按字母顺序排序音乐播放器的播放列表（Android Studio）

Question

我下载了这个项目：

https://projectworlds.in/android-projects-with-source-code/android-music-player-project-with-source-code/

我会按字母顺序对“所有歌曲”部分中的歌曲进行排序。我试图把它放在 onCreate 中：

Collections.sort(songList, Comparator.comparing((Function<? super Object, ? extends Comparable>) songList));

在此处查看代码：

public class MainActivity extends AppCompatActivity implements View.OnClickListener, AllSongFragment.createDataParse, FavSongFragment.createDataParsed, CurrentSongFragment.createDataParsed {

    private Menu menu;

    private ImageButton imgBtnPlayPause, imgbtnReplay, imgBtnPrev, imgBtnNext, imgBtnSetting;
    private TabLayout tabLayout;
    private ViewPager viewPager;
    private SeekBar seekbarController;
    private DrawerLayout mDrawerLayout;
    private TextView tvCurrentTime, tvTotalTime;


    private ArrayList<SongsList> songList;
    private int currentPosition;
    private String searchText = "";
    private SongsList currSong;

    private boolean checkFlag = false, repeatFlag = false, playContinueFlag = false, favFlag = true, playlistFlag = false;
    private final int MY_PERMISSION_REQUEST = 100;
    private int allSongLength;
    MediaPlayer mediaPlayer;
    Handler handler;
    Runnable runnable;

    @RequiresApi(api = Build.VERSION_CODES.N)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
        grantedPermission();
        onPrepared();
        //Sorting playlist here
        Collections.sort(songList, Comparator.comparing((Function<? super Object, ? extends Comparable>) songList));

    }

但应用程序崩溃了。 arraylist 没有对象，所以我不能使用 toCompare（例如：obj 1 和 obj 2）。我想比较 ArrayList 本身>

对此有什么想法吗？提前致谢。

SongList.java：

package com.example.soc_macmini_15.musicplayer.Model;
public class SongsList {

    private String title;
    private String subTitle;
    private String path;

    public String getPath() {
        return path;
    }

    public void setPath(String path) {
        this.path = path;
    }

    public SongsList(String title, String subTitle, String path) {
        this.title = title;
        this.subTitle = subTitle;
        this.path = path;

    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getSubTitle() {
        return subTitle;
    }

}

Answer 1

Comparator.comparing 中的 Function 应作为方法参考提供：

Collections.sort(songList, Comparator.comparing(SongList::getTitle));