Question

I have a ListView that is filled with items of an ArrayAdapter.
Now I want to strike them out when click and also check in the beginning if they are already struck through(calling an external api etc).
But it only works in the onItemClickListener the method above it doesn’t.
to understand it better, here is some code:

public void machListe() { 
   listViewArrayAdapter = new ArrayAdapter(getApplicationContext(),R.layout.task_item, ti);
   taskListe.setAdapter(listViewArrayAdapter);
   TextView ab=(TextView) taskListe.getChildAt(0);

So if I Debugg now I see that ab is null.

taskListe.setOnItemClickListener(new OnItemClickListener() { 

   public void onItemClick(AdapterView<?> arg0, View arg1,int arg2, long arg3) {

     TextView ab=(TextView) taskListe.getChildAt(0);

If I debug here, ab is NOT null.

Answer 1

You are trying to saft the state of the tasks inside your Views.

You should try to separate Model and View at this point.
Create a Model Object that contains a single task then extend ArrayAdapter and overwrite getView. In the getView you retrieve the correct task from the task list. Create the textview for the task and if the task is marked as done in your model you cancel out the text.

If you try to change the views in a list after they are created you would have to do this every time the list stops scrolling because the list will only hold childviews for the items that are shown on the screen, the other views are created during scrolling to save memory.

The only correct place to change a listview Item is in the getView method of the corresponding Adapter.

Have a look at the ListsView Tutorial on vogella.de for more information.