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android – Unable to modify ArrayAdapter in ListView: UnsupportedOperationException

Posted by: admin March 11, 2020 Leave a comment

Questions:

I’m trying to make a list containing names. This list should be modifiable (add, delete, sort, etc). However, whenever I tried to change the items in the ArrayAdapter, the program crashed, with java.lang.UnsupportedOperationException error. Here is my code:

ListView panel = (ListView) findViewById(R.id.panel);
String[] array = {"a","b","c","d","e","f","g"};
final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, array);
adapter.setNotifyOnChange(true);
panel.setAdapter(adapter);

Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
      adapter.insert("h", 7);
   }
});

I tried insert, remove and clear methods, and none of them worked. Would someone tell me what I did wrong?

How to&Answers:

I tried it out, myself…Found it didn’t work. So i check out the source code of ArrayAdapter and found out the problem. The ArrayAdapter, on being initialized by an array, converts the array into a AbstractList (List) which cannot be modified.

Solution
Use an ArrayList<String> instead using an array while initializing the ArrayAdapter.

String[] array = {"a","b","c","d","e","f","g"}; 
ArrayList<String> lst = new ArrayList<String>(Arrays.asList(array));
final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, 
android.R.layout.simple_list_item_1, lst); 

Cheers!