这是一个星期我试图解决这个问题成功。请帮帮我。
我使用带有viewpager的标签导航。这是我放置标签和FragmentPagerAdapter类的类：
public class Detail extends SherlockFragmentActivity {
ViewPager mViewPager;
TabsAdapter mTabsAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
...
ActionBar bar = getSupportActionBar();
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
bar.setDisplayOptions(0, ActionBar.DISPLAY_SHOW_TITLE);
mViewPager = (ViewPager)findViewById(R.id.pager);
// Add the tabs
mTabsAdapter = new TabsAdapter(this, bar, mViewPager);
mTabsAdapter.addTab(bar.newTab().setText(R.string.filmtab),
FragmentFilm.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.cinematab),
FragmentCinema.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.dintornitab),
FragmentPdi.class, null);
if (savedInstanceState != null) {
bar.setSelectedNavigationItem(savedInstanceState.getInt("tab"));
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("tab", getSupportActionBar().getSelectedNavigationIndex());
}
public static class TabsAdapter extends FragmentPagerAdapter
implements ViewPager.OnPageChangeListener, ActionBar.TabListener {
private final Context mContext;
private final ActionBar mBar;
private final ViewPager mViewPager;
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
static final class TabInfo {
private final Class<?> clss;
private final Bundle args;
TabInfo(Class<?> _class, Bundle _args) {
clss = _class;
args = _args;
}
}
public TabsAdapter(Detail activity, ActionBar bar, ViewPager pager) {
super(activity.getSupportFragmentManager());
mContext = activity;
mBar = bar;
mViewPager = pager;
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}
public void addTab(ActionBar.Tab tab, Class<? extends Fragment> clss, Bundle args) {
TabInfo info = new TabInfo(clss, args);
tab.setTag(info);
tab.setTabListener(this);
mTabs.add(info);
mBar.addTab(tab);
notifyDataSetChanged();
}
@Override
public int getCount() {
return mTabs.size();
}
@Override
public Fragment getItem(int position) {
TabInfo info = mTabs.get(position);
return Fragment.instantiate(mContext, info.clss.getName(), info.args);
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
mBar.setSelectedNavigationItem(position);
}
@Override
public void onPageScrollStateChanged(int state) {
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
Object tag = tab.getTag();
for (int i=0; i<mTabs.size(); i++) {
if (mTabs.get(i) == tag) {
mViewPager.setCurrentItem(i);
}
}
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
}
}
3个片段类都是一样的，我这里只复制一个; 在片段类中，我使用异步任务来下载我需要放在视图中的数据，我在onActivityCreated方法中执行此操作：
public class FragmentFilm extends SherlockFragment
{
private Detail act;
private DetailedRec detail_film;
private View view;
private String a;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
setRetainInstance(true);
view = inflater.inflate(R.layout.tab_film_info, container, false);
return view;
}
/*
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
act = (Detail) getActivity();
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
new DownloadFilmDetailAsyncTask().execute();
}
private class DownloadFilmDetailAsyncTask extends AsyncTask<Void, DetailedRec, Void>
{
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
ProgressBar prBar = (ProgressBar)getView().findViewById(R.id.progressbar_film);
prBar.setVisibility(View.GONE);
ScrollView lay = (ScrollView)getView().findViewById(R.id.tab_filmsummary);
lay.setVisibility(View.VISIBLE);
}
@Override
protected Void doInBackground(Void... params)
{
try
{
String locale = getResources().getConfiguration().locale.getDisplayName();
JSONObject objSend = new JSONObject();
objSend.put("idFilm", act.getIdFilm());
objSend.put("cinemaId",act.getIdCinema());
int ind = locale.indexOf("(");
String locale_send = locale.substring(0, ind-1);
objSend.put("locale", locale_send);
ArrayList<String> otherCin = new ArrayList<String>(Arrays.asList(act.getOtherCinemas()));
JSONArray othCin = new JSONArray(otherCin);
objSend.put("otherCinemas", othCin );
JSONObject jsonObject = sendAndGetJSONObject(JSON_SERVER+"JsonServer?op=getFilmbyId",objSend);
DetailedRec detail_rec = new DetailedRec();
//FILM
detail_rec.setFilmId(jsonObject.getString("filmId"));
detail_rec.setName(jsonObject.getString("name"));
detail_rec.setImageUrl(jsonObject.getString("imageUrl").replace("640", "80"));
detail_rec.setActors(jsonObject.getString("actors"));
