I've got a GridView with a custom Adapter, displaying thumbnails of pictures to the user. I can select and deselect pictures (I use setAlpha(0.25) on the views to notify the user of the change), and that's all well and fine.
Now what I want to do next, is have a button on top of the gridview that clears the whole selection, i.e. call setAlpha(1.0) on all views that were changed. So far I can reset my elements in the adapter, and I can setAlpha to 1, but the view doesn't update unless I scroll it out of the display, and then get back to it, or notify the adapter of changes, which redraws all my views, which does not look too pretty if only one element was selected.
I already dynamically set and reset individual elements through the GridView's onClickListener, but can't do this for more. I even tried calling performClick on all selected items through my button, but again it only displays the changes after the views have been out of the screen and are shown again.
Here's how I simulate the clicks:
for (int i = 0; i < mAdapter.getCount(); i++) {
PictureForSelection tempPic = (PictureForSelection) mAdapter.getItem(i);
if (tempPic.isPicSelected()) {
//tempPic.setIfSelected(false);
gridview.performItemClick(mAdapter.getView(i, null, null), i, i);
}
}
EDIT:
Conclusion - don't simulate clicks like this :)
So now I skip click simulation and use this:
gridview.getChildAt(i).setAlpha((float) 1.0);
In general it does exactly what I wanted it to do, except for one case:
If I have for example 3 pictures selected, one is off screen, one is partly shown, and one is fully shown, the ones shown (even partially) don't update their views.
If all the selected pictures are displayed it works flawlessly, but if some are out of the display, the rest do not update until the adapter's getView() gets called by Android. Still, thanks #mmlooloo for getting me so far.
If anyone knows a way around this, please do share :)
After setting your alpha you can call imageview.invalidate(); this causes your imageview to redraw itself.
if notifyDataSetChanged() is not working you can try like this.
i'm not sure whether this works,
1.onclick of the button you set the gridView.setAdapter(null);
2. Then set a new CustomAdapter object to gridview with default values.
Related
I have a simple horizontal recyclerview. As the user scrolls, the current item looses focus has background set to transparent and the new focused item is to have its background color changed to green. I have a simple method that takes in the focused position, changes it's color and sets the reset of the items to transparent.
public void resetRecycleColor(int rowindex){
for(int i=0; i < mRecyclerView.getAdapter().getItemCount(); i++){
if(i== this.rowindex){
Log.v("SCROLLS ", "COLOR GREEN "+ i);
mRecyclerView.getLayoutManager().findViewByPosition(i).setBackgroundColor(Color.GREEN);
}else{
Log.v("SCROLLS ", "COLOR TRANSPARENT "+i );
mRecyclerView.getLayoutManager().findViewByPosition(i).setBackgroundResource(R.color.gridBackgroundBlack);
}
}
}
Am I attempting to change the item background correctly? Something is wrong because it crashes on the line where the color is set. Comment out those lines and scrolling works fine. Can somebody point out why the crash may occur?
Thanks
You don't seem to understand the ViewHolder pattern.
You only have enough views (plus about 2) to fill RecyclerView. For example if you have 2000 items but they are represented in list that shows 3 items each, you only have 5 ViewHolders created. That way when scrolling views that exit the screen, reenter from the other side but displayed values are changed (in OnBindViewHolder).
Crash is occurring in findViewByPosition(i) since you're trying to get views for entire list but you only have views for a few of them, so this returns null.
I don't understand your use case entirely, but if you're repeatedly calling your method during onScroll then it has really bad performance, cleaner solution would be modifying your adapters onBindViewHolder to properly modify focused view and calling notifyItemChanged() to trigger rebinds on new/old focused view.
I have a layout that consists of 3 contiguous ListViews. Selecting an item in the left most list will start the second list, and so on. I am trying to begin the fragment with the first item in the left most list selected, and because a lot of logic is required, I am attempting to trigger on click instead of redo-ing all the logic. I am using this:
mListView.performItemClick(mListView, 0, mListView.getItemIdAtPosition(0));
Is what I am attempting possible? and if it is, where do I call this?
