CODEWITHSUNDEEP
androidandroid-listview
Rafael
Rafael

Reputation: 6369

Update existing item in custom ArrayAdapter

I have chat app which have two types of elements in listview

message
message
message
  Header
message
message

In my app after showing Header I need to remove or hide it after particular time or event. I know that I can get this item by position. The problem is that my listview dynamically can grow from both sides. What can I do in this situation. You can see my custom adapter in this question: In Android how to prevent updating existing items on notifyDataSetChanged()

Upvotes: 0

Views: 325

Answers (1)

Emanuel
Emanuel

Reputation: 8106

I would extend a Class by another and give your ArrayAdapter the parent Class.

In your drawer you may work with

 if (position.get(pos) instanceOf MessageHeader) { } 
 else if (position.get(pos) instanceOf SimpleMessage) {}

your Class may look like that:

 class Message {
    private String text;  
 }
 class SimpleMessage extends Message {}
 class HeaderMessage extends Message {}

and your ArrayAdapter accept the Message 

class MyCustomAdapter extends ArrayAdapter<Message> {}

If you want to add or remove items you can use the following way doing that:

 private ArrayList<Message> messages = null;
 public myAdapter(List myList) { this.messages = (ArrayList)myList; }

 public void addItem(Message message) { messages.add(message); forceUpdate(); }
 public void removeItem(int position) {messages.remove(position); forceUpdate(); }
 private voice forceUpdate() { notifyDataSetInvalidated(); notifyDataSetChanged(); }

 private List<Integer> getItemPositionsWithHeader() {
      ArrayList<Integer> list = new ArrayList<>();
      for (int i = 0, j = messages.size(); i <= j; i++) {
          if (messages.get(i) instanceOf HeaderMessage) {
             list.add(i); 
          }
      }
     return list;
 }

private void removeAllHeaderItemsFromList() {
      for (Integer i : getItemPositionsWithHeader) {
          messages.remove(i);
      } 
     forceUpdate();
}

Upvotes: 1

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