Every time you click your button you're re-initializing your ArrayList.

Code:
array1 = new ArrayList<String>();
array1.add(plek);
array2 = new ArrayList<String>();
array2.add(naam);
Move the array1/2 = new ArrayList<String>(); to where you're declaring the list instead.

change
Code:
ArrayList<String> array1;
ArrayList<String> array2;
to

Code:
ArrayList<String> array1 = new ArrayList<String>();
ArrayList<String> array2 = new ArrayList<String>();
and then change the first bit of code to

Code:
array1.add(plek);
array2.add(naam);