我一直在尝试使用PlaylistsAdapter创建ListView。但每当我尝试点击imgCoverArt时，应用程序就会崩溃，说明歌曲列表的大小为0。我试着改变了变量的类型，只是整体上改变了代码。但我就是解决不了，我也不知道这个问题。
提前谢谢。
这就是我得到的错误：
2020-08-10 03:52:56.720 3091-3091/sg.edu.tp.musicstream E/AndroidRuntime: FATAL EXCEPTION: main
Process: sg.edu.tp.musicstream, PID: 3091
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.get(ArrayList.java:437)
at sg.edu.tp.musicstream.PlaylistsAdapter$1.onClick(PlaylistsAdapter.java:88)
at android.view.View.performClick(View.java:6294)
at android.view.View$PerformClick.run(View.java:24770)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
我已经试着把相关的课程包括在内，如果你还需要什么，请告诉我。
package sg.edu.tp.musicstream;
import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageButton;
import android.widget.TextView;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import sg.edu.tp.musicstream.util.AppUtil;
public class PlaylistsAdapter extends BaseAdapter {
Context mContext;
LayoutInflater inflater;
Song[] songs;
List<Song> songlist;
ArrayList<Song> arrayList;
public PlaylistsAdapter(Context context, List<Song> songlist, Song[] songs)
{
mContext = context;
inflater = LayoutInflater.from(mContext);
this.songs = songs;
this.songlist = songlist;
this.arrayList = new ArrayList<>();
this.arrayList.addAll(songlist);
}
public class ViewHolder
{
ImageButton imgCoverArt;
TextView txtSongTitle;
TextView txtArtist;
ImageButton btnAddToPlaylist;
}
@Override
public int getCount() {
return songlist.size();
}
@Override
public Object getItem(int position) {
return songlist.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
holder = new ViewHolder();
convertView = inflater.inflate(R.layout.playlist_listview, null);
holder.imgCoverArt = convertView.findViewById(R.id.imgCoverArt);
holder.txtSongTitle = convertView.findViewById(R.id.txtSongTitle);
holder.txtArtist = convertView.findViewById(R.id.txtArtist);
holder.btnAddToPlaylist = convertView.findViewById(R.id.btnAddToPlaylist);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.imgCoverArt.setImageResource(songlist.get(position).getCoverArt());
holder.imgCoverArt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
for (int index = 0; index < songs.length; index++)
{
if (songlist.get(position).getId().equals(songs[index].getId())) {
Song song = songs[index];
sendDataToActivity(songs, song);
AppUtil.popMessage(mContext, ""+ songlist.size());
}
}
}
});
holder.txtSongTitle.setText(songlist.get(position).getTitle());
holder.txtArtist.setText(songlist.get(position).getArtist());
if (position >= 10) {
holder.btnAddToPlaylist.setContentDescription("S10" + position);
} else {
holder.btnAddToPlaylist.setContentDescription("S100" + position);
}
return convertView;
}
public void sendDataToActivity(Song[] songs, Song song)
{
// 1. Create a new Intent and specify the source and destination screen/activity.
Intent intent = new Intent(mContext, PlaySongActivity.class);
songlist = HomeFragment.arrayList;
songlist = new ArrayList<>();
// 2. Store the song information into the Intent object to be sent over to the destination screen.
