Question

I have a ListView listing a custom object (let’s say MyObject).

I want to filter it dynamically through an EditText so I had to implement a getFilter() with a publishResults method:

@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
    MyObjectAdapter.this.setItems((List<MyObject>) results.values);
    MyObjectAdapter.this.notifyDataSetChanged();
}

At this point, Eclipse complains: Type safety: Unchecked cast from Object to List<MyObject>

I am sure this cast will always be true, but Eclipse only suggests to add @SuppressWarnings("unchecked") but I’m totally against SuppressWarnings because it’s only hiding the problem, not a solution…

I tried adding:

if(results.values instanceof List<MyObject>)

But Eclipse complains again, and this solves nothing…

Cannot perform instanceof check against parameterized type List<MyObject>. Use the form List<?>

I know the casting will always be correct, but which is the proper way to make the code to be sure results.values is actually a List<MyObject> ?

Thanks in advance!

Answer 1

Well, I finally managed to find a solution.

Just as @Medo42 said:

Another option is to check for and cast to List as the instanceof
error suggests. Then you can iterate over the elements in the list and
check if they are actually all instances of MyObject, and copy them to
a new List.

Even though I did not went through the process of creating a whole new object in order to make this particular case to work “warning-less” this was the right direction to go.

So I took @lokoko ‘s idea and use it in a new setItems() method, with an Object parameter instead of a List<MyObject> in order to make sure

The result code is the following:

public void setItems(List<MyObject> var){
    this.list = var;
}

public void setItems(Object var){
    List<MyObject> result = new ArrayList<MyObject>();
    if (var instanceof List){
        for(int i = 0; i < ((List<?>)var).size(); i++){
            Object item = ((List<?>) var).get(i);
            if(item instanceof MyObject){
                result.add((MyObject) item);
            }
        }
    }
    setItems(result);
}

Thanks everyone for your help!