I'm working with the newest Android SDK and I want to filter my ListView which represents a list of different plants, with CheckBoxes.
In my list I have 800 Items with different attributes (e.g. color, size, edibility), and the CheckBoxes should filter the list in a subtractive way. Only the list items/views which match all attributes should be visible - all other rows should be invisible(the program should work like the filtering system on www.pilzsuchmaschine.de).
I tried to modify the getView() of my custom ArrayAdapter but I didn't get the right idea how to do that properly. Does anyone have a solution?
My ArrayAdapter is pretty the same as this one.
I tried to modify the getView() of my custom ArrayAdapter but I didn't
get the right idea how to do that properly. Does anyone have a
solution?
You don't do the filtering in the getView() method. First set a OnCheckedChangeListener on all the filter CheckBoxes to monitor their status(each of those CheckBoxes should have a boolean variable to hold its status). When a filter CheckBox is checked/unchecked update the status variable and then filter the ListView. Filtering the ListView can be done in two ways, manually or by using the dedicated mechanism(the Filter class).
Manually, when the user checks a CheckBox you'll take all the statuses of the filter CheckBoxes and match them against each element of the list of plants. Which element matches all the CheckBoxes statuses is valid and should be added to a new list. After this is done, make the adapter point to the newly created list and call notifyDataSetChanged(). I wouldn't go with this approach as you have a lot of items.
The proper way would be to make your own adapter along with its Filter method(in this case the adapter will hold the statuses of the filter CheckBoxes). When the user checks a filter CheckBox call a method on the adapter to update the corresponding boolean status. Also call the getFilter() method on the adapter and do the filtering: ((Filterable) adapter).getFilter().filter(null). There are a lot of tutorials there about implementing a Filter for an adapter.
Related
I want to make a diable switch that can instantly gray out and disable a list of options from a listView, but I am not sure how to acchieve this with a CustomAdapter for each single row. With only textview it should be easy to set it with a onclick method, but can I also do that with a CustomAdapter?
Your question is kind of abstract because it doesn't have any code samples and no specific problem as well. So my answer will be abstract as well.
To achieve this set a listener on your switch. Once it's clicked, update the model that is used for displaying your adapter items.
If you need to update all items in the list, then you can add a boolean variable to the adapter class. Use this variable in your getView() method to decide whether the item should be grayed out or not. When the value is changed, call notifyDataSetChanged() on the adapter object. It will trigger redrawing all items in the list.
If you need to update only specific items, then add this boolean variable to the item model itself. Iterate over collection and set this flag where needed. All other logic is the same - use this variable in getView() and call notifyDataSetChanged().
I am trying to better understand the internal functioning of ListView as it pertains to selecting one or multiple items- it's actually amazing how difficult it was for me to even get this far in my understanding.
By default a regular click on a ListView item is setting the 'checked' state for that item to true. How do I override this behavior so this selection does not happen?
And more fundamentally, what are the underlying ListView mechanics here? Is the row view's default onClick then calling the ListView's onItemClick/LongClick handlers, or how does this click handling get sequenced?
I do want to allow a choiceMode of multipleChoice, but I only want to select it onItemLongClick. Overriding onItemClick does not change this behavior, and overriding the row view's onClick handler in the adapter getView() function seems to prevent the ListView onItemClick and onItemLongClick from ever happening.
Below is more detailed context on my application
My goal is to have my ListActivity display a ListView, which functions as follows:
Clicking an item performs a non-selecting action (expands the row to show more info)
Long clicking an item selects it. Selecting an item is indicated by highlighting the background of the row (as in the Gmail app)
You can select multiple items
My application structure is:
Activity is an extension of ListActivity
Adapter is an extension of ArrayAdapter<>
ListView row layouts are completely custom layouts (not any sort of built-in ListView row layout)
My understanding of the built-in functionality for ListView has me to the point where I am
setting choiceMode to multipleChoice
using the ListView 'checked' functionality for making and tracking the selections
using a custom selector as an 'activatedBackgroundIndicator' to show the highlighting (example here)
Keep an ArrayList to maintain ListView items selected position. When a ListView item is selected check in that ArrayList whether item position is in ArrayList or not. If item is not in ArrayList change state of Item to checked else change state to unchecked and remove the position object from ArrayList. This worked for me.
I have a listview witch supports multiple selections (check boxes).I also have a filter that when i type text in a edit it sorts the listview.
The problem is when I type something and my list gets filtered if I selected a item and then I search another string using the filter it appers checked a diffrent item.
How can I preserve the checked items regardless any filter that I apply to the ListView ?
You need to maintain the state of CheckBox manually due to the recycling behaviour of ListView. I had already written a blog for the same explaining how you can manage that.
ListView with CheckBox Scrolling Issue
All i need is an idea or path to continue searching, i have a list of items that i add to a listview adapter. And i am trying to make some items in the list to have a specific background color (as an example) when the activity loads. Something like having those rows "preselected". The method public ListView getListView() does not help me much.
Thank you either way.
Need to set Multiple Choice Mode via setChoiceMode(), and then you can call setItemChecked() for each of the items you want checked. Then you probably have to make a custom adapter that overrides getView(), cast the parent to ListView and ask if the View (a list item) you are getting at the position given is in fact checked by calling something like getCheckedItems() on the parent. Then you can do what ever you want with that view, like set its background color etc.
In my apps preferences screen, i want to pop up a dialog that shows a list of checkbox items that are dynamically generated.
How does one do that and also, how does one get the checked values? I have made custom dialogs in the past, but for some reason my brain wont function today ...
Thanks.
The way I've done this is to create a ListView that contains rows of CheckBoxes.
private class CheckBoxListAdapter extends ArrayAdapter<CheckBoxListRowItem> {
}
To get the checked values, I call setOnCheckedChangeListener for each CheckBox. Each time it's checked, it updates the my model data (CheckBoxListRowItem). When you need to figure out which CheckBoxes are checked, you can get it from the model data, not directly from the CheckBox object (which is how I thought it should work originally).
I ended up creating an activity that extended ListActivity. Since I wanted a list of checkboxes (where 0 or more could be selected), in my
onCreate():
getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
and I listen for clicks by overriding onListItemClick().
The list adapter that I used was ArrayAdapter:
setListAdapter(
new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_multiple_choice,
some_string_array));