intent.putExtra("id", song.getId());
intent.putExtra("title", song.getTitle());
intent.putExtra("artist", song.getArtist());
intent.putExtra("fileLink", song.getFileLink());
intent.putExtra("coverArt", song.getCoverArt());
intent.putExtra("songs", songs);
intent.putExtra("songlist", (Serializable) songlist);
// 3. Launch the destination screen/activity
mContext.startActivity(intent);
}
public void filter(String charText){
charText = charText.toLowerCase(Locale.getDefault());
songlist.clear();
if (charText.length()==0){
songlist.addAll(arrayList);
}
else {
for (Song song : arrayList){
if (song.getTitle().toLowerCase(Locale.getDefault())
.contains(charText) || song.getArtist().toLowerCase(Locale.getDefault())
.contains(charText)){
songlist.add(song);
}
}
}
notifyDataSetChanged();
}
package sg.edu.tp.musicstream;
import android.content.Intent;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.PopupMenu;
import android.widget.SearchView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager.widget.ViewPager;
import com.google.android.material.tabs.TabLayout;
import java.util.ArrayList;
import sg.edu.tp.musicstream.ui.main.SectionsPagerAdapter;
import sg.edu.tp.musicstream.util.AppUtil;
public class HomeActivity extends AppCompatActivity {
private SectionsPagerAdapter sectionsPagerAdapter;
private SongCollection songCollection = new SongCollection();
static Song[] playlistSongs = new Song[14];
static ArrayList<Song> playlist = new ArrayList<>();
private Fragment homeFragment;
private Fragment playlistsFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
homeFragment = new HomeFragment();
playlistsFragment = new PlaylistsFragment();
sectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
ViewPager viewPager = findViewById(R.id.view_pager);
setUpViewPager(viewPager);
TabLayout tabs = findViewById(R.id.tabs);
tabs.setupWithViewPager(viewPager);
}
private void setUpViewPager(ViewPager viewPager) {
SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
sectionsPagerAdapter.addFragment(homeFragment, "Recommended Songs");
sectionsPagerAdapter.addFragment(playlistsFragment, "Playlist");
viewPager.setAdapter(sectionsPagerAdapter);
}
public void addToPlaylist (View view) {
String songId = view.getContentDescription().toString();
Song song = songCollection.searchById(SongCollection.recommendedSongs, songId);
playlist.add(song);
AppUtil.popMessage(this, "Added " + song.getTitle() + " to playlist!");
playlistSongs[playlist.size()] = song;
sectionsPagerAdapter.removeFragment(playlistsFragment, "Playlist");
sectionsPagerAdapter.addFragment(new PlaylistsFragment(), "Playlist");
ViewPager viewPager = findViewById(R.id.view_pager);
setUpViewPager(viewPager);
TabLayout tabs = findViewById(R.id.tabs);
tabs.setupWithViewPager(viewPager);
}
public void removeAll(View view) {
playlist.clear();
PlaylistsFragment.songAdapter.notifyDataSetChanged();
}
}
package sg.edu.tp.musicstream;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.text.TextUtils;
import android.view.MenuItem;
import java.util.ArrayList;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.widget.SearchView;
import androidx.fragment.app.Fragment;
public class HomeFragment extends Fragment {
private PlaylistsAdapter playlistsAdapter;
private ListView listView;
static ArrayList<Song> arrayList = new ArrayList<>();
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_home, container,false);
for (int index =0; index<SongCollection.recommendedSongs.length; index++) {
arrayList.add(SongCollection.recommendedSongs[index]);
}
listView = view.findViewById(R.id.listView);
playlistsAdapter = new PlaylistsAdapter(getActivity(), arrayList, SongCollection.recommendedSongs);
listView.setAdapter(playlistsAdapter);
setHasOptionsMenu(true);
return view;
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.menu, menu);
MenuItem myActionMenuItem = menu.findItem(R.id.search);
SearchView searchView = (SearchView)myActionMenuItem.getActionView();
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String s) {
return false;
}
