1-主要活动：
public class MainActivity extends AppCompatActivity {
private List<String> mListItems = Arrays.asList("Hamaki","Amr Diab");
private ArtistsAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView listView = (ListView)findViewById(R.id.Artist_list_view);
mAdapter = new ArtistsAdapter(this, mListItems);
listView.setAdapter(mAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(MainActivity.this,SoundActivity.class);
intent.putExtra("Artist", mListItems.get(position));
startActivity(intent);
}
});
}
}
2-声音活动：
public class SoundActivity extends AppCompatActivity {
@Override
protected void onStart() {
super.onStart();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sound);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction().add(R.id.container, new SoundFragment()).commit();
}
}
3声片段：
public class SoundFragment extends Fragment {
static SCTrackAdapter mAdapter;
static DatabaseReference db;
static FirebaseHelper helper;
private TextView mSelectedTrackTitle;
static ArrayList<Music> mTracks = new ArrayList<>();
static MediaPlayer mMediaPlayer;
private ImageView mPlayerControl;
static String Artist;
static ListView listView;
int currentTrack;
private static String fileName;
public SoundFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public void onStart() {
super.onStart();
new Fetchtracks().execute();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_sound, container, false);
Intent intent = getActivity().getIntent();
if (intent != null) {
Artist = intent.getStringExtra("Artist");
}
listView = (ListView) rootView.findViewById(R.id.track_list_view);
mAdapter = new SCTrackAdapter(getActivity(), mTracks);
listView.setAdapter(mAdapter);
return rootView;
}
4-Strack适配器：
public class SCTrackAdapter extends BaseAdapter {
private Context mContext;
private ArrayList<Music> mTracks;
public SCTrackAdapter(Context context, ArrayList<Music> tracks) {
mContext = context;
mTracks = tracks;
}
public void update_tracks(ArrayList<Music> list)
{
mTracks.clear();
mTracks.addAll(list);
}
@Override
public int getCount() {
return mTracks.size();
}
@Override
public Music getItem(int position) {
return mTracks.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = LayoutInflater.from(mContext).inflate(R.layout.track_list_row, parent, false);
holder = new ViewHolder();
holder.titleTextView = (TextView) convertView.findViewById(R.id.track_title);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.titleTextView.setText(mTracks.get(position).getName());
return convertView;
}
static class ViewHolder {
TextView titleTextView;
}
}
5-提取轨迹：
公共类fetchtracks扩展了asynctask>{
@重写
protected ArrayList<Music> doInBackground(Void... voids) {
db = FirebaseDatabase.getInstance().getReference().child(Artist);
helper = new FirebaseHelper(db);
mTracks.addAll(helper.retrieve());
// Log.e("doInBackground: ",mTracks.size()+"");
return mTracks;
}
@Override
protected void onPostExecute(ArrayList<Music> list) {
super.onPostExecute(list);
Log.e("doInBackground: ",list.size()+"");
mAdapter.update_tracks(list);
mAdapter.notifyDataSetChanged();
listView.setAdapter(mAdapter);
}
}
6-FireBase助手：
公共类firebasehelper{
DatabaseReference db;
Boolean saved=null;
ArrayList<Music> A = new ArrayList<>();
public FirebaseHelper(DatabaseReference db) {
this.db = db;
}
//WRITE
public Boolean save(Music m)
{
if(m==null)
{
saved=false;
}else
{
try
{
// db.child(Artist).push().setValue(m);
saved=true;
}catch (DatabaseException e)
{
e.printStackTrace();
saved=false;
}
}
return saved;
}
//READ
public ArrayList<Music> retrieve()
{
A.clear();
db.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Log.e("onChildAdded: ", "1");
fetchData(dataSnapshot);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
Log.e("onChildAdded: ", "2");
fetchData(dataSnapshot);
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
// Log.e("onChildAdded: ", "3");
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
// Log.e("onChildAdded: ", "4");
}
@Override
public void onCancelled(DatabaseError databaseError) {
// Log.e("onChildAdded: ", "5");
}
});
return A;
}
private void fetchData(DataSnapshot dataSnapshot)
{
Music m=new Music();
m.setName(dataSnapshot.child("name").getValue().toString());
m.setUrl(dataSnapshot.child("url").getValue().toString());
A.add(m);
//soundfragment.mtracks.add（m）；
//log.e（“onfetch:”，soundfragment.mtracks.size（）+“”）；
}
}
7 -音乐：
public class Music {
String name;
String url;
public Music() {
}
public void setName(String name) {
this.name = name;
}
public void setUrl(String url) {
this.url = url;
}
public String getName() {
return name;
}
public String getURL() {
return url;
}
}
最佳答案
doInBackground()总是返回mTracks，该值在返回空列表之前未被修改！
您需要返回从helper.retrieve();接收的数据，并将数据传递到适配器！