I want to implement predefined filters for a ListView. My ListView will contain numbers and there would be a Filter icon which on click should show options like "Show odd", "Show even" and "Show all".
How to display a popup dialog on click of the Filter icon? If that is achieved using a simple popup dialog, then how do I filter the ListView with the option selected? I tried searching Android forums but they speak mainly about text filters.
You could implement a Filter like so:
class MyFilter extends Filter {
private final MyAdapter myAdapter;
public MyFilter(MyAdapter myAdapter) {
this.myAdapter = myAdapter;
}
@Override
protected Filter.FilterResults performFiltering(CharSequence constraint) {
FilterResults results = new FilterResults();
if (constraint == null || constraint.length() == 0) {
// unfiltered: show all
results.values = myAdapter.getOriginalList();
results.count = myAdapter.getOriginalList().size();
} else {
// filtered
List<Integer> newWorkingList = new ArrayList<>();
if (constraint.equals('1')) {
// odd
for (Integer integer : myAdapter.getOriginalList()) {
if (integer % 2 == 1) {
newWorkingList.add(integer);
}
}
} else if (constraint.equals('2')) {
// even
for (Integer integer : myAdapter.getOriginalList()) {
if (integer % 2 == 0) {
newWorkingList.add(integer);
}
}
}
results.values = newWorkingList;
results.count = newWorkingList.size();
}
return results;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
myAdapter.setFilteredList((List<String>) results.values);
if (results.count == 0) {
myAdapter.notifyDataSetInvalidated();
} else {
myAdapter.notifyDataSetChanged();
}
}
}
In your adapter class you have to make changes similar to these:
public class MyAdapter extends ArrayAdapter<Integer> implements Filterable
private MyFilter MyFilter;
@Override
public Filter getFilter() {
if (myFilter == null) {
myFilter = new myFilter(this);
}
return myFilter;
}
And you have to add a setter for your original list.
And, finally, in the listener of your popup dialog you have to add these lines depending on the user's choice:
myAdapter.getFilter().filter(null);
myAdapter.getFilter().filter('1');
myAdapter.getFilter().filter('2');
