我正在开发一个Android应用程序，它将从服务器服务获取最新消息，然后在列表视图中显示。代码如下：
HomeFragment.java
@SuppressLint("NewApi")
public class HomeFragment extends Fragment {
private ListView listView;
EditText search;
ImageButton btn;
ProgressDialog mProgressDialog;
private NewsHomeAdapter customNewsHomeAdapter;
Context homeFragmentContext;
final ArrayList<NewsItem> news_home_data = new ArrayList<NewsItem>();
// child categories JSONArray
JSONArray newsItems = null;
public HomeFragment(){}
@Override
public View onCreateView(LayoutInflater inflater, final ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_home, container, false);
homeFragmentContext = container.getContext();
listView = (ListView) rootView.findViewById(R.id.news_home_list);
search = (EditText) rootView.findViewById(R.id.search);
search.setOnKeyListener(new OnKeyListener() {
public boolean onKey(View v, int keyCode, KeyEvent event) {
if ((event.getAction() == KeyEvent.ACTION_DOWN)
&& (keyCode == KeyEvent.KEYCODE_ENTER)) {
String query_text = search.getText().toString().trim();
try {
query_text = URLEncoder.encode(query_text, "utf-8");
} catch (UnsupportedEncodingException e) {
}
String full_query = query_text;
InputMethodManager imm = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(search.getWindowToken(), 0);
Intent bussiness = new Intent(homeFragmentContext,
SearchNews.class);
Bundle basket_buss_category = new Bundle();
basket_buss_category.putString("SEARCH", full_query);
;
bussiness.putExtras(basket_buss_category);
startActivity(bussiness);
return true;
}
return false;
}
});
new GetNewsData().execute(TimeUtils.NEWS_HOME_URL);
listView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> a, View v, int position,
long id) {
Intent cluster = new Intent(homeFragmentContext, NewsCluster.class);
Bundle newslist = new Bundle();
newslist.putString("NLIST",news_home_data.get(position).getCluster());
cluster.putExtras(newslist);
startActivity(cluster);
}
});
btn = (ImageButton) rootView.findViewById(R.id.search_button);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
String query_text = search.getText().toString().trim();
if (query_text.equalsIgnoreCase("")) {
search.requestFocus();
InputMethodManager imm = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(search.getWindowToken(), 0);
}
else {
try {
query_text = URLEncoder.encode(query_text, "utf-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
String full_query = query_text;
InputMethodManager imm = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(search.getWindowToken(), 0);
Intent bussiness = new Intent(homeFragmentContext, SearchNews.class);
Bundle basket_buss_category = new Bundle();
basket_buss_category.putString("SEARCH", full_query);
bussiness.putExtras(basket_buss_category);
startActivity(bussiness);
}
}
});
return rootView;
}
private class GetNewsData extends
AsyncTask<String, Void, ArrayList<NewsItem>> {
protected void onPreExecute() {
super.onPreExecute();
// shfaq Progress Dialogun, deri ne momentin qe te loadohen te
// dheant
mProgressDialog = new ProgressDialog(homeFragmentContext);
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
mProgressDialog.show();
}
@Override
protected ArrayList<NewsItem> doInBackground(String... URL) {
String categories_url = URL[0];
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
newsItems = jParser.getJSONFromUrl(categories_url);
Log.e("lsbsfbsfdbsfd", newsItems.toString());
try {
for (int i = 0; i < newsItems.length(); i++) {
JSONObject c = newsItems.getJSONObject(i);
Log.e("po fillo procesimin e ", String.valueOf(i));
String tittle = c.getString(TimeUtils.TAG_TITLE);
