Lazy Charger les images sur Listview dans android (niveau débutant)? [dupliquer]

Question

  

Possible en double:    Android - Comment puis-je faire un paresseux chargement d'images dans ListView

Je travaille sur le listview avec l'adaptateur personnalisé. Je veux charger les images et affichage de texte sur elle. Les images sont la charge des urls Internet. Je veux juste montrer les images qui sont un élément de liste visible à l'utilisateur de hte. Je refered commonsware efficace et lent Adaptateur en ApiDemos est plus utile de comprendre.

Les changements effectués sur exemple d'adaptation efficace comme ceci:

public class List14 extends ListActivity implements ListView.OnScrollListener {
// private TextView mStatus;

private static boolean mBusy = false;
static ViewHolder holder;

public static class EfficientAdapter extends BaseAdapter {
    private LayoutInflater mInflater;
    private Bitmap mIcon1;
    private Bitmap mIcon2;

    public EfficientAdapter(Context context) {
        // Cache the LayoutInflate to avoid asking for a new one each time.
        mInflater = LayoutInflater.from(context);

        // Icons bound to the rows.
        mIcon1 = BitmapFactory.decodeResource(context.getResources(),
                R.drawable.icon48x48_1);
        mIcon2 = BitmapFactory.decodeResource(context.getResources(),
                R.drawable.icon48x48_2);
    }

    /**
     * The number of items in the list is determined by the number of
     * speeches in our array.
     * 
     * @see android.widget.ListAdapter#getCount()
     */
    public int getCount() {
        return DATA.length;
    }

    /**
     * Since the data comes from an array, just returning the index is
     * sufficent to get at the data. If we were using a more complex data
     * structure, we would return whatever object represents one row in the
     * list.
     * 
     * @see android.widget.ListAdapter#getItem(int)
     */
    public Object getItem(int position) {
        return position;
    }

    /**
     * Use the array index as a unique id.
     * 
     * @see android.widget.ListAdapter#getItemId(int)
     */
    public long getItemId(int position) {
        return position;
    }

    /**
     * Make a view to hold each row.
     * 
     * @see android.widget.ListAdapter#getView(int, android.view.View,
     *      android.view.ViewGroup)
     */
    public View getView(int position, View convertView, ViewGroup parent) {
        // A ViewHolder keeps references to children views to avoid
        // unneccessary calls
        // to findViewById() on each row.

        // When convertView is not null, we can reuse it directly, there is
        // no need
        // to reinflate it. We only inflate a new View when the convertView
        // supplied
        // by ListView is null.
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.list_item_icon_text,
                    null);

            // Creates a ViewHolder and store references to the two children
            // views
            // we want to bind data to.
            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.text);
            holder.icon = (ImageView) convertView.findViewById(R.id.icon);

            convertView.setTag(holder);
        } else {
            // Get the ViewHolder back to get fast access to the TextView
            // and the ImageView.
            holder = (ViewHolder) convertView.getTag();
        }
        if (!mBusy) {
            holder.icon.setImageBitmap(mIcon1);

            // Null tag means the view has the correct data
            holder.icon.setTag(null);
        } else {
            holder.icon.setImageBitmap(mIcon2);

            // Non-null tag means the view still needs to load it's data
            holder.icon.setTag(this);
        }
        holder.text.setText(DATA[position]);

        // Bind the data efficiently with the holder.
        // holder.text.setText(DATA[position]);

        return convertView;
    }

    static class ViewHolder {
        TextView text;
        ImageView icon;
    }
}

private Bitmap mIcon1;
private Bitmap mIcon2;
@Override
public void onCreate(Bundle savedInstanceState) {
    mIcon1 = BitmapFactory.decodeResource(this.getResources(),
            R.drawable.icon48x48_1);
    mIcon2 = BitmapFactory.decodeResource(this.getResources(),
            R.drawable.icon48x48_2);
    super.onCreate(savedInstanceState);
    setListAdapter(new EfficientAdapter(this));
    getListView().setOnScrollListener(this);
}

public void onScroll(AbsListView view, int firstVisibleItem,
        int visibleItemCount, int totalItemCount) {
}

public void onScrollStateChanged(AbsListView view, int scrollState) {
    switch (scrollState) {
    case OnScrollListener.SCROLL_STATE_IDLE:
        mBusy = false;

        int first = view.getFirstVisiblePosition();
        int count = view.getChildCount();
        for (int i = 0; i < count; i++) {

            holder.icon = (ImageView) view.getChildAt(i).findViewById(
                    R.id.icon);
            if (holder.icon.getTag() != null) {
                holder.icon.setImageBitmap(mIcon1);
                holder.icon.setTag(null);
            } 
        }

        // mStatus.setText("Idle");
        break;
    case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
        mBusy = true;
        // mStatus.setText("Touch scroll");
        break;
    case OnScrollListener.SCROLL_STATE_FLING:
        mBusy = true;
        // mStatus.setText("Fling");
        break;
    }
}
private static final String[] DATA = { "Abbaye de Belloc",
        "Abbaye du Mont des Cats", "Abertam", "Abondance", "Ackawi",
        "Acorn", "Adelost", "Affidelice au Chablis", "Afuega'l Pitu"};
}

Il fonctionne très bien maintenant. Mais lorsque l'état de défilement sa non rechargeant l'image correctement. un intervalle d'articles ne montre pas la images2. qui est l'ordre des images sont en cours de chargement. Mais pas dans tous les articles de la liste. Discordances qui se passent entre les intervalles de point solides. comment corriger?

