添加新项目时，ListView在屏幕上未更新

Question

I am designing a film application for displaying different films,

I make a call to an AsyncTask thread and receive the returning call :

@Override
public void processFinish(final ArrayList<Film> output) {
    generateFilmList(output);
}

Using the film data i generate the list view :

public void generateFilmList(final ArrayList<Film> films) {
    ListView lv = (ListView) findViewById(R.id.listView);
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> a, View v, int position,
                                long id) {
            Intent intent = new Intent(Film_List.this, Film_Details.class);
            Bundle b = new Bundle();
            b.putParcelable("film", films.get(position));
            intent.putExtras(b);
            startActivity(intent);
        }
    });
    if (la == null) {
        la = new ListAdapter(this, films);
        lv.setAdapter(la);
    } else {
        runOnUiThread(new Thread(new Runnable() {
            public void run() {
                la.clear();
                la.addAll(films);
            }
        }));

    }
    la.notifyDataSetChanged();
    lv.setSelectionAfterHeaderView();

}

This is my list adapter :

public class ListAdapter extends ArrayAdapter<Film> {

    private final Context context;
    private ArrayList<Film> films;
    private View rowView;

    public ListAdapter(Context context, ArrayList<Film> films) {
        super(context, R.layout.row, films);
        this.context = context;
        this.films = films;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        rowView = inflater.inflate(R.layout.row, parent, false);
        generateTitle(position);
        generateTag(position);
        generateImage(position);
        return rowView;
    }

    public void generateTitle(final int position) {
        TextView title = (TextView) rowView.findViewById(R.id.text_title);
        title.setText(films.get(position).getTitle());
    }

    public void generateTag(final int position) {
        TextView tag = (TextView) rowView.findViewById(R.id.text_description);
        tag.setText(films.get(position).getTag());
    }

    public void generateImage(final int position) {
        final ImageView image = (ImageView) rowView.findViewById(R.id.image_poster);
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    URL url = new URL(films.get(position).getImg());
                    Bitmap bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
                    image.setImageBitmap(bmp);
                } catch (Exception e) {
                    new Debugger().print(e.toString());
                }
            }
        });
        thread.start();
    }

}

I display only 20 films in a list view for each page, so when calling a new page i generate a new query with the new page value:

public void nextPage(View view) {
    this.page = page + 1;
    new Debugger().print(Integer.toString(page));
    generateFilmQuery();
}

This also updates my listview with the new values.

My problem is that although the list view is updated because the list adapter has been altered. The screen is not displaying the changes until I SCROLL down on the page. This doesn't make sense as I am calling notifyDataSetChanged , although this doesn't do anything!

Answer 1

I hope it will helpful for you.

Add a method in ListAdapter

pubilc void addItems(ArrayList<Film> films)
{
   this.films = films;
}

And change your code like this

 runOnUiThread(new Thread(new Runnable() {
                public void run() {
                    la.addItems(new ArrayList<Film>());
                    la.notifyDataSetChanged();
                    la.addItems(films);
                    la.notifyDataSetChanged();
                }
            }));