Android如何丰富arraylist
问题描述:
我正在制作一个3片段页面应用程序,它的第一个片段是从http加载json,但是当我转到fragment3并返回到fragment1时,它将消失并从http再次加载它。我如何正确设置片段中的保存/恢复状态。Android如何丰富arraylist
片段1代码:
public class Fragment1 extends Fragment {
private ArrayList<FeedItem> feedList = null;
private ProgressBar progressbar = null;
private ListView feedListView = null;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_post_list, container, false);
progressbar = (ProgressBar)rootView.findViewById(R.id.progressBar);
String url = "";
new DownloadFilesTask().execute(url);
return rootView;
}
public void updateList() {
feedListView= (ListView)getActivity().findViewById(R.id.custom_list);
feedListView.setVisibility(View.VISIBLE);
if (progressbar.isShown()) {
progressbar.setVisibility(View.GONE);
}
feedListView.setAdapter(new CustomListAdapter(getActivity(), feedList));
feedListView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
Object o = feedListView.getItemAtPosition(position);
FeedItem newsData = (FeedItem) o;
Intent intent = new Intent(getActivity(), FeedDetailsActivity.class);
intent.putExtra("feed", newsData);
startActivity(intent);
}
});
}
public class DownloadFilesTask extends AsyncTask<String, Integer, Void> {
@Override
protected void onProgressUpdate(Integer... values) {
}
@Override
protected void onPostExecute(Void result) {
if (null != feedList) {
updateList();
}
}
@Override
protected Void doInBackground(String... params) {
String url = params[0];
// getting JSON string from URL
JSONObject json = getJSONFromUrl(url);
//parsing json data
parseJson(json);
return null;
}
}
public JSONObject getJSONFromUrl(String url) {
InputStream is = null;
JSONObject jObj = null;
String json = null;
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
public void parseJson(JSONObject json) {
try {
// parsing json object
if (json.getString("status").equalsIgnoreCase("ok")) {
JSONArray posts = json.getJSONArray("posts");
feedList = new ArrayList<FeedItem>();
for (int i = 0; i < posts.length(); i++) {
JSONObject post = (JSONObject) posts.getJSONObject(i);
FeedItem item = new FeedItem();
item.setTitle(post.getString("title"));
item.setDate(post.getString("description"));
item.setId(post.getString("id"));
item.setUrl(post.getString("url"));
item.setContent(post.getString("description"));
item.setInfoz(post.getString("description"));
JSONArray attachments = post.getJSONArray("attachments");
if (null != attachments && attachments.length() > 0) {
JSONObject attachment = attachments.getJSONObject(0);
if (attachment != null)
item.setAttachmentUrl(attachment.getString("url"));
}
feedList.add(item);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
答
很简单:你可以重写方法onSaveInstanceState(bundle outState)
和保存要到outState
任何状态。然后,在onCreateView()
您可以阅读状态(如果有的话 - 它可能和将是无效首次启动时)从对象savedInstanceState
,
我已经加入此@Override \t公共无效的onSaveInstanceState(捆绑outState){ \t超.onSaveInstanceState(outState); (“feedList”,(ArrayList )feedList);}};}}};}} \t} and this to oncreateview feedList = savedInstanceState.getParcelableArrayList(“feedList”);但我得到错误绑定不匹配:类型Bundle的泛型方法getParcelableArrayList(String)不适用于参数(字符串)。推断的类型FeedItem不是有界参数的有效替代 –
@SandraMladenovic您需要使FeedItem实现Parcelable才能使用putParcelable()方法 - 请参阅http://developer.android.com/reference/android /os/Parcelable.html – ddmps
但我已经公开课FeedItem实现Serializable,我不能实现和Parcelable,现在呢? –