView.setAdapter(myDataAdapter);
} else {
((MyDataAdapter)mDataListView.getAdapter()).refresh(dataList);
}
In case of Expandable List View, you will use
mDataListView.getExpandableListAdapter() instead of
mDataListView.getAdapter()
This question has been asked a lot of times and I've systematically gone through each and tried to find which version of performItemClick works. Unfortunately I just can't get any of them to work despite my onclick method being called.
I have a listview with 5 items embedded into a fragment. This fragment is controlled by a fragmentstatepageradapter and a viewpager. I'm trying to restore the saved state.
lv.setAdapter(new SimpleAdapter(getActivity(), list,
R.layout.list_imageview, new String[] { "answer" },
new int[] { android.R.id.text1 }));
The simple adapter takes in a custom layout which has a textview and imageview within a layout. Initially the imageview is null and on click it is set to a tick or cross. This works when clicking the items myself just doesn't work programatically as follows:
#Override
public void onViewStateRestored(Bundle savedInstanceState) {
super.onViewStateRestored(savedInstanceState);
if (savedInstanceState != null) {
for (int i = 0; i < 5; i++) {
lv.performItemClick(lv.getAdapter().getView(i, null, null),
i, i);
Log.e("restoring state", "" + i);
}
}
}
I can confirm that onViewStateRestored is called and onItemClick is also called. I assume it's a problem in the way I'm performing the item click. I am currently just trying to get it work; I know I haven't yet checked which items have been clicked to selectively click them but that's an easy boolean[] away.
I thank you for your help, and sorry for such a simple question that's been repeated quite a few times; despite reading them I am still unable to get them to work.
I assume it's a problem in the way I'm performing the item click.
Right now you call performItemClick giving it a new View created by the getView method of the adapter. The problem is that if you setting the image is somehow related to the row view the onItemClick callback receives, you'll not see any results as that view is not related(it's "in the air") to the row view that is actually seen on the screen(or present in the ListView). But I'm just guessing.
Anyway, you shouldn't tie that ImageView work to the OnItemClickListener, you should implement it at the adapter level(and call notifydataSetChanged()), especially as you're trying to set multiple rows at once.
It's taken me quite a while to get my head around the Android Spinner. After several failed implementation attempts, and after reading many questions partially similar to my own but without satisfactory answers, and some without any answers at all, e.g. here and here, I finally get that a "spinner" in Android isn't meant to be the same thing as a "drop-down list" from desktop apps, or a select in HTML. However, what my app (and I'm guessing the apps of all the other posters whose questions are similar) needs is something that works like a drop-down box, not like a spinner.
My two problems are with what I first considered to be idiosynchrasies the OnItemSelectedListener (I've seen these as separate questions on this site but not as one):
An initial selection of the first list item is triggered automatically without the user's interaction.
When the item that was already selected is selected again by the user, it is ignored.
Now I realise that, when you think about it, it makes sense for this to happen on a spinner - it has to start with a default value selected, and you spin it only to change that value, not to "re-select" a value - the documentation actually says: "This callback is invoked only when the newly selected position is different from the previously selected position". And I've seen answers suggesting that you set up a flag to ignore the first automatic selection - I guess I could live with that if there's no other way.
But since what I really want is a drop-down list which behaves as a drop-down list should (and as users can and should expect), what I need is something like a Spinner that behaves like a drop-down, like a combo-box. I don't care about any automatic pre-selection (that should happen without triggering my listener), and I want to know about every selection, even if it's the same one as previously (after all, the user selected the same item again).
So... is there something in Android that can do that, or some workaround to make a Spinner behave like a drop-down list? If there is a question like this one on this site that I haven't found, and which has a satisfactory answer, please let me know (in which case I sincerely apologise for repeating the question).
+1 to David's answer. However, here's an implementation suggestion that does not involve copy-pasting code from the source (which, by the way, looks exactly the same as David posted in 2.3 as well):
#Override
void setSelectionInt(int position, boolean animate) {
mOldSelectedPosition = INVALID_POSITION;
super.setSelectionInt(position, animate);
}
This way you'll trick the parent method into thinking it's a new position every time.
