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I am new to android developing and I encountered a problem which I can't solve. I implemented an ExpandableListView with a custom Adapter. I have 5 groups and each group has 1 child item. Each group element is of data type: org.myapp.ui.MyClass.

I'm now trying to get the MyClass Object of each group element when expanding it. For that I use the setOnGroupExpandListener:

 lv.setOnGroupExpandListener(new ExpandableListView.OnGroupExpandListener() { 
    public void onGroupExpand (int groupPosition){

      MyClass selected = (MyClass)lv.getAdapter().getItem(groupPosition);
      servId = selected.getServiceId();

      // Do more stuff here
}
});

When I now test this code in the emulator, i get the following ClassCastException, but only after expanding some groups in the ExpandableListView a few times. So for a few times it works and then suddenly it doesn't and i get this exception.

java.lang.ClassCastException: java.lang.String cannot be cast to org.myapp.ui.MyClass

in this code line

MyClass selected = (MyClass)lv.getAdapter().getItem(groupPosition);

If anyone has an idea why this happens (but only after expanding a few groups in the ExpandableListView), please let me know.

share|improve this question
    
You're casting a String object to a 'MyClass' object - these types are incompatiable - getItem will get the text (String) from the adapter position. – Mark Keen Jun 25 '15 at 8:57
    
but it works for about 10 times before it crashes, so i expand the groups of the exlistiew for a couple of times and it works for these times. – Patricia Kopenhagen Jun 25 '15 at 9:04
    
do you know another way of getting the object of each group item when expanding it? – Patricia Kopenhagen Jun 25 '15 at 9:26
    
solved it myself with this: MyClass selected = (MyClass) lv.getExpandableListAdapter().getGroup(groupPosition); – Patricia Kopenhagen Jun 25 '15 at 10:07
    
Glad to hear .. Always the most satisfying way to solve a problem :) – Mark Keen Jun 25 '15 at 11:10
up vote 1 down vote

Taken from oracle docs, ClassCastException Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance. For example, the following code generates a ClassCastException:

 Object x = new Integer(0);
 System.out.println((String)x);

In your case you are trying to convert a string to a custom class which will never pass because the line lv.getAdapter().getItem(groupPosition) gives String instead of MyClass Object.

share|improve this answer
    
But why does it work for a couple of times and then all of a sudden it crashes? That is what is confusing me. – Patricia Kopenhagen Jun 25 '15 at 9:06
    
It never works..as long as your method returning String – Bhargav Kumar R Jun 25 '15 at 9:09
    
do you know if there is another way to get the object of each group item when expanding it? so what i want is to get the object of the group item which i am expanding. – Patricia Kopenhagen Jun 25 '15 at 9:11
    
Refer the class API once.. – Bhargav Kumar R Jun 25 '15 at 9:13

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