ANSWER:
So it seems that the reason this wasn't working for me is because I was manually highlighting a View within the row View and it wasn't instantiated yet (or something like that).
I used this code to call it after the ListView was laid out:
mListView.post(new Runnable() {
#Override
public void run() {
mListView.performItemClick(mListView, 0, mListView.getItemIdAtPosition(0));
}
});
EDIT:
I have 4 lists that depend on data being sent from the previous ones before being instantiated, and for some strange reason, this runnable method only works for the first list. For the others, I used this answer: https://stackoverflow.com/a/15399035/1549672. Also, strangely enough, this does not work on the first list. All the lists are nearly identical.
As per earlier comment:
You can try wrapping the selection change in a Runnable and post that to the ListView. That way the selection change will not happen until the ListView (and its children) has been measured and laid out etc. Do make sure you set the adapter before attempting to change the selection.
I need all of the other views in my arrayadapter to check their attributes and return to a default attribute at certain times
use case: listview items (a)(b)(c)(d) , when you touch (a) it's background turns black. This is done in the ontouchListener. But when you touch view (b) it's background turns black BUT (a)'s needs to turn back to the default which is not black
I dabbled around with recalling the arrayadapter at the end of the view.OnClickListener but the problem with this is that it also resets the scroll position of the view, so if this list was much longer - which it is - and user touched item (r) , then it would reset the list and put the user back at item (a) at the top
I was looking at notifydatasetchangedbut I am not sure how to use that and where it should work
insight appreciated
notifyDataSetChanged will do the job. You can call that at any time in your code and this will trigger the adapter to call getView for the visible list items again and so update their content. So basically the only thing you have to do is to update the list item states or information before calling that method.
BACKGROUND:
I have a grid of 36 buttons, lets say a 6 rows & 6 columns numbered 1 to 36, displayed 2 rows at a time via a GridView and custom Adapter
The grid displays fine, and all of the scrolling works properly.
QUESTION:
I want to be able to click on an item, have it removed from the grid and the remain items shuffle up into place. Currently I am able to disable the item disabled, set its visibility to INVISIBLE or GONE, but none of these will actually remove it from the display.
Suggestions?
Specifically, you need to remove the corresponding object from the data set of the underlying adapter and then call adapter.notifyDataSetChanged(). This isn't going to provide you with an animation, though, if that was part of this question.
It may be interesting to try a tween animation for the item in question and then finally remove it from your adapter at the end. I'm not well-versed in animation, so I'm not sure how well this will work in an AdapterView.
You should be able to update the adapter, and then call notifyDataSetChanged to force the grid view to be updated.
I have an android-app with a listview in an activity. The listview has, if I call it so, three data states.
no data loaded from inet -> only one dummy item is visible, saying that data is loading;
data is loaded and shown in list;
one listitem is clicked and now shows more information for this listitem (so it is increased in its height).
On every state change (1 -> 2, 2 -> 3), I call notifyDataSetChanged() on this ListAdapater.
This causes the listview to scroll down to the last item. This is ugly in the first transition and even more ugly in the second because the clicked list item is now out of focus.
As I can see, this happens with a google g1 with android 1.6. An htc touch with the same sdk acts like desired (I will try to figure it out with some more devices).
To avoid this, I tried to read out getScrollY() and set this value back. but this returns 0. The reason for this return value I already found on stackoverflow in other questions.
Has anyone else seen this problem? Why does the listview scroll to the last item? It was mentioned that listview keeps track of the scroll position. but it seems that it does not in my case.
Or maybe I am calling the wrong refresh method? Is notifyDataSetChanged the correct one?
I believe you want:
listview.setTranscriptMode(ListView.TRANSCRIPT_MODE_DISABLED);