Answer 1

Praveen -

Comme vous l'avez déjà trouvé mon billet de blog sur ce sujet, je voulais juste repousser à Stackoverflow afin que d'autres puissent l'utiliser.

Voici la discussion de base: http: // ballardhack. wordpress.com/2010/04/05/loading-remote-images-in-a-listview-on-android/

Et il y a une classe plus tard que je documenté utilise un fil et un rappel pour charger les images:

http://ballardhack.wordpress.com/2010/04/10/loading-images-over-http-on-a-separate-thread-on-android/

Mise à jour: Pour répondre à votre exception spécifique, je pense que vue retourné dans la liste de getChildAt n'est pas une ImageView - il y a tout ce que la mise en page vue que vous utilisez pour maintenir l'image et le texte.

Mise à jour pour inclure le code correspondant : (Par @ recommandation george-stockeur)

Voici l'adaptateur que j'utilisais:

public class MediaItemAdapter extends ArrayAdapter<MediaItem> {
  private final static String TAG = "MediaItemAdapter";
  private int resourceId = 0;
  private LayoutInflater inflater;
  private Context context;

  private ImageThreadLoader imageLoader = new ImageThreadLoader();

  public MediaItemAdapter(Context context, int resourceId, List<MediaItem> mediaItems) {
    super(context, 0, mediaItems);
    this.resourceId = resourceId;
    inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.context = context;
  }

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {

    View view;
    TextView textTitle;
    TextView textTimer;
    final ImageView image;

    view = inflater.inflate(resourceId, parent, false);

    try {
      textTitle = (TextView)view.findViewById(R.id.text);
      image = (ImageView)view.findViewById(R.id.icon);
    } catch( ClassCastException e ) {
      Log.e(TAG, "Your layout must provide an image and a text view with ID's icon and text.", e);
      throw e;
    }

    MediaItem item = getItem(position);
    Bitmap cachedImage = null;
    try {
      cachedImage = imageLoader.loadImage(item.thumbnail, new ImageLoadedListener() {
      public void imageLoaded(Bitmap imageBitmap) {
      image.setImageBitmap(imageBitmap);
      notifyDataSetChanged();                }
      });
    } catch (MalformedURLException e) {
      Log.e(TAG, "Bad remote image URL: " + item.thumbnail, e);
    }

    textTitle.setText(item.name);

    if( cachedImage != null ) {
      image.setImageBitmap(cachedImage);
    }

    return view;
  }
}

Answer 2

Je l'ai. Ce code est parfait que je veux. chargement Lazy fonctionne à l'adaptateur personnalisé seulement des icônes de poste de liste visible. Hope it helps aux débutants

public class List14 extends ListActivity implements ListView.OnScrollListener {
// private TextView mStatus;

private static boolean mBusy = false;
static ViewHolder holder;

public static class EfficientAdapter extends BaseAdapter {
    private LayoutInflater mInflater;
    private Bitmap mIcon1;
    private Bitmap mIcon2;
    private Context mContext;

    public EfficientAdapter(Context context) {
        // Cache the LayoutInflate to avoid asking for a new one each time.
        mInflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        mContext = context;
        // Icons bound to the rows.
        mIcon1 = BitmapFactory.decodeResource(context.getResources(),
                R.drawable.icon48x48_1);
        mIcon2 = BitmapFactory.decodeResource(context.getResources(),
                R.drawable.icon48x48_2);
    }

    /**
     * The number of items in the list is determined by the number of
     * speeches in our array.
     * 
     * @see android.widget.ListAdapter#getCount()
     */
    public int getCount() {
        return DATA.length;
    }

    /**
     * Since the data comes from an array, just returning the index is
     * sufficent to get at the data. If we were using a more complex data
     * structure, we would return whatever object represents one row in the
     * list.
     * 
     * @see android.widget.ListAdapter#getItem(int)
     */
    public Object getItem(int position) {
        return position;
    }

    /**
     * Use the array index as a unique id.
     * 
     * @see android.widget.ListAdapter#getItemId(int)
     */
    public long getItemId(int position) {
        return position;
    }

    /**
     * Make a view to hold each row.
     * 
     * @see android.widget.ListAdapter#getView(int, android.view.View,
     *      android.view.ViewGroup)
     */
    public View getView(int position, View convertView, ViewGroup parent) {
        // A ViewHolder keeps references to children views to avoid
        // unneccessary calls
        // to findViewById() on each row.

