SectionsPagerAdapter没有正确加载片段

时间:2015-11-19 17:53:54

标签: java android android-fragments tabs

我有一个Android活动,使用SectionsPagerAdapter显示3个标签,一个用于收到朋友请求,一个用于发送好友请求,一个用于当前好友。

当我打开活动时,它默认为选项卡0,即收到的请求,而是加载来自属于Friends片段的查询(使用parse.com)的结果。 Friends片段通常不显示任何内容,但它在后台运行Sent Request查询。转到“已发送”选项卡时,它会显示正确的选项卡。但是,当我返回其他任一选项卡时,有时它会显示其他选项卡下的“已发送请求”列表,或者根本没有显示任何内容,或者看似随机选择的三个选项卡中的一个。现在,这是我第一次使用选项卡式片段,所以我的问题可能就在那里,但是,我似乎无法找到它。

以下是包含标签的“好友”活动的代码:

public class FriendsActivity extends AppCompatActivity {


    private SectionsPagerAdapter mSectionsPagerAdapter;


    private ViewPager mViewPager;

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);


    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).
            switch(position){
                case 0 : return ReceivedFragment.newInstance();
                case 1 : return ConnectionsFragment.newInstance();
                case 2 : return SentFragment.newInstance();
            }
            return null;
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return getText(R.string.received);
                case 1:
                    return getText(R.string.friends);
                case 2:
                    return getText(R.string.sent);
            }
            return null;
        }
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_SECTION_NUMBER = "section_number";

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(int sectionNumber) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_NUMBER, sectionNumber);
            fragment.setArguments(args);
            return fragment;
        }

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_friends, container, false);
            TextView textView = (TextView) rootView.findViewById(R.id.section_label);
            textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }
    }
}

编辑:这是朋友列表片段的代码:

public class ConnectionsFragment extends Fragment{

    public static ConnectionsFragment newInstance() {
        ConnectionsFragment fragment = new ConnectionsFragment();
        return fragment;
    }

    public ConnectionsFragment()
    {

    }

    private SwipeMenuListView friendsListView;
    private ParseUser currentUser;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_connections, container, false);

        currentUser = ParseUser.getCurrentUser();
        friendsListView = (SwipeMenuListView) rootView.findViewById(R.id.friendsList);


        final ArrayList<SearchResults> searchResults = new ArrayList<SearchResults>();
        final ListAdapter listAdapter = new ListAdapter(getActivity(), searchResults);
        friendsListView.setAdapter(listAdapter);

        ParseQuery<ParseObject> senderQuery = ParseQuery.getQuery("FriendRequest");
        senderQuery.whereEqualTo("sender_id", currentUser.getObjectId());
        senderQuery.whereEqualTo("status", "accepted");
        ParseQuery<ParseObject> receiverQuery = ParseQuery.getQuery("FriendRequest");
        receiverQuery.whereEqualTo("receiver_id", currentUser.getObjectId());
        receiverQuery.whereEqualTo("status", "accepted");

        List<ParseQuery<ParseObject>> queries = new ArrayList<ParseQuery<ParseObject>>();
        queries.add(senderQuery);
        queries.add(receiverQuery);

        final ParseQuery<ParseObject> friendsQuery = ParseQuery.or(queries);

        friendsQuery.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(List<ParseObject> objects, ParseException e) {
                if (e == null) {
                    Log.d("USERS", "Retrieved " + objects.size() + " Users");
                    if (objects.size() > 0) {

                        for (ParseObject dealsObject : objects) {
                            ParseUser foundUser = null;
                            ParseQuery<ParseUser> query = ParseUser.getQuery();
                            try {
                                if (dealsObject.get("receiver_id") == currentUser.getObjectId())
                                {
                                    foundUser = query.get(dealsObject.getString("receiver_id"));
                                }
                                else
                                {
                                    foundUser = query.get(dealsObject.getString("sender_id"));
                                }
                                Log.i("NAME IN FRIENDSLIST", foundUser.getString("name"));
                            } catch (ParseException err) {
                                Log.e("ERROR", err.getMessage());
                            }

                            Log.i("NAME", foundUser.getString("name"));
                            final SearchResults sr1 = new SearchResults();
                            sr1.setName(foundUser.getString("name"));
                            sr1.setSurname1(foundUser.getString("surname1"));
                            sr1.setSurname2(foundUser.getString("surname2"));
                            sr1.setUid(foundUser.getObjectId());
                            Log.d("UID", foundUser.getObjectId());

                            sr1.setPhone(foundUser.getString("username"));
                            sr1.setEmail(foundUser.getString("email"));

                            ParseFile fileObject = (ParseFile) foundUser.get("thumbnail");
                            try {
                                byte[] imageBytes = fileObject.getData();
                                sr1.setImage(BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.length));
                            } catch (ParseException e1) {
                                Log.e("ERROR", e.getMessage());
                            }

                            searchResults.add(sr1);
                        }
                        listAdapter.notifyDataSetChanged();
                    } else if (objects.size() == 0) {
                        //Toast.makeText(getActivity(), R.string.no_search_results, Toast.LENGTH_LONG).show();
                    } else {
                        Log.e("USERS", "Error: " + e.getMessage());
                    }
                }
            }
        });

        friendsListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Object o = friendsListView.getItemAtPosition(position);
                SearchResults fullObject = (SearchResults) o;
                Intent i = new Intent(getActivity(),
                        UserDetailActivity.class);
                i.putExtra("uid", fullObject.getUid());
                startActivity(i);
            }
        });

        return rootView;
    }
}

1 个答案:

答案 0 :(得分:0)

内部

public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        switch(position){
            case 0 : return ReceivedFragment.newInstance();
            case 1 : return ConnectionsFragment.newInstance();
            case 2 : return SentFragment.newInstance();
        }
        return null;

每次滑动时,您都在创建每个片段的新实例。我建议在每个片段中使用onResume(),并在那里解析你的信息,以避免不必要的活动创建。

public static class RecievedFragment extends Fragment{

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){}

    public void onResume(){
        super.onResume();
        //Parse Info to this frag here
    }
}

并删除getItem()中的.newInstance()

public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        switch(position){
            case 0 : return ReceivedFragment;
            case 1 : return ConnectionsFragment;
            case 2 : return SentFragment;
        }
        return null;

我怀疑您的问题可能在于如何将数据解析为每个片段。你在使用一个共享变量吗?您可以发布代码,显示您在解析中的处理方式吗?