String desc = c.getString(TimeUtils.TAG_DESC);
String source = c.getString(TimeUtils.TAG_SOURCE);
String id = c.getString(TimeUtils.TAG_ID);
String link = c.getString(TimeUtils.TAG_LINK);
String published_time = c.getString(TimeUtils.TAG_PUB_TIME);
String image_url = c.getString(TimeUtils.TAG_IMAGE_URL);
String newsList = c.getString(TimeUtils.TAG_CLUSTER);
// download the image;
Bitmap bitmap = null;
try { // Download Image from URL
InputStream input = new
java.net.URL(image_url) .openStream(); // Decode Bitmap
bitmap = BitmapFactory.decodeStream(input); } catch
(Exception e) {
}
news_home_data.add(new NewsItem(tittle, desc, source, id,
link, published_time, bitmap,newsList));
}
} catch (JSONException e) {
e.printStackTrace();
}
return news_home_data;
}
@SuppressLint("ResourceAsColor")
@Override
protected void onPostExecute(ArrayList<NewsItem> news_home_data) {
customNewsHomeAdapter = new NewsHomeAdapter(homeFragmentContext,
news_home_data);
listView.setAdapter(customNewsHomeAdapter);
// setting the nav drawer list adapter
mProgressDialog.dismiss();
}
}
适配器如下所示。
NesHomeAdapter.java
package com.dev.apk.time.al;
public class NewsHomeAdapter extends BaseAdapter{
private ArrayList<NewsItem> news_data;
private LayoutInflater layoutInflater;
public NewsHomeAdapter(Context context, ArrayList<NewsItem> news_data) {
this.news_data = news_data;
layoutInflater = LayoutInflater.from(context);
}
public int getCount() {
return news_data.size();
}
public Object getItem(int position) {
return news_data.get(position);
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = layoutInflater.inflate(R.layout.news_home_row, null);
holder = new ViewHolder();
holder.tittle = (TextView) convertView.findViewById(R.id.tittle);
holder.source = (TextView) convertView.findViewById(R.id.source);
holder.published_time = (TextView) convertView.findViewById(R.id.published_time);
holder.news_image = (ImageView) convertView.findViewById(R.id.news_image);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.tittle.setText(((NewsItem) news_data.get(position)).getTittle());
holder.source.setText(((NewsItem) news_data.get(position)).getSource());
holder.published_time.setText(((NewsItem) news_data.get(position)).getPublishedTime());
holder.news_image.setImageBitmap(((NewsItem) news_data.get(position)).getImage());
return convertView;
}
static class ViewHolder {
ImageView news_image;
TextView tittle;
TextView source;
TextView published_time;
}
}
因为我有自定义列表视图。对于每一行，我都有一个图像，该图像是根据来自JSON的URL下载的。但我第一次有至少40个新闻，意味着40张图片。显示新闻需要花费太多时间。
有人可以帮我如何同时下载图片，然后更新listView，还是有办法显示新闻，标题，描述等，然后更新图片？
答案 0 :(得分：0)
致电
UrlImageViewHelper.setUrlDrawable(yourImageView, "http://example.com/image.png", R.drawable.your_loading_image);
在您的适配器中，它将首先创建列表并稍后下载图像，当图像下载时，它将显示your_loading_image，下载的图像将很快显示
编辑：
确切地说，类NewsItem中的getImage（）函数返回的Image应该是图像的String url，并替换此行
holder.news_image.setImageBitmap(((NewsItem) news_data.get(position)).getImage());
到
UrlImageViewHelper.setUrlDrawable(holder.news_image, news_data.get(position).getImage(), R.drawable.your_loading_image);
我也遇到过这个问题，UrlImageViewHelper是解决这个问题的最简单的方法，只需导入库并使用一行就可以得到你想要的东西，不需要使用AsyncTask来加载图像来定义你自己的AsyncTask作为库本身
答案 1 :(得分：0)
我建议您在Android中使用AsyncTask。请查看http://developer.android.com/reference/android/os/AsyncTask.html
这将有助于您在后台运行并将您的进度或下载的图像发布到imageview上。
new AsyncTask<String,Void,Void>(){
@Override
protected Void doInBackground(String...arg){
//download the image against the url, and run in the background as not on UI thread.
}
@Override
protected void onPostExecute(Void v){
//Load the imageview with the downloaded image.
}
}.execute(url1,url2,url3);