Ollie C Ollie C - 6 months ago 60
Android Question

Why is ListView.getCheckedItemPositions() not returning correct values?

The app has a ListView with multiple-selection enabled, in the UI it works as expected. But when I read the values out using this code:

Log.i(TAG,"Entered SearchActivity.saveCategoryChoice()");
SparseBooleanArray checkedPositions = categorySelector.getCheckedItemPositions();
Log.i(TAG,"checkedPositions: " + checkedPositions.size());
if (checkedPositions != null)
{
int count = categoriesAdapter.getCount();
for ( int i=0;i<count;i++)
{
Log.i(TAG,"Selected items: " + checkedPositions.get(i));
}
}


I get this output, no matter what state each checkbox is in:

Entered SearchActivity.saveCategoryChoice()
checkedPositions: 0
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false
Selected items: false


The SparseBooleanArray seems to return false for any non-existent item, so the source of the problems seems to be that getCheckedItemPositions() is returning an empty array. The method is behaving as if there are no items in the ListView, but there are.

I can see from the docs that no values are returned when the ListView is not set up as multi-select, but it is, using this statement:

categorySelector.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);


In my scenario, the adapter I'm using is a subclass of ArrayAdapter, and (without any solid evidence) I suspect this may be the cause, though I can't see why it shouldn't work.

Answer

I still do not know why, but in my scenario, getCheckedItemPositions() returns false values for all items. I cannot see a way to use the methods on the ListView to get the boolean values out. The SparseBooleanArray object seems to have no real-world data in it. I suspect this may be because of some quirk of my implementation, perhaps that I've subclassed ArrayAdapter. It's frustrating, issues like this are a real time-drain.

Anyway, the solution I have used is to to attach a handler to each Checkbox individually as ListView rows are created. So from ListView.getView() I call this method:

private void addClickHandlerToCheckBox(CheckBox checkbox)
{
    checkbox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
    public void onCheckedChanged(CompoundButton arg0, boolean arg1) {
        CheckBox checkbox = (CheckBox)arg0; 
        boolean isChecked = checkbox.isChecked();
        // Store the boolean value somewhere durable
    }
      }
);