我在viewPager中使用相同片段的不同实例。因为每个页面都做同样的事情，但只是数据不同。但问题是viewPager在所有页面中显示相同的数据。在适配器中创建新实例不会改变数据。我想要的是当用户滑动到新页面时，它会显示相应片段的新实例，如同适配器中显示的位置一样。
这是适配器：
public class FragmentPageAdapter extends FragmentPagerAdapter {
public FragmentPageAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
if (position == 0) {
ListViewFragment f = ListViewFragment.newInstance("https://newsapi.org/v1/articles?source=al-jazeera-english&sortBy=top&apiKey=6cde");
return f;
}
else if (position == 1){
return ListViewFragment.newInstance("https://newsapi.org/v1/articles?source=abc-news-au&sortBy=top&apiKey=6cde");
}
else
{
return ListViewFragment.newInstance("https://newsapi.org/v1/articles?source=bbc-news&sortBy=top&apiKey=6cde");
}
}
@Override
public int getCount() {
return 3;
}
}
此活动包含viewPager：
public class WorldNews extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_world_news);
// Find the view pager that will allow the user to swipe between fragments
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
// Create an adapter that knows which fragment should be shown on each page
FragmentPageAdapter adapter = new FragmentPageAdapter(getSupportFragmentManager());
// Set the adapter onto the view pager
viewPager.setAdapter(adapter);
}
}
这是Fragment的代码（只是一个实现loader的普通片段）：
public class ListViewFragment extends Fragment implements LoaderManager.LoaderCallbacks<List<GameNews>> {
public static ListViewFragment newInstance(String url) {
Log.d("ListViewFragment","newInstance created");
ListViewFragment f = new ListViewFragment();
// Supply url input as an argument.
Bundle args = new Bundle();
args.putString("url", url);
f.setArguments(args);
return f;
}
private AdView mAdView;
AdRequest adRequest;
ListAdapter adapter ;
private View progressBar;
final private int game_loader = 0;
ArrayList<String> urls = new ArrayList<>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_list_view, container, false);
//Log.d("ListViewFragment","" + getArguments().getString("url"));
mAdView = (AdView) rootView.findViewById(R.id.adView);
adRequest = new AdRequest.Builder().build();
mAdView.loadAd(adRequest);
final LinearLayout emptyView = (LinearLayout) rootView.findViewById(R.id.no_internet_view);
emptyView.setVisibility(View.INVISIBLE);
//Getting listView
final ListView gameListView = (ListView) rootView.findViewById(R.id.listView);
//progress bar finding
progressBar = rootView.findViewById(R.id.progress_bar);
ArrayList<GameNews> gameList = new ArrayList<>();
Button retryButton = (Button) rootView.findViewById(R.id.retry_button);
//Making a new arrayAdapter
adapter = new ListAdapter(getActivity(),gameList);
//Connecting ArrayAdapter to ListView
gameListView.setAdapter(adapter);
urls.add(getArguments().getString("url"));
Log.d("ListViewFragment","" + urls.get(0));
if(isConnected())
{
getActivity().getLoaderManager().initLoader(game_loader, null, this);
}
else
{
emptyView.setVisibility(View.VISIBLE);
gameListView.setVisibility(View.INVISIBLE);
}
//ListView item click listner
gameListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
GameNews currentEarthquake = adapter.getItem(i);
String url = currentEarthquake.getUrl();
final Intent intent = new Intent(getContext(), browser.class);
intent.putExtra("Url", url);
startActivity(intent);
}
});
retryButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(isConnected())
{
mAdView.loadAd(adRequest);
getActivity().getLoaderManager().restartLoader(game_loader, null, ListViewFragment.this);
emptyView.setVisibility(View.INVISIBLE);
gameListView.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.VISIBLE);
Log.d("General news","retry clicked");
}
}
});
return rootView;
}
public boolean isConnected() {
ConnectivityManager manager = (ConnectivityManager)getActivity().getSystemService(CONNECTIVITY_SERVICE);
NetworkInfo info = manager.getActiveNetworkInfo();
if (info != null && info.isConnected()) {
return true;
} else {
return false;
}
}
@Override
public Loader<List<GameNews>> onCreateLoader(int i, Bundle bundle) {
AdManager manager = new AdManager(getActivity());
return new GameLoader(getActivity(),urls,1000);
}
@Override
public void onLoadFinished(Loader<List<GameNews>> loader, List<GameNews> games) {
progressBar.setVisibility(View.INVISIBLE);
adapter.clear();
if(games == null)
{
return;
}
adapter.addAll(games);
}
@Override
public void onLoaderReset(Loader<List<GameNews>> loader) {
adapter.clear();
}
public void setUrl(String url)
{
this.urls.add(url);
}
}
答案 0 :(得分：0)
尝试使用FragmentStatePagerAdapter https://developer.android.com/reference/android/support/v4/app/FragmentStatePagerAdapter代替FragmentPagerAdapter。它们之间的区别：例如here。