我想创建一个包含2个项目的ViewPager，每个视图都包含listview。当我从一个页面刷到另一个页面时，每次listview都会刷新。我只需刷新一次。意味着如果一旦加载值列表视图，那么我刷到下一页它不需要再次重新加载。我需要向列表视图显示已加载的值
码
public class ViewpagerAdapter extends FragmentPagerAdapter {
private Context _context;
public static int totalPage=2;
public ViewpagerAdapter(Context applicationContext,
android.support.v4.app.FragmentManager fragmentManager) {
super(fragmentManager);
_context=applicationContext;
}
@Override
public Fragment getItem(int position) {
Fragment f = new Fragment();
switch(position){
case 0:
f= FirstFragment.newInstance(_context);
break;
case 1:
f= SecondFragment.newInstance(_context);
break;
}
return f;
}
@Override
public int getCount() {
return totalPage;
}}
FirstFragment
public class FirstFragment extends Fragment {
private Context context;
private List<Historyitem> historyitems;
HistoryRecycleListAdapter historyadapter;
Handler mHandler;
ListView hisrecyclerview;
public static Fragment newInstance(Context context) {
FirstFragment f = new FirstFragment();
return f;
}
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
ViewGroup view = (ViewGroup) inflater.inflate(R.layout.firstfragment, null);
context = getActivity();
hisrecyclerview = (ListView)view.findViewById(R.id.hisrecyclerview);
LoadHistoryInitiate();
return view;
}
public void LoadHistoryInitiate() throws IllegalStateException{
new AsyncTask<String, String, String>(){
protected void onPreExecute() {
historyitems = new ArrayList<Historyitem>();
historyitems.clear();
};
@Override
protected String doInBackground(String... arg0) {
final List<NameValuePair> list=new ArrayList<NameValuePair>();
list.add(new BasicNameValuePair("id", id));
final HttpParams httpParams = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(httpParams, 30000);
DefaultHttpClient httpClient = new DefaultHttpClient(httpParams);
HttpPost httpPost = new HttpPost(url);
httpPost.getParams().setBooleanParameter(CoreProtocolPNames.USE_EXPECT_CONTINUE, false);
try {
httpPost.setEntity(new UrlEncodedFormEntity(list));
} catch (IOException e) {
e.printStackTrace();
}
try {
HttpResponse response = httpClient.execute(httpPost);
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
String json = reader.readLine();
JSONObject jsonObj = new JSONObject(json);
if(jsonObj.has("values")){
JSONArray feedArray = jsonObj.getJSONArray("values");
for (int i = 0; i < feedArray.length(); i++) {
JSONObject feedObj = (JSONObject) feedArray.get(i);
final Historyitem item = new Historyitem();
if(feedObj.has("Reported_Time")){
if(!feedObj.getString("Reported_Time").replaceAll(" ", "").equals("")){
item.setReported_Time(feedObj.getString("Reported_Time"));
}
}
historyitems.add(item);
}
}else{
}
} catch (JSONException e) {
e.printStackTrace();
} catch(NullPointerException e){
e.printStackTrace();
} catch (SocketException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String result) {
System.out.println(historyitems.size());
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
historyadapter = new HistoryRecycleListAdapter(getActivity(), getActivity(),historyitems);
hisrecyclerview.setAdapter(historyadapter);
hisrecyclerview.addFooterView(btnLoadMore);
hisrecyclerview.setAdapter(historyadapter);
}
}, 1000);
};
}.execute();
} }
第二片段
public class SecondFragment extends Fragment {
private Context context;
private List<Loaditem> loaditems;
RecycleListAdapter loadadapter;
Handler mHandler;
ListView recyclerview;
public static Fragment newInstance(Context context) {
SecondFragment f = new SecondFragment();
return f;
}
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
ViewGroup view = (ViewGroup) inflater.inflate(R.layout.secondfragment, null);
context = getActivity();
recyclerview = (ListView)view.findViewById(R.id.recyclerview);
LoadInitiate();
return view;
}
public void LoadInitiate() throws IllegalStateException{
new AsyncTask<String, String, String>(){
protected void onPreExecute() {
loaditems = new ArrayList<Loaditem>();
loaditems.clear();
};
@Override
protected String doInBackground(String... arg0) {
final List<NameValuePair> list=new ArrayList<NameValuePair>();
list.add(new BasicNameValuePair("uid", uid));
final HttpParams httpParams = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(httpParams, 30000);
DefaultHttpClient httpClient = new DefaultHttpClient(httpParams);
HttpPost httpPost = new HttpPost(url);
httpPost.getParams().setBooleanParameter(CoreProtocolPNames.USE_EXPECT_CONTINUE, false);
try {
httpPost.setEntity(new UrlEncodedFormEntity(list));
} catch (IOException e) {
e.printStackTrace();
}
try {
HttpResponse response = httpClient.execute(httpPost);
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
String json = reader.readLine();
JSONObject jsonObj = new JSONObject(json);
if(jsonObj.has("values")){
JSONArray feedArray = jsonObj.getJSONArray("values");
for (int i = 0; i < feedArray.length(); i++) {
JSONObject feedObj = (JSONObject) feedArray.get(i);
final Loaditem item = new Loaditem();
if(feedObj.has("Time")){
if(!feedObj.getString("Time").replaceAll(" ", "").equals("")){
item.setReported_Time(feedObj.getString("Time"));
}
}
loaditems.add(item);
}
}else{
}
} catch (JSONException e) {
e.printStackTrace();
} catch(NullPointerException e){
e.printStackTrace();
} catch (SocketException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String result) {
System.out.println(historyitems.size());
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
loadadapter = new RecycleListAdapter(getActivity(), getActivity(),loaditems);
recyclerview.addFooterView(btnLoadMore);
recyclerview.setAdapter(loadadapter);
}
}, 1000);
};
}.execute();
} }
答案 0 :(得分：0)
最简单的解决方案是setOffscreenPageLimit(int limit)将其设置为viewPager。
答案 1 :(得分：0)
要解决您的问题，请在您的活动中使用以下方法：
setOffscreenPageLimit(int limit)
Set the number of pages that should be retained to either side of the current page in the view hierarchy in an idle state.
在ViewPager实例化后添加以下行
viewpager.setOffscreenPageLimit(2)