CODEWITHSUNDEEP
androidlistview
Andrey Gein
Andrey Gein

Reputation: 81

Adding new elements to the top of the ListView

I'm writing an IM client and I need to download (from filesystem or network) and show new elements at the top of ListView (it is history of messages -- older messages are at the top, newer -- at the bottom). I implemented my own Adapter for ListView but I can't add new elements at the beginning of the list and redraw it. (notifyDataSetChanged() isn't good for me, because indexes of messages in ListView changes and android can't redraw it normally).

How do other apps do something similar?

I don't create special code for it, I am simply creating new Adapter for my ListView:

messagesListView.setAdapter(new MessagesListAdapter(this));

And redefine getView() and getCount() method in MessagesListAdapter (extends ArrayAdapter now).

My XML for ListView is

<ListView
  android:id="@+id/dialog_messages_list"
  android:layout_height="fill_parent"
  android:layout_width="fill_parent"
  android:layout_marginTop="@dimen/title_height">
</ListView>

And my XML for one element (one message) is 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal" >

  <TextView
      android:id="@+id/dialogMessageText"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text=""
      android:background="@drawable/dialog_message_in"
      />

  <TextView
    android:id="@+id/dialogMessageDatetime"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text=""/>

</LinearLayout>

May be you need other code?

EDIT: I tried 

    messagesListView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList));
    (new Thread() {
        public void run() {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            arrayList.add(0, "qwer");
        }
    }).start();

But it also not seems good. I tried to call ((ArrayAdapter<String>)messagesListView.getAdapter()).notifyDataSetChanged(); in thread, but it makes exception.

Upvotes: 3

Views: 1789

Answers (2)

Sam
Sam

Reputation: 86948

I suggest reversing the order of the List to display the newest result first.

Run this example:

public class Example extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        String[] array = {"oldest", "older", "old", "new", "newer"};
        List<String> list = new ArrayList<String>();
        Collections.addAll(list, array);
        Collections.reverse(list);

        // When you want to add new Strings, put them at the beginning of list
        list.add(0, "newest");

        ListView listView = (ListView) findViewById(R.id.list);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, list);
        listView.setAdapter(adapter);
    }
}

You don't have to override anything in the ArrayAdapter or ListView this way.

Upvotes: 2

user1276567
user1276567

Reputation:

you can programmatically add some views in the class associated with your list view. For example:

To add stuff to a layout and make new elements:

TextView tv = new TextView(getApplicationContext());
EditText edit = new EditText(getApplicationContext());
relative.addView(tv);
relative.addView(edit);

This is to manipulate an existing element in the xml layout:

final TextView tv = (TextView) v.findViewById(R.id.listItem);
    tv.setText("This an item I am changing");

If you look at some of the related questions, they will give your more information on this. But you can also checkout other people's custom listviews and adapters online. This one is really nice: http://www.androidhive.info/2012/02/android-custom-listview-with-image-and-text/

Upvotes: 0

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