Fragment中的Android ListView不顯示值

Question

我正在制作一個音樂應用程序，其中UI分為多個片段。 它基於TabbedActivty項目構建。 所以我的問題是：在MainActivity中，我正在將音樂文件從存儲加載到Array中。（那很好。）Array被傳遞給了一個輔助類。 然后，該Fragment加載該Array（也可以工作。）我可以設置適配器，但是即使該數組具有值，列表視圖也仍然為空。 我嘗試了很多代碼，但到目前為止沒有任何效果。 但是我沒有收到任何錯誤消息。

我的主要活動：

package needforbleed.com.music;

public class MainActivity extends AppCompatActivity {
    //vars
    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;
    private ArrayList<Song> songList;
    private ListView songView;
    private SongAdapter  songAdt;
    Context c;

    //methods
    @Override
    public void onAttachFragment(android.app.Fragment fragment) {
        super.onAttachFragment(fragment);
    }

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

        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);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        songList=new ArrayList<Song>();

        getSongList();



        c=this;

        Collections.sort(songList, new Comparator<Song>() {
            public int compare(Song a, Song b) {
                return a.getName().compareTo(b.getName());
            }
        });

        Helper.setSongs(songList);


      /*  for(int x=0;x<songList.size();x++)
        {



        }*/

       /* for(int x=0;x<songList.size();x++) {
            Toast toast = Toast.makeText(this,songList.get(x).getName(),Toast.LENGTH_SHORT);
            toast.show();

        }*///I used that loop to check songList for Content. It has content so that's not the error.
    }

    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.activity_main, container, false);
        return view;
    }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int position) {
           switch (position)
           {
               case 0:return Player.newInstance(0,"Player");
               case 1:return Artists.newInstance(1,"Artists");
               case 2:return Albums.newInstance(2,"Albums");
               case 3:return Titles.newInstance(3,"Titles");
           }

           return null;
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 4;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "Player";
                case 1:
                    return "Artists";
                case 2:
                    return "Albums";
                case 3:
                    return "Titles";
            }
            return null;
        }
    }

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

    @Override
    public void onAttachFragment(Fragment fragment) {
        super.onAttachFragment(fragment);

       /*songView=Helper.getLv();
        songAdt=new SongAdapter(this,songView.getId(),songList);
        songView.setAdapter(songAdt);
    */
    }

    public void getSongList() {
        ContentResolver musicResolver = getContentResolver();
        Uri musicUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);

        if(musicCursor!=null && musicCursor.moveToFirst()){
            //get columns
            int titleColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media.TITLE);

            int idColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media._ID);

            int artistColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media.ARTIST);

           int albumColumn=musicCursor.getColumnIndex(MediaStore.Audio.Media.ALBUM);
            //add songs to list
            do {
                long thisId = musicCursor.getLong(idColumn);
                String thisTitle = musicCursor.getString(titleColumn);
                String thisArtist = musicCursor.getString(artistColumn);
                String thisAlbum = musicCursor.getString(albumColumn);
                Song s=new Song();
                s.setID(thisId);
                s.setName(thisTitle);
                s.setArtist(thisArtist);
                s.setAlbum(thisAlbum);

                songList.add(s);
            }
            while (musicCursor.moveToNext());
        }
    }
}

MainActivity XML：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="needforbleed.com.music.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/appbar_padding_top"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"

            app:popupTheme="@style/AppTheme.PopupOverlay">

        </android.support.v7.widget.Toolbar>

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tabIndicatorColor="@color/tab_color"
            app:tabTextColor="@color/tab_color"
            app:tabSelectedTextColor="@color/colorPrimaryDark"
            />

    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="@dimen/fab_margin"
        android:src="@android:drawable/ic_dialog_email" />

</android.support.design.widget.CoordinatorLayout>

片段代碼：

package needforbleed.com.music;

/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link Titles.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link Titles#newInstance} factory method to
 * create an instance of this fragment.
 */
public class Titles extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "Number";
    private static final String ARG_PARAM2 = "Name";
    private ListView lv;
    private SongAdapter sa;

    // TODO: Rename and change types of parameters
    private int Number;
    private String Name;


    private OnFragmentInteractionListener mListener;

    public Titles() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment Titles.
     */
    // TODO: Rename and change types and number of parameters
    public static Titles newInstance(int param1, String param2) {
        Titles fragment = new Titles();
        Bundle args = new Bundle();
        args.putInt(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            Number = getArguments().getInt(ARG_PARAM1);
            Name = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View view = inflater.inflate(R.layout.fragment_titles, container, false);
        lv=(ListView)view.findViewById(R.id.lv_t);

        sa=new SongAdapter(this.getContext(),lv.getId(),Helper.getSongs());
        lv.setAdapter(sa);


        return inflater.inflate(R.layout.fragment_titles, container, false);
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p/>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name

        void onFragmentInteraction(Uri uri);
    }
}

片段XML

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="needforbleed.com.music.Titles">

    <!-- TODO: Update blank fragment layout -->

    <ListView
        android:layout_width="wrap_content"
        android:layout_height="523dp"
        android:id="@+id/lv_t"
        android:layout_gravity="left|top"
        android:smoothScrollbar="true" />
</FrameLayout>

助手類

package needforbleed.com.music;

public class Helper {
    private static SongAdapter s;
    private static ArrayList<Song> songs;
    private static ListView lv;

    public static ListView getLv() {
        return lv;
    }

    public static void setLv(ListView lv) {
        lv = lv;
    }

    public static ArrayList<Song> getSongs() {
        return songs;
    }

    public static void setSongs(ArrayList<Song> songs) {
        Helper.songs = songs;
    }

    public static SongAdapter getS() {
        return s;
    }

    public static void setS(SongAdapter s) {
        Helper.s = s;
    }
}

自定義適配器類

package needforbleed.com.music;

public class SongAdapter extends ArrayAdapter<Song> {

    public SongAdapter(Context context, int listviewid) {
        super(context, listviewid);
    }

    public SongAdapter(Context context, int resource, ArrayList<Song> tracks) {
        super(context, resource, tracks);
    }

    @Override
    public Song getItem(int position) {
        return super.getItem(position);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;

        if (v == null) {
            LayoutInflater vi;
            vi = LayoutInflater.from(getContext());
            v = vi.inflate(R.layout.title_list,parent,false);
        }

        Song p = getItem(position);

        if (p != null) {
            TextView tt1 = (TextView) v.findViewById(R.id.song_title);
            TextView tt2 = (TextView) v.findViewById(R.id.song_artist);
            TextView tt3 = (TextView) v.findViewById(R.id.song_album);

            if (tt1 != null) {
                tt1.setText(p.getName());
            }

            if (tt2 != null) {
                tt2.setText(p.getArtist());
            }

            if (tt3 != null) {
                tt3.setText(p.getAlbum());
            }
        }

        return v;
    }
}

title_list xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:onClick="songPicked"
    android:orientation="vertical"
    android:padding="5dp" >

    <TextView
        android:id="@+id/song_title"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textColor="@color/colorAccent"
        android:textSize="22sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/song_artist"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="20sp" />
    <TextView
        android:id="@+id/song_album"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textColor="#000000"
        android:textSize="18sp" />

</LinearLayout>

顏色XML

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="colorPrimary">#f08320</color>
    <color name="colorPrimaryDark">#d76e0e</color>
    <color name="colorAccent">#f08320</color>
    <color name="tab_color">#ffffff</color>
    <color name="nav_bar">#f08320</color>

</resources>

Answer 1

在片段返回view中的on create視圖中，而不是

inflater.inflate(R.layout.fragment_titles, container, false);

Answer 2

在onCreateView方法中，您將返回新的展開視圖。

應該是這樣的：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment

    View view = inflater.inflate(R.layout.fragment_titles, container, false);
    lv=(ListView)view.findViewById(R.id.lv_t);

    sa=new SongAdapter(this.getContext(),lv.getId(),Helper.getSongs());
    lv.setAdapter(sa);

    return view;
}