我的列表视图未显示图像在其各自自定义适配器上的确切位置。我正在尝试使用AsyncTask加载图像。有时图像重复，我不知道为什么。这是我的ArrayAdapter代码：
public class NewsPromoAdapter extends ArrayAdapter<NewsPromosDTO> {
private final Context context;
List<NewsPromosDTO> npList;
LayoutInflater inflater;
Bitmap src;
public NewsPromoAdapter(Context context, List<NewsPromosDTO> npList) {
super(context, R.layout.news_and_promos, npList);
this.context = context;
this.npList = npList;
inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public static class ViewHolder {
TextView nameText;
TextView date1Text;
ImageView imageView;
ProgressBar prg;
LoadImage loadImg;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = inflater.inflate(R.layout.news_and_promos, parent,
false);
holder = new ViewHolder();
holder.nameText = (TextView) convertView
.findViewById(R.id.newspromo_name);
holder.date1Text = (TextView) convertView
.findViewById(R.id.newspromo_date);
holder.imageView = (ImageView) convertView
.findViewById(R.id.newspromo_imageView);
holder.prg = (ProgressBar) convertView
.findViewById(R.id.progressBar1);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
holder.loadImg.cancel(true);
}
if (!(npList.get(position).getName().equals(""))) {
holder.nameText.setVisibility(View.VISIBLE);
holder.nameText.setText(npList.get(position).getName());
} else {
holder.nameText.setVisibility(View.GONE);
}
if (!(npList.get(position).getDate().equals(""))) {
holder.date1Text.setVisibility(View.VISIBLE);
holder.date1Text.setText(npList.get(position).getDate());
} else {
holder.date1Text.setVisibility(View.GONE);
}
if (!(npList.get(position).getImageURL().equals(""))) {
holder.imageView.setVisibility(View.VISIBLE);
holder.loadImg = new LoadImage(holder.imageView, npList.get(
position).getImageURL(), holder);
holder.loadImg.execute();
} else {
holder.imageView.setVisibility(View.GONE);
holder.prg.setVisibility(View.GONE);
}
return convertView;
}
class LoadImage extends AsyncTask<Object, Void, Bitmap> {
ViewHolder viewH;
private ImageView imv;
private String url;
public LoadImage(ImageView imv, String imageURL, ViewHolder viewH) {
this.imv = imv;
this.url = imageURL;
this.viewH = viewH;
}
@Override
protected Bitmap doInBackground(Object... params) {
BitmapFromURL bmpURL = new BitmapFromURL();
src = bmpURL.getBitmapFromURL(url);
return src;
}
@Override
protected void onPostExecute(Bitmap result) {
// imv.setImageBitmap(result);
// viewH.prg.setVisibility(View.GONE);
viewH.prg.setVisibility(View.GONE);
imv.setImageBitmap(result);
}
}
}
这是处理ADAPTER的Activity。我正在实现一些大型网站使用的Endless listview方法。像Facebook，Twitter等。滚动到底部时，新项目加载到列表视图中。我不确定我是否做得很好。
public class ListNewsPromoActivity extends Activity {
List<NewsPromosDTO> npList;
String url, user_email;
Bundle extras;
int user_points;
List<Integer> npIDs;
private ProgressDialog progressDialog;
BitmapFromURL bmpURL;
JSONArray users = null;
String TAG_ID = "id";
String TAG_NAME = "name";
String TAG_PHOTO = "photo";
String TAG_DATE = "date";
String TAG_DESC = "description";
ListView list;
NewsPromoAdapter newsAdapter;
boolean loadingMore = false;
private Runnable returnRes;
int itemsPerPage = 3;
int currentIndex = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.news_promo_listview);
list = (ListView) findViewById(R.id.mainView);
extras = getIntent().getExtras();
if (extras != null) {
user_points = extras.getInt("user_points");
user_email = extras.getString("user_email");
}
url = getString(R.string.app_url_news_promos);
npIDs = new ArrayList<Integer>();
npList = new ArrayList<NewsPromosDTO>();
View footerView = ((LayoutInflater) this
.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(
R.layout.footer, null, false);
newsAdapter = new NewsPromoAdapter(ListNewsPromoActivity.this, npList);
list.addFooterView(footerView);
list.setAdapter(newsAdapter);
list.setOnScrollListener(new OnScrollListener() {
// useless here, skip!
