Question

我有一个ViewPager在Activity中使用FragmentStatePagerAdapter，它必须显示3个片段，现在只实现了第一个片段。第一个片段使用asyncTask获取类别列表并在ListView中显示它们。

Here's the view we get of the fragment

ViewPager使用FragmentPagerAdapter来显示项目。

问题出现在用户点击标签栏上的按钮以返回第一个活动时。我们第二次使用片段进行活动时，我无法更新视图，有一个我更新的ListView和ProgressBar，我调用setVisibility但没有任何反应。

The loader keeps displayed even if I call setVisibility(View.INVISIBLE)

为什么视图只是第一次更新？

包含ViewPager的活动：

public class BoutiqueActivity extends AppCompatActivity {

protected ViewPager viewPager;
protected TabLayout tabLayout;
protected Bundle savedInstanceState;
protected ViewPagerAdapter adapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_boutique);

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    this.viewPager = this.findViewById(R.id.viewPager);
    this.viewPager.setSaveFromParentEnabled(false);
    this.savedInstanceState = savedInstanceState;
    this.adapter = new ViewPagerAdapter(getSupportFragmentManager());

    if (savedInstanceState == null){
        this.setupViewPager();
    }else {
        Integer count = savedInstanceState.getInt("tabsCount");
        String[] titles = savedInstanceState.getStringArray("titles");
        for (int i = 0; i < count; i++) {
            this.adapter.addFragment(getFragment(i), titles[i]);
        }
    }

}

@Override
public void onStart(){
    super.onStart();

    viewPager.setAdapter(adapter);

    this.tabLayout = this.findViewById(R.id.tabLayout);
    this.tabLayout.setupWithViewPager(viewPager);
}

private Fragment getFragment(int position){
    return savedInstanceState == null ? adapter.getItem(position) : getSupportFragmentManager().findFragmentByTag(getFragmentTag(position));
}

private String getFragmentTag(int position) {
    return "android:switcher:" + R.id.viewPager + ":" + position;
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt("tabsCount", adapter.getCount());
    outState.putStringArray("titles", adapter.getFragmentTitles().toArray(new String[0]));
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();


    if(id == android.R.id.home) {
        this.finish();
    }

    return super.onOptionsItemSelected(item);
}

private void setupViewPager() {
    this.adapter.addFragment(new CategorieFragment(), "Catégories");
    this.adapter.addFragment(new ArticleFragment(), "Articles");
    this.adapter.addFragment(new PromotionFragment(), "Promotions");
}}

片段：

public class CategorieFragment extends Fragment implements ActiviteEnAttenteAvecResultat<Categorie> {

protected ArrayList<Categorie> categories;

protected ListView listView;
protected Drawable substitut;
protected ProgressBar loader;

public CategorieFragment(){};

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstance){
    View view = inflater.inflate(R.layout.fragment_categorie, null);

    try {
        this.substitut = Drawable.createFromStream(getActivity().getAssets().open("cintre.png"), null);
    } catch (IOException e){}

    return view;
}

@Override
public void onCreate(Bundle savedInstance){
    super.onCreate(savedInstance);
    this.categories = new ArrayList<>();
}

@Override
public void onStart(){
    super.onStart();
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    this.listView = view.findViewById(R.id.liste);
    this.loader = view.findViewById(R.id.loader);

    CategorieAdapter categorieAdapter = new CategorieAdapter(getActivity(), categories, substitut);
    this.listView.setAdapter(categorieAdapter);

    CategorieDAO.getInstance(this, this.loader, this.listView).findAll();
}

@Override
public void notifyRetourRequete(Categorie result){

}

@Override
public void notifyRetourRequeteFindAll(ArrayList<Categorie> liste){
    this.categories.clear();
    this.categories.addAll(liste);

    ((BaseAdapter) this.listView.getAdapter()).notifyDataSetChanged();
}

@Override
public void afficheLoader(){
    this.loader.setVisibility(View.VISIBLE);
    this.listView.setVisibility(View.INVISIBLE);
}