Alternatively, you could try setting the position to invalid when the spinner is clicked and setting it back in onNothingSelected. This is not as nice, because the user will not see what item is selected while the dialog is up.
Ok, I think I've come up with a solution for my own situation with the help of both David's and Felix' answer (I believe David's helped Felix', which in turn helped mine). I thought I'd post it here together with a code sample in case someone else finds this approach useful as well. It also solves both of my problems (both the unwanted automatic selection and the desired re-selection trigger).
What I've done is added a "please select" dummy item as the first item in my list (initially just to get around the automatic selection problem so that I could ignore when it was selected without user interaction), and then, when another item is selected and I've handled the selection, I simply reset the spinner to the dummy item (which gets ignored). Come to think of it, I should've thought of this long ago before deciding to post my question on this site, but things are always more obvious in hindsight... and I found that writing my question actually helped me to think about what I wanted to achieve.
Obviously, if having a dummy item doesn't fit your situation, this might not be the ideal solution for you, but since what I wanted was to trigger an action when the user selected a value (and having the value remain selected is not required in my specific case), this works just fine. I'll try to add a simplified code example (may not compile as is, I've ripped out a few bits from my working code and renamed things before pasting, but hopefully you'll get the idea) below.
First, the list activity (in my case) containing the spinner, let's call it MyListActivity:
public class MyListActivity extends ListActivity {
private Spinner mySpinner;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// TODO: other code as required...
mySpinner = (Spinner) findViewById(R.id.mySpinner);
mySpinner.setAdapter(new MySpinnerAdapter(this));
mySpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> aParentView,
View aView, int aPosition, long anId) {
if (aPosition == 0) {
Log.d(getClass().getName(), "Ignoring selection of dummy list item...");
} else {
Log.d(getClass().getName(), "Handling selection of actual list item...");
// TODO: insert code to handle selection
resetSelection();
}
}
#Override
public void onNothingSelected(AdapterView<?> anAdapterView) {
// do nothing
}
});
}
/**
* Reset the filter spinner selection to 0 - which is ignored in
* onItemSelected() - so that a subsequent selection of another item is
* triggered, regardless of whether it's the same item that was selected
* previously.
*/
protected void resetSelection() {
Log.d(getClass().getName(), "Resetting selection to 0 (i.e. 'please select' item).");
mySpinner.setSelection(0);
}
}
And the spinner adapter code could look something like this (could in fact be an inner class in the above list activity if you prefer):
public class MySpinnerAdapter extends BaseAdapter implements SpinnerAdapter {
private List<MyListItem> items; // replace MyListItem with your model object type
private Context context;
public MySpinnerAdapter(Context aContext) {
context = aContext;
items = new ArrayList<MyListItem>();
items.add(null); // add first dummy item - selection of this will be ignored
// TODO: add other items;
}
#Override
public int getCount() {
return items.size();
}
#Override
public Object getItem(int aPosition) {
return items.get(aPosition);
}
#Override
public long getItemId(int aPosition) {
return aPosition;
}
#Override
public View getView(int aPosition, View aView, ViewGroup aParent) {
TextView text = new TextView(context);
if (aPosition == 0) {
text.setText("-- Please select --"); // text for first dummy item
} else {
text.setText(items.get(aPosition).toString());
// or use whatever model attribute you'd like displayed instead of toString()
}
return text;
}
}
I guess (haven't tried this) the same effect could be achieved using setSelected(false) instead of setSelection(0), but re-setting to "please select" suits my purposes fine. And, "look, Ma, no flag!" (Although I guess ignoring 0 selections is not that dissimilar.)
Hopefully, this can help someone else out there with a similar use case. :-) For other use cases, Felix' answer may be more suitable (thanks Felix!).
Look. I don't know if this will help you, but since you seem tired of looking for an answer without much success, this idea may help you, who knows...
The Spinner class is derived from AbsSpinner. Inside this, there is this method:
void setSelectionInt(int position, boolean animate) {
if (position != mOldSelectedPosition) {
mBlockLayoutRequests = true;
int delta = position - mSelectedPosition;
setNextSelectedPositionInt(position);
layout(delta, animate);
mBlockLayoutRequests = false;
}
}
This is AFAIK taken from 1.5 source. Perhaps you could check that source, see how Spinner/AbsSpinner works, and maybe extend that class just enough to catch the proper method and not check if position != mOldSelectedPosition.