        // When convertView is not null, we can reuse it directly, there is
        // no need
        // to reinflate it. We only inflate a new View when the convertView
        // supplied
        // by ListView is null.
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.list_item_icon_text,
                    parent, false);

            // Creates a ViewHolder and store references to the two children
            // views
            // we want to bind data to.
            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.text);
            holder.icon = (ImageView) convertView.findViewById(R.id.icon);

             convertView.setTag(holder);
        } else {
            // Get the ViewHolder back to get fast access to the TextView
            // and the ImageView.
             holder = (ViewHolder) convertView.getTag();
        }

        if (!mBusy) {

            holder.icon.setImageBitmap(mIcon1);

            // Null tag means the view has the correct data
            holder.icon.setTag(null);

        } else {
            holder.icon.setImageBitmap(mIcon2);

            // Non-null tag means the view still needs to load it's data
            holder.icon.setTag(this);
        }
        holder.text.setText(DATA[position]);

        // Bind the data efficiently with the holder.
        // holder.text.setText(DATA[position]);

        return convertView;
    }

    static class ViewHolder {
        TextView text;
        ImageView icon;
    }
}

private Bitmap mIcon1;
private Bitmap mIcon2;

@Override
public void onCreate(Bundle savedInstanceState) {
    mIcon1 = BitmapFactory.decodeResource(this.getResources(),
            R.drawable.icon48x48_1);
    mIcon2 = BitmapFactory.decodeResource(this.getResources(),
            R.drawable.icon48x48_2);
    super.onCreate(savedInstanceState);
    setListAdapter(new EfficientAdapter(this));
    getListView().setOnScrollListener(this);
}

public void onScroll(AbsListView view, int firstVisibleItem,
        int visibleItemCount, int totalItemCount) {
}

public void onScrollStateChanged(AbsListView view, int scrollState) {
    switch (scrollState) {
    case OnScrollListener.SCROLL_STATE_IDLE:
        mBusy = false;

        int first = view.getFirstVisiblePosition();
        int count = view.getChildCount();

        for (int i = 0; i < count; i++) {

            holder.icon = (ImageView) view.getChildAt(i).findViewById(
                    R.id.icon);
            if (holder.icon.getTag() != null) {
                holder.icon.setImageBitmap(IMAGE[first+i]);// this is the image url array.
                holder.icon.setTag(null);
            }
        }

        // mStatus.setText("Idle");
        break;
    case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
        mBusy = true;
        // mStatus.setText("Touch scroll");
        break;
    case OnScrollListener.SCROLL_STATE_FLING:
        mBusy = true;
        // mStatus.setText("Fling");
        break;
    }
}

private static final String[] DATA = { "Abbaye de Belloc",
        "Abbaye du Mont des Cats", "Abertam", "Abondance", "Ackawi",
        "Acorn", "Adelost", "Affidelice au Chablis", "Afuega'l Pitu",
        "Yarra Valley Pyramid", "Yorkshire Blue", "Zamorano",
        "Zanetti Grana Padano", "Zanetti Parmigiano Reggiano" };
  }

Answer 3

Pour autant que je comprends que vous devez mettre à jour votre liste après le défilement est terminée. C'est facile. Voici le code fixe pour vous:

EfficientAdapter adapter;

@Override
public void onCreate(Bundle savedInstanceState) {
    mIcon1 = BitmapFactory.decodeResource(this.getResources(),
            R.drawable.icon48x48_1);
    mIcon2 = BitmapFactory.decodeResource(this.getResources(),
            R.drawable.icon48x48_2);
    super.onCreate(savedInstanceState);
    adapter=new EfficientAdapter(this);
    setListAdapter(adapter);
    getListView().setOnScrollListener(this);
}

public void onScroll(AbsListView view, int firstVisibleItem,
    int visibleItemCount, int totalItemCount) {
}

public void onScrollStateChanged(AbsListView view, int scrollState) {
    switch (scrollState) {
    case OnScrollListener.SCROLL_STATE_IDLE:
        mBusy = false;
        adapter.notifyDataSetChanged() 
        break;
    case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
        mBusy = true;
        // mStatus.setText("Touch scroll");
        break;
    case OnScrollListener.SCROLL_STATE_FLING:
        mBusy = true;
        // mStatus.setText("Fling");
        break;
    }
}

notifyDataSetChanged racontera l'adaptateur pour réafficher tous les éléments visibles, donc ils seront affichés avec image2.

Answer 4

Pour autant que je peux voir, la ViewHolder de statique n'aide rien. Essayez de mettre l'ensemble de la fonction onScrollStateChanged entre /* et */, supprimant la ligne de static ViewHolder et changer holder = new ViewHolder(); à ViewHolder holder = new ViewHolder();.

Answer 5

Ah, vérifiez votre logcat pour vous assurer que votre application n'est pas tué et redémarré. La plupart des combinés limitent la taille de votre application totale de 16 Mo ou 24 Mo. Il est facile de charger un groupe d'images, courir sur, se faire tuer, redémarrer, et que votre OnPause charge pas gros volumes de données hors de l'écran. Il est la collection de garabage pauvre homme.