@Override
public boolean onQueryTextChange(String s) {
if (TextUtils.isEmpty(s)){
playlistsAdapter.filter("");
listView.clearTextFilter();
}
else {
playlistsAdapter.filter(s);
}
return true;
}
});
super.onCreateOptionsMenu(menu, inflater);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id==R.id.settings){
Intent intent = new Intent(getActivity(), LoginActivity.class);
startActivity(intent);
return true;
}
if (id==R.id.logOut){
Intent intent = new Intent(getActivity(), LoginActivity.class);
startActivity(intent);
return true;
}
return super.onOptionsItemSelected(item);
}
}
package sg.edu.tp.musicstream;
import java.util.List;
import java.util.Random;
public class SongCollection
{
static Song[] recommendedSongs = new Song[14];
private Song[] playlist1 = new Song[5];
private Song[] playlist2 = new Song[5];
public SongCollection()
{
//Recommended Songs
Song photograph = new Song("S1000", "Photograph", "Ed Sheeran","097c7b735ceb410943cbd507a6e1dfda272fd8a8?cid=null",4.32, R.drawable.photograph);
Song theWayYouLookTonight = new Song("S1001", "The Way You Look Tonight", "Michael Buble","a5b8972e764025020625bbf9c1c2bbb06e394a60?cid=null",4.39,R.drawable.michael_buble_collection);
Song billieJean = new Song("S1002", "Billie Jean", "Michael Jackson","f504e6b8e037771318656394f532dede4f9bcaea?cid=2afe87a64b0042dabf51f37318616965",4.39,R.drawable.billie_jean);
Song spark = new Song("S1003", "Spark", "TAEYEON","e857ae54599f2cca1703b598cef871664f36e72e?cid=2afe87a64b0042dabf51f37318616965", 3.63, R.drawable.spark);
Song darkside = new Song("S1004", "Darkside", "Alan Walker","2acc534ac733f8868c98e13e4f71917fae2e3ce3?cid=2afe87a64b0042dabf51f37318616965", 3.53, R.drawable.darkside);
Song diamondHeart = new Song("S1005", "Diamond Heart", "Alan Walker","d75c2b8e870acb087872bd49eeb5d6efb37cfc9d?cid=2afe87a64b0042dabf51f37318616965", 4.01, R.drawable.diamond_heart);
Song ocean= new Song("S1006", "Ocean (feat. Khalid)", "Martin Garrix","5ce5ed5600e96f1604aff6b05c0dc35319023a1c?cid=2afe87a64b0042dabf51f37318616965", 3.61, R.drawable.ocean);
Song numb = new Song("S1007", "Numb", "Linkin Park","e6ccf7717f8a167bfea4afc1bf7da1a0cd707fbb?cid=2afe87a64b0042dabf51f37318616965", 3.09, R.drawable.numb);
Song sadForever = new Song("S1008", "Sad Forever", "Lauv","1250fb3bea03aee6da908ea67420ddd954ad812a?cid=2afe87a64b0042dabf51f37318616965", 3.39, R.drawable.sad_forever);
Song kyokiranbu = new Song("S1009", "Kyokiranbu", "GARNiDELiA","ec373ab20f18e1a4a7b19b3abaac3ce605690abd?cid=2afe87a64b0042dabf51f37318616965", 4.32, R.drawable.kyokiranbu);
Song gokurakuJoudo= new Song("S1010", "Gokuraku Joudo", "GARNiDELiA","8924599ac778ebfbac7ddc2e5cc87961f82f736c?cid=2afe87a64b0042dabf51f37318616965", 3.65, R.drawable.gokuraku_joudo);
Song connect = new Song("S1011", "Connect", "ClariS","6692db454109aa077ed25e65df82a06d34017da6?cid=2afe87a64b0042dabf51f37318616965", 4.5, R.drawable.connect);
Song wannabe = new Song("S1012", "WANNABE", "ITZY", "2bae7f42bbae3cd75228d6400e37515b79467928?cid=2afe87a64b0042dabf51f37318616965", 3.19, R.drawable.wannabe);
Song icy = new Song("S1013", "ICY", "ITZY", "118a0dea24f229f51ffff23a9d334cf5714dbaf6?cid=2afe87a64b0042dabf51f37318616965", 3.19, R.drawable.icy);
recommendedSongs[0] = photograph;
recommendedSongs[1] = theWayYouLookTonight;
recommendedSongs[2] = billieJean;
recommendedSongs[3] = spark;
recommendedSongs[4] = darkside;
recommendedSongs[5] = diamondHeart;
recommendedSongs[6] = ocean;
recommendedSongs[7] = numb;
recommendedSongs[8] = sadForever;
recommendedSongs[9] = kyokiranbu;
recommendedSongs[10] = gokurakuJoudo;
recommendedSongs[11] = connect;
recommendedSongs[12] = wannabe;
recommendedSongs[13] = icy;
}
在您的适配器中，您有三种不同的方式来存储歌曲：
Song[] songs; List<Song> songlist; ArrayList<Song> arrayList;
这是一个问题。选择一种类型，并在任何地方使用它。
适配器正在围绕getCount()方法构建其逻辑：
@Override public int getCount() { return songlist.size(); }
使用songlist。但是您的onClick()方法使用songs:
@Override public void onClick(View v) { for (int index = 0; index < songs.length; index++) // ... }
如果将其更改为使用songlist，则问题可能会消失。