I mean... that's a huge "maybe" with a lot of "ifs" (android versioning comes to mind etc.), but since you seem frustrated (and I've been there with Android many times), maybe this can give you some "light". And I assume that there are no other obvious answers by looking at your previous research.
I wish you good luck!
Here is an alternative solution to differentiate between any (intended or unintended) programmatic and user-initiated changes:
Create your listener for the spinner as both an OnTouchListener and OnItemSelectedListener
public class SpinnerInteractionListener implements AdapterView.OnItemSelectedListener, View.OnTouchListener {
boolean userSelect = false;
#Override
public boolean onTouch(View v, MotionEvent event) {
userSelect = true;
return false;
}
#Override
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
if (userSelect) {
// Your selection handling code here
userSelect = false;
}
}
}
Add the listener to the spinner registering for both event types
SpinnerInteractionListener listener = new SpinnerInteractionListener();
mSpinnerView.setOnTouchListener(listener);
mSpinnerView.setOnItemSelectedListener(listener);
This wouldn't handle the case in which the re-selection of the same item by the user doesn't trigger the onItemSelected method (which I have not observed), but I guess that could be handled by adding some code to the onTouch method.
Anyway, the problems Amos pointed out were driving me crazy before thinking of this solution, so I thought I'd share as widely as possible. There are many threads that discuss this, but I've only seen one other solution so far that is similar to this: https://stackoverflow.com/a/25070696/4556980.
Modifying the Spinner is useful if you want to have multiple selections simultaneously in the same activity.
If you only desire the user to have a hierarchical selection, for example:
What do you want to eat?
Fruit
Apples
Bananas
Oranges
Fast Food
Burgers
Fries
Hot dogs,
then the ExpandableListView might be better for you. It allows the user to navigate a hierarchy of different groups and choose a child element. This would be similar to having several Spinners for the user to choose from - if you do not desire a simultaneous selection, that is.
I worked through several of the issues mentioned in this thread before I realized that the PopupMenu widget is what I really wanted. That was easy to implement without the hacks and workarounds needed to change the functionality of a Spinner. PopupMenu was relatively new when this thread was started in 2011, but I hope this helps someone searching for similar functionality now.
I'm now developing an application that uses a ListView with a
CheckedTextView on every item that managed by an ArrayAdapter to
support multiple chooses. The contents in my ListView are dynamic, that
means, can be changed during runtime. Now I try to use
ListView.getCheckedItemPositions() to get all checked items, Because I want
to save all the checked positions and auto-check them when user go back to
this page again. So I need to save checked results for every page.
For the first page everything works fine as expected. But when user goes to
another page and make some chooses, the result array that ListView returned
contains some positions that are never checked. I don't why ListView has
this strange behavior. Even for a page that in fact no checked happens but
ListView gives me a result that indicates there's one item has been checked.
could anyone who can teach me how to get the position of CheckedTextView
in its OnClickListener callback?
example code is appreciate.
Thanks in advance...
The listview recycles its views so when you go to a different page and then return to the previous page, the listview recalls the getView() function for its views. To make sure that the order of the checked views are not mixed up, create an arraylist that contains the check state of all the views before initializing the adapter. Then pass the arraylist as an argument for the adapter's constructor. There, in the getView() function, set the checked state of each checkable textview based on the arraylist. Then, return to the activity class and override the onItemClick() event. Using the view that is given to you when the function is called, do the following to get the checkable textview and set its checked state:
listView1.setOnItemClickListener(new OnItemClickListener()
{
#Override
public void onItemClick(AdapterView<?> arg0, View selectedView, int position , long id)
{
CheckedTextView tv = (CheckedTextView)selectedView.findViewById(R.id.textview);
if (tv.isChecked())
{
tv.setChecked(false);
checkStatesOfViews.get(position) = false;
}
else
{
tv.setChecked(true);
checkStatesOfViews.get(position) = true;
}
}
});