Also versuche ich das zu benutzenPicasso-Bibliothek zum Herunterladen und Zwischenspeichern von Bildern. Um die contactUri zu übergebenPicasso Ich muss eine Anfrage an die Kontakte stellenContent Provider. Da ich den Haupt-UI-Thread nicht blockieren möchte, um die Kontakt-ID zu erhalten, habe ich dies in eine eingefügtAsyncTask. Und sobald ich diese Kontakt-ID erhalte, rufe ich anPicasso in demonPostExecute() Methode derAsyncTask.

Ich bemerke jedoch ein Flackern, das auftaucht, wenn ich durch meinen Bildschirm scrolleListView schnell. Es scheint mir, dass es ein Problem mit dem gibtViewHolder da in den wiederverwendeten Ansichten das vorherige Bild angezeigt wird, bevor das entsprechende Bild eingestellt wird. Gibt es sowieso, um dies zu vermeiden?

public class ConversationThreadsCursorAdapter extends SimpleCursorAdapter {

    // region Constants
    private static final int RECIPIENT_IDS_COLUMN_INDEX = 3;
    private static final int ID2_COLUMN_INDEX = 0;
    private static final int ADDRESS_COLUMN_INDEX = 1;
    // endregion

    // region Variables
    private final String DEBUG_TAG = getClass().getSimpleName().toString();

    private Context mContext;
    protected Drawable mDefaultPicDrawable;
    protected ContentResolver mContentResolver;
    protected LinearLayout.LayoutParams mContactPicLayoutParams;
    // endregion

    // region Constructors
    public ConversationThreadsCursorAdapter(Context context, int layout,
    Cursor c, String[] from, int[] to, int flags) {
        super(context, layout, c, from, to, flags);
        mContext = context;
        mDefaultPicDrawable = mContext.getResources().getDrawable(
        R.drawable.ic_contact_picture);
        mContactPicLayoutParams = new LinearLayout.LayoutParams(
        mDefaultPicDrawable.getIntrinsicWidth(),
        mDefaultPicDrawable.getIntrinsicHeight());

    }
    // endregion

    public View getView(final int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = null;

        if (convertView == null) {
            convertView = mLayoutInflater.inflate(R.layout.simple_message, null);

            // Creates a ViewHolder and store references to the children
            // views we want to bind data to.
            viewHolder = setupViewHolder(convertView);

            convertView.setTag(viewHolder);

        } else {
            // Get the ViewHolder back to get fast access to the TextView
            // and the ImageView.
            viewHolder = (ViewHolder) convertView.getTag();
            viewHolder.task.cancel(true);


        }

        mCursor = getCursor();

        mCursor.moveToPosition(position);

        viewHolder.position = position;

        String recipient_ids = mCursor.getString(RECIPIENT_IDS_COLUMN_INDEX);

        String[] recipients = recipient_ids.split(" ");

        viewHolder.task = new AddressFetcherTask(viewHolder, position);
        viewHolder.task.execute(recipients); 

        return convertView;

    }

    // region Helper Methods
    private ViewHolder bindUIElements(View convertView) {
        ViewHolder viewHolder = new ViewHolder();

        viewHolder.contactBadge = (QuickContactBadge) convertView.findViewById(R.id.contact_pic);
        return viewHolder;
    }

    private ViewHolder setupViewHolder(View convertView) {
        ViewHolder viewHolder = bindUIElements(convertView);

        viewHolder.contactBadge.setLayoutParams(mContactPicLayoutParams);
        return viewHolder;
    }
    // endregion

    // region Inner Classes

    private class ViewHolder {
        QuickContactBadge contactBadge;
        int position;
    }

    private class AddressFetcherTask extends AsyncTask < String[], Void, Integer > {
        private ViewHolder mViewHolder;
        private int mPosition;

        public AddressFetcherTask(ViewHolder viewHolder, int position) {
            mViewHolder = viewHolder;
            mPosition = position;
        }

        @Override
        protected Integer doInBackground(String[]...recipients) {
            String recipient = recipients[0][0];
            Log.d(DEBUG_TAG, "recipient is " + recipient);
            Cursor c = mContentResolver.query(
            Uri.parse("content://mms-sms/canonical-addresses"), null, "_id = " + recipient, null, null);

            String _id = "";
            String address = "";
            while (c.moveToNext()) {
                _id = c.getString(ID2_COLUMN_INDEX);
                address = c.getString(ADDRESS_COLUMN_INDEX);
            }
            c.close();

            int contactId;
            if (address != null) {
                contactId = ContactsUtils.getContactId(mContext, address, "address");
            } else {
                contactId = Integer.valueOf(address);
            }
            return contactId;
        }

        @Override
        protected void onPostExecute(Integer contactId) {

            if (mViewHolder.position == mPosition) {
                Picasso.with(mContext)
                    .load(getContactUri(contactId))
                    .placeholder(R.drawable.ic_contact_picture)
                    .into(mViewHolder.contactBadge);

            }
        }
    }
    // endregion

}