detail_rec.setGenre(jsonObject.getString("genre"));
detail_rec.setDirector(jsonObject.getString("director"));
detail_rec.setPlot(jsonObject.getString("plot"));
detail_rec.setYear(jsonObject.getString("year"));
detail_rec.setDuration(jsonObject.getString("duration"));
detail_rec.setTrailer(jsonObject.getString("trailer"));
detail_rec.setRating(jsonObject.getString("rating"));
detail_film = detail_rec;
publishProgress(detail_rec);
}
catch (IOException ignored)
{
}
catch (JSONException ignored)
{
}
return null;
}
@Override
protected void onProgressUpdate(DetailedRec... values)
{
for (final DetailedRec detail_rec : values)
{
updateViews(detail_rec);
}
}
private JSONObject getJSONObject(String url) throws IOException, MalformedURLException, JSONException
{
HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
InputStream in = conn.getInputStream();
try
{
StringBuilder sb = new StringBuilder();
BufferedReader r = new BufferedReader(new InputStreamReader(new DoneHandlerInputStream(in),"WINDOWS_1252"));
for (String line = r.readLine(); line != null; line = r.readLine())
{
sb.append(line);
}
return new JSONObject(sb.toString());
}
finally
{
in.close();
}
}
private JSONObject sendAndGetJSONObject(String url,JSONObject request) throws IOException, MalformedURLException, JSONException
{
HttpClient client = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(client.getParams(), 10000); //Timeout Limit
InputStream in=null;
try{
HttpPost post = new HttpPost(url);
StringEntity se = new StringEntity(request.toString());
se.setContentType((Header) new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
post.setEntity(se);
HttpResponse response = client.execute(post);
HttpEntity entity = response.getEntity();
in = entity.getContent();
StringBuilder sb = new StringBuilder();
BufferedReader r = new BufferedReader(new InputStreamReader(new DoneHandlerInputStream(in),"WINDOWS_1252"));
for (String line = r.readLine(); line != null; line = r.readLine())
{
sb.append(line);
}
return new JSONObject(sb.toString());
}catch(Exception e){
}
finally
{
in.close();
}
return null;
}
}
private void updateViews(final DetailedRec detail_rec){
//FILM
TextView filmName = (TextView) getView().findViewById(R.id.movieTitle);
filmName.setText(detail_rec.getName().trim());
TextView actors = (TextView) getView().findViewById(R.id.movieActor);
actors.setText(detail_rec.getActors().trim());
TextView genre = (TextView) getView().findViewById(R.id.movieGenre);
genre.setText(detail_rec.getGenre().trim());
TextView director = (TextView) getView().findViewById(R.id.movieDirector);
director.setText(detail_rec.getDirector().trim());
TextView plot = (TextView) getView().findViewById(R.id.moviePlot);
plot.setText(detail_rec.getPlot().trim());
TextView year = (TextView) getView().findViewById(R.id.movieYear);
year.setText(detail_rec.getYear().trim());
TextView duration = (TextView) getView().findViewById(R.id.movieDuration);
duration.setText(detail_rec.getDuration().trim());
ImageView image = (ImageView) getView().findViewById(R.id.moviePoster);
new DownloadImagesTask(detail_rec.getImageUrl().trim().replace("80", "100")).execute(image);
//image.setImageBitmap(downloadBitmap(detail_rec.getImageUrl().trim().replace("80", "100")));
//Rating
if(detail_rec.getRating().compareTo("N/A")!=0){
RatingBar rateBar = (RatingBar)getView().findViewById(R.id.MovieRatingBar);
rateBar.setRating(Float.parseFloat(detail_rec.getRating()));
}
//Trailer
Button trailer = (Button)getView().findViewById(R.id.trailer);
if(detail_rec.getTrailer().compareTo("")!=0){
trailer.setVisibility(View.VISIBLE);
trailer.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
int index = detail_rec.getTrailer().indexOf("v=");
String videoId="";
if(index!=-1){
videoId = detail_rec.getTrailer().substring(index+2); //"Fee5vbFLYM4";
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("vnd.youtube:"+videoId));
intent.putExtra("VIDEO_ID", videoId);
startActivity(intent);
}
}
});
}
}
}
好的，在我的应用程序中，我希望片段加载一次。我解释得这么好： 当我启动Detail类时，片段类是istantiate并且所有3个片段中的AsyncTask开始，现在当用户从一个选项卡切换到另一个选项卡时我希望未选中选项卡中的片段不会丢失数据和视图，因为现在当我从一个选项卡切换到另一个选项卡，然后返回第一个重新创建的选项卡，再次调用onActivityCreated方法！
请帮助我，我在所有地方搜索，但我找不到解决方案!!
P.S。我使用SherlockActionBar，我不知道id是否相关。抱歉我的英文不好
谢谢
答案 0 :(得分：8)
在实例化ViewPager之后，添加此
mViewPager = (ViewPager)findViewById(R.id.pager);
mViewPager.setOffscreenPageLimit(3);
应该这样做！