@Override
public void cacheLoaderAfficheContenu() {
    this.loader.setVisibility(View.INVISIBLE);
    this.listView.setVisibility(View.VISIBLE);
}}

适配器：

public class ViewPagerAdapter extends FragmentStatePagerAdapter {

protected final List<Fragment> fragmentList = new ArrayList<>();
protected final List<String> fragmentTitleList = new ArrayList<>();

public ViewPagerAdapter(FragmentManager manager){
    super(manager);
}

@Override
public Fragment getItem(int position) {
    return fragmentList.get(position);
}

@Override
public int getCount() {
    return fragmentList.size();
}

@Override
public CharSequence getPageTitle(int position){
    return fragmentTitleList.get(position);
}

public void addFragment(Fragment fragment, String title){
    fragmentList.add(fragment);
    fragmentTitleList.add(title);
}

public List<String> getFragmentTitles(){
    return this.fragmentTitleList;
}}

的AsyncTask

public class HTTPRequest<T extends Object> extends AsyncTask<String, Void, String> {

protected ProgressBar loader;
protected ListView listView;

protected ActiviteEnAttenteAvecResultat activite;
protected DAO dao;

protected String method;
protected String error;
protected Object data;
protected Class deserializationClass;

public HTTPRequest(ActiviteEnAttenteAvecResultat activite, DAO dao, String method, Object data, Class deserializationClass, ProgressBar loader, ListView listView){
    this.activite = activite;
    this.dao = dao;
    this.method = method;
    this.data = data;
    this.deserializationClass = deserializationClass;
    this.loader = loader;
    this.listView = listView;
}

public HTTPRequest(ActiviteEnAttenteAvecResultat activite, DAO dao, String method, Object data, Class deserializationClass){
    this.activite = activite;
    this.dao = dao;
    this.method = method;
    this.data = data;
    this.deserializationClass = deserializationClass;
}

@Override
protected void onPreExecute(){
    this.afficheLoader();
}

@Override
protected String doInBackground(String... urls) {
    String urlRequete = urls[0];
    StringBuffer resultat = new StringBuffer(1024);
    try{
        final HttpURLConnection connection = (HttpURLConnection) new URL(urlRequete).openConnection();
        connection.setReadTimeout(1000);
        connection.setConnectTimeout(1500);
        connection.setRequestMethod(this.method);
        connection.setDoInput(true);

        connection.connect();
        InputStream input = connection.getInputStream();

        BufferedReader in = new BufferedReader(new InputStreamReader(input));
        String line = "";
        while((line = in.readLine()) != null){
            resultat.append(line);
        }
        in.close();

    } catch (Exception e){
        this.error = "Error : " + e.getMessage();
        return null;
    }

    return resultat.toString();
}

@Override
protected void onPostExecute(String result){
    Gson gson = new Gson();
    ArrayList<T> liste = new ArrayList<>();

    if(result != null){
        switch (this.method){
            case (HTTPRequestMethod.GET):
                JsonParser parser = new JsonParser();
                JsonArray array = parser.parse(result).getAsJsonArray();
                for (int i = 0; i < array.size(); i++) {
                    Object object = gson.fromJson(array.get(i), this.deserializationClass);
                    liste.add((T) object);
                }

                activite.notifyRetourRequeteFindAll(liste);
                break;
        }
    } else {

    }

    this.cacheLoaderAfficheContenu();
}

public void afficheLoader(){
    this.loader.setVisibility(View.VISIBLE);
    this.listView.setVisibility(View.INVISIBLE);
}

public void cacheLoaderAfficheContenu() {
    this.loader.setVisibility(View.INVISIBLE);
    this.listView.setVisibility(View.VISIBLE);
}}

ViewPager中使用FragmentStatePagerAdapter的片段在第二次查看时为空白

0 个答案: