我对此毫无希望！ 我试图找到4天内发生的事情..
基本上我从设备中取出所有歌曲并将它们显示在listView中。
listView位于一个名为MainFragment的简单片段中。
片段位于ViewPager内部，左右滑动选项。
listView和它的适配器在第一次初始运行时工作正常。
但是，在我的应用程序进入后台并且用户将应用程序带回到前面之后，listView没有被加载！ 这三行位于我使用listView和ArrayList：
启动适配器的位置 Log.d("Main Fragment", "Songs List View - " + String.valueOf(songsListView.getCount()));
Log.d("Main Fragment", "Songs List Adapter - " + String.valueOf(songListAdapter.getCount()));
Log.d("Main Fragment", "Songs List - " + String.valueOf(Constants.songList.size()));
他们都会在设备中返回正确数量的歌曲！
但在适配器内部，getView（）根本没有被调用。 我试图清除适配器'清除listView，清除歌曲列表，清除整个应用程序的整个布局！然后重新加载onResume（）.. 但似乎没有任何作用:(
MainFragment：
public class MainFragment extends Fragment {
public static boolean stopSearch = false;
public static ListView songsListView;
public ListView playListListView;
public PlayListListAdapter playeListAdapter;
public SongListAdapter songListAdapter;
public RelativeLayout play_list_container;
public Button cancelPlayList;
public Button okPlayList;
public Button chooseAll;
private View mRootView;@
Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
mRootView = inflater.inflate(R.layout.all_songs_layout, container,
false);
Log.w("Main Fragment", "Has been created");
return mRootView;
}
@
Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public void initLists() {
try {
if (songsListView == null) {
Log.d("Main Fragment", "initListView");
songsListView = (ListView) mRootView.findViewById(R.id.songsListView);
}
if (playListListView == null) {
playListListView = (ListView) mRootView.findViewById(R.id.playListListView);
play_list_container = (RelativeLayout) mRootView.findViewById(R.id.play_list_container);
}
} catch (NullPointerException e) {
Log.d("Main Fragment", "initLists " + e.toString());
}
}
public void onResume() {
try {
initLists();
} catch (NullPointerException e) {
songsListView = (ListView) mRootView.findViewById(R.id.songsListView);
playListListView = (ListView) mRootView.findViewById(R.id.playListListView);
play_list_container = (RelativeLayout) mRootView.findViewById(R.id.play_list_container);
}
//
Log.d("Main Fragment", "startSongsScan");
SongsHelper.getInstance().startSongsScan();
setOnClicks();
super.onResume();
}
private void setOnClicks() {
songsListView.setOnItemClickListener(new OnItemClickListener() {@
Override
public void onItemClick(AdapterView <? > parent, View arg1, int position, long var4) {
((Main) getActivity()).performListViewClick(position);
}
});
songsListView.setOnItemLongClickListener(new OnItemLongClickListener() {@
Override
public boolean onItemLongClick(AdapterView <? > parent, View arg1, int position, long var4) {
final Song song = (Song) parent.getItemAtPosition(position);
song.setCanDelete(true);
songListAdapter.notifyDataSetChanged();
return true;
}
});
chooseAll = (Button) mRootView.findViewById(R.id.chooseAll);
chooseAll.setOnClickListener(new OnClickListener() {@
Override
public void onClick(View v) {
((Main) getActivity()).initPlayListAllSongsSelected();
}
});
okPlayList = (Button) mRootView.findViewById(R.id.okPlayList);
okPlayList.setOnClickListener(new OnClickListener() {@
Override
public void onClick(View v) {
((Main) getActivity()).mPlayerUiHelper.savePlayList();
play_list_container.setVisibility(View.GONE);
songsListView.setVisibility(View.VISIBLE);
}
});
cancelPlayList = (Button) mRootView.findViewById(R.id.cancelPlayList);
cancelPlayList.setOnClickListener(new OnClickListener() {@
Override
public void onClick(View v) {
((Main) getActivity()).mPlayerUiHelper.cancelPlayList();
play_list_container.setVisibility(View.GONE);
songsListView.setVisibility(View.VISIBLE);
}
});
}
public void setListAdapter() {
if (songListAdapter == null) {
songListAdapter = new SongListAdapter(getActivity(), R.layout.song_row, Constants.songList);
songsListView.setAdapter(songListAdapter);
} else {
songListAdapter.notifyDataSetChanged();
}
if (songsListView == null || songsListView.getVisibility() == View.GONE) {
Log.d("Main Fragment", "Restart Views");
} else {
//Songs UI Helper
Log.d("Main Fragment", "Songs List View - " + String.valueOf(songsListView.getCount()));
Log.d("Main Fragment", "Songs List Adapter - " + String.valueOf(songListAdapter.getCount()));
Log.d("Main Fragment", "Songs List - " + String.valueOf(Constants.songList.size()));
}
}
}
SongListAdapter
public class SongListAdapter extends ArrayAdapter < Song > {
Context mContext;
int mResource;
List < Song > mSongs;
private ViewHolder holder;
public SongListAdapter(Context context, int resource, List < Song > objects) {
super(context, resource, objects);
this.mContext = context;
this.mResource = resource;
this.mSongs = objects;
try {
Comparator cp = Song.getComparator(Song.SortParameter.TITLE_ASCENDING);
Collections.sort(mSongs, cp);
} catch (Exception e) {
e.printStackTrace();
}
Log.d("Songs Adapter", "started");
Log.d("Songs Adapter", "Songs Count When Started - " + mSongs.size());
}
@
Override
public View getView(int position, View convertView, ViewGroup parent) {
final Song song = getItem(position);
Log.d("Songs Adapter", "getView");
Log.d("Songs Adapter", "Songs Count - " + mSongs.size());
Log.d("Songs Adapter", "Song - " + song.getTitle());
if (convertView == null) {
//create new view
convertView = LayoutInflater.from(getContext()).inflate(mResource, parent, false);
holder = new ViewHolder();
holder.songText = (ZenTextView) convertView.findViewById(R.id.songTitle);
holder.songArtist = (ZenTextView) convertView.findViewById(R.id.songArtist);
holder.songPhoto = (ImageView) convertView.findViewById(R.id.songIcon);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
//Set Artist Name
if (song.getArtist() != null && !song.getArtist().startsWith("<unknown>")) {
holder.songText.setText(song.getTitle());
holder.songArtist.setText(song.getArtist());
} else {
holder.songText.setText(song.getTitle());
holder.songArtist.setText(song.getArtist());
}
//Set Song image
setAlbumArt(song);
//Set item selected
holder.song_rl = (RelativeLayout) convertView.findViewById(R.id.song_rl);
if (song.isSelected() == true) {
holder.song_rl.setBackgroundResource(R.drawable.row_trans_back_selected);
} else {
holder.song_rl.setBackgroundResource(R.drawable.row_trans_back);
}
//Spinning record animation
if (song.isAnimationActive()) {
holder.songPhoto.startAnimation(
AnimationUtils.loadAnimation(getContext(), R.anim.rotate));
} else {
holder.songPhoto.clearAnimation();
}
//Set item for deletion
holder.deleteSong = (ImageView) convertView.findViewById(R.id.deleteFromList);
if (song.isCanDelete() == true) {
final int positionSelected = position;
holder.deleteSong.setVisibility(View.VISIBLE);
holder.deleteSong.setOnClickListener(new OnClickListener() {
@
Override
public void onClick(View v) {
Main.mPlayerUiHelper.showSpecialToast(mSongs.get(positionSelected).getTitle() + " Has Been Deleted..");
mSongs.remove(positionSelected);
notifyDataSetChanged();
notifyDataSetInvalidated();
}
});
} else
holder.deleteSong.setVisibility(View.GONE);
return convertView;
}
static class ViewHolder {
RelativeLayout song_rl;
ZenTextView songText;
ZenTextView songArtist;
ImageView songPhoto;
ImageView deleteSong;
}
private void setAlbumArt(Song song) {
if (song.getAlbumID() > 0) {
Uri artUri = ContentUris.withAppendedId(Uri.parse("content://media/external/audio/albumart"), song.getAlbumID());
try {
Picasso.with(mContext)
.load(artUri)
.error(R.drawable.list_image)
.into(holder.songPhoto);
} catch (IllegalArgumentException e) {
Picasso.with(mContext)
.load(R.drawable.list_image)
.into(holder.songPhoto);
}
}
}
@
Override
public int getCount() {
Log.d("Songs Adapter", "getCount() - " + mSongs.size());
return mSongs.size();
}
}
主要活动：
@
Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mainLayout = (RelativeLayout) findViewById(R.id.main_layout);
//For Phone Listening
Constants.mContext = this;
}
@
Override
protected void onResume() {
if (Constants.songList == null) {
Log.d("PlayerUiHelper", "songList was null..");
Constants.songList = new ArrayList < Song > ();
Constants.songListSearch = new ArrayList < Song > ();
Constants.songListShuffle = new ArrayList < Song > ();
}
Constants.activityOff = false;
initStartPlayer();
super.onResume();
}
public void initUIfromService() {
introPrefs = PreferenceManager.getDefaultSharedPreferences(Constants.mContext);
setViews();
initMediaControllersOnClicks();
initTabViews();
initMoreButton();
mPlayerUiHelper.setHeaderOnClicks();
//Start Service
Intent songIntent = new Intent(Main.this, SongsHelper.class);
startService(songIntent);
}
private void initStartPlayer() {
Constants.activityOff = false;
//Broadcast from service
LocalBroadcastManager bManager = LocalBroadcastManager.getInstance(Constants.mContext);
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(Constants.serviceBroadcastIntent);
bManager.registerReceiver(mServiceBroadcast, intentFilter);
//Start Songs Helper Service
Constants.mBackUpContentResolver = getContentResolver();
setEnglishLang();
mAnalytics = new AnalyticsHelper((AppumApplication) getApplication(),
getString(R.string.app_analytics_id), getString(R.string.app_name));
//Songs UI Helper
mPlayerUiHelper = PlayerUiHelper.getInstance();
tinydb = new TinyDB(Constants.mContext);
tinydb.putBoolean("restart_service", false);
utils = new Utilities();
initUIfromService();
Log.d(TAG, "Main Created");
}
public void setViews() {
Log.i(TAG, "Load Fragment Adapter");
if (fragMngr == null)
fragMngr = getSupportFragmentManager();
if (mPager != null) {
mPager.removeAllViews();
}
mPager = (ViewPager) findViewById(R.id.pager);
mPager.setOffscreenPageLimit(Constants.NUM_PAGES);
mPagerAdapter = new ScreenSlidePagerAdapter(fragMngr);
mPager.setAdapter(mPagerAdapter);
mPager.setOnPageChangeListener(new CustomCircularViewPagerHandler());
footer = (LinearLayout) findViewById(R.id.player_footer_bg);
//Play lists spinner
playListListView = (ListView) findViewById(R.id.playListListView);
listButton = (ImageView) findViewById(R.id.listButton);
initPlayLists();
albumCover = (ImageView) findViewById(R.id.albumCover);
songLabel = (ZenTextView) findViewById(R.id.songName);
albumName = (ZenTextView) findViewById(R.id.album_name);
songProgressBar = (SeekBar) findViewById(R.id.songProgressBar);
songCurrentDurationLabel = (ZenTextView) findViewById(R.id.songCurrentDurationLabel);
songTotalDurationLabel = (ZenTextView) findViewById(R.id.songTotalDurationLabel);
bypass = (ImageButton) findViewById(R.id.bypass);
// All player buttons
btnPlay = (ImageButton) findViewById(R.id.btnPlay);
btnNext = (ImageButton) findViewById(R.id.btnNext);
btnPrevious = (ImageButton) findViewById(R.id.btnPrevious);
btnRepeat = (ImageButton) findViewById(R.id.btnRepeat);
btnShuffle = (ImageButton) findViewById(R.id.btnShuffle);
prevButton = (ImageView) findViewById(R.id.prevButton);
prevButton.setOnClickListener(new View.OnClickListener() {
@
Override
public void onClick(View arg0) {
mPager.setCurrentItem(2);
}
});
nextButton = (ImageView) findViewById(R.id.nextButton);
nextButton.setOnClickListener(new View.OnClickListener() {
@
Override
public void onClick(View arg0) {
mPager.setCurrentItem(3);
}
});
}
此代码 - ** SongsHelper.getInstance（）。startSongsScan（）;正在扫描AsyncTask中的歌曲，它在onPoastExcecute（）之后加载ListView
拜托，拜托！帮我休息一下：）
答案 0 :(得分：0)
在initLists（）方法中调用setListAdapter（）;
答案 1 :(得分：0)
你应该在主onResume（）上创建和设置适配器和列表，并在完成AsyncTask并填充列表后，在适配器上调用notifyDataSetChanged。
答案 2 :(得分：0)
谢谢大家的回答和帮助！
我终于找到了解决方案。
完全清除每个片段使用的适配器：
try {
mainFragment.songListAdapter.clear();
mainFragment.songListAdapter = null;
} catch (NullPointerException e1) {
}
try {
albumSongListAdapter.clear();
albumSongListAdapter = null;
} catch (NullPointerException e1) {
}
try {
artistSongListAdapter.clear();
artistSongListAdapter = null;
} catch (NullPointerException e1) {
}
try {
albumGridAdapter.clear();
albumGridAdapter = null;
} catch (NullPointerException e1) {
}
try {
artistGridAdapter.clear();
artistGridAdapter = null;
} catch (NullPointerException e1) {
}
而不是改变这个：
if (songsListView == null) {
Log.d("Main Fragment", "initListView");
songsListView = (ListView) mRootView.findViewById(R.id.songsListView);
}
if (playListListView == null) {
playListListView = (ListView) mRootView.findViewById(R.id.playListListView);
play_list_container = (RelativeLayout) mRootView.findViewById(R.id.play_list_container);
}
到此：
songsListView = (ListView) mRootView.findViewById(R.id.songsListView);
playListListView = (ListView) mRootView.findViewById(R.id.playListListView);
play_list_container = (RelativeLayout) mRootView.findViewById(R.id.play_list_container);
显然，在ViewPager中的片段内使用listVies时，这是一个已知的错误。