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// what is the bottom item that is visible
int lastInScreen = firstVisibleItem + visibleItemCount;
// is the bottom item visible & not loading more already ? Load
if ((lastInScreen == totalItemCount) && !(loadingMore)) {
Thread thread = new Thread(null, getRunnable());
thread.start();
}
}
});
// Runnable to load the items
// Since we cant update our UI from a thread this Runnable takes care of
// that!
returnRes = new Runnable() {
@Override
public void run() {
// Loop thru the new items and add them to the adapter
for (NewsPromosDTO np : npList) {
System.out.println(np.getName() + " andito ako!!");
newsAdapter.add(np);
}
newsAdapter.notifyDataSetChanged();
// Done loading more.
loadingMore = false;
}
};
}
protected class loadNewsPromo extends AsyncTask<Void, Void, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
protected String doInBackground(Void... params) {
// Creating JSON Parser instance
loadingMore = true;
JSONParser jParser = new JSONParser();
JSONObject json;
if (jParser.checkServer(url)) {
try {
// Getting Array of UserNews
json = jParser.getJSONFromUrl(url);
users = json.getJSONArray(user_email);
// looping through All UserNews
for (int i = currentIndex; i < itemsPerPage; i++) {
if (itemsPerPage == i) {
// currentIndex--;
break;
} else {
JSONObject c = users.getJSONObject(i);
// Storing each json item in variable
NewsPromosDTO npDTO = new NewsPromosDTO();
npDTO.setImageURL(c.getString(TAG_PHOTO));
npDTO.setId(c.getInt(TAG_ID));
npDTO.setName(c.getString(TAG_NAME));
npDTO.setDate(c.getString(TAG_DATE));
npDTO.setDescription(c.getString(TAG_DESC));
npList.add(npDTO);
currentIndex++;
}
}
} catch (JSONException e) {
e.printStackTrace();
return null;
} finally {
}
}
}
return null;
}
@Override
protected void onPostExecute(String result) { //
// progressDialog.dismiss();
loadingMore = false;
list();
}
}
public void list() {
// add the footer before adding the adapter, else the footer will not
// load!
View footerView = ((LayoutInflater) this
.getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(
R.layout.footer, null, false);
newsAdapter = new NewsPromoAdapter(ListNewsPromoActivity.this, npList);
list.addFooterView(footerView);
list.setAdapter(newsAdapter);
}
public Runnable getRunnable() {
Runnable loadMoreListItems = new Runnable() {
@Override
public void run() {
// Set flag so we cant load new items 2 at the same time
loadingMore = true;
// Reset the array that holds the new items
// Simulate a delay, delete this on a production environment!
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
// Get 15 new listitems
JSONParser jParser = new JSONParser();
JSONObject json;
npList = new ArrayList<NewsPromosDTO>();
if (jParser.checkServer(url)) {
try {
// Getting Array of Contacts
json = jParser.getJSONFromUrl(url);
users = json.getJSONArray(user_email);
// looping through All Contacts
// if (itemsPerPage > users.length() - currentIndex) {
// itemsPerPage = users.length();
// }
npList = new ArrayList<NewsPromosDTO>();
System.out.println(users.length() + " Laman ng users");
int counter = 0;
for (int i = currentIndex; i < users.length(); i++) {
if (itemsPerPage == counter) {
break;
} else {
JSONObject c = users.getJSONObject(i);
// Storing each json item in variable
NewsPromosDTO npDTO = new NewsPromosDTO();
npDTO.setImageURL(c.getString(TAG_PHOTO));
npDTO.setId(c.getInt(TAG_ID));
npDTO.setName(c.getString(TAG_NAME));
npDTO.setDate(c.getString(TAG_DATE));
npDTO.setDescription(c.getString(TAG_DESC));
npList.add(npDTO);
currentIndex++;
}
counter++;
}
} catch (JSONException e) {
e.printStackTrace();
} finally {
}
}
// Done! now continue on the UI thread
runOnUiThread(returnRes);
}
};
return loadMoreListItems;
}
}