更新 ArrayList 适配器

Question

我觉得我咬的有点多，我不能咀嚼。我正在创建一个虚拟音乐播放器，我想添加一个按钮，用户可以将 Song() 对象添加到 ArrayList。问题是我在 onCreate() 方法中将 Song 对象添加到 Array 中。我有一个膨胀 PopUpView 的按钮，在该视图中我有另一个按钮，它从编辑字段中获取 getText() 并将一个项目添加到 ArrayList，当点击“完成”按钮时，PopUPView 被关闭并且新歌曲() 出现在歌曲列表中，但是当我返回主菜单然后返回歌曲列表时，用户添加的新对象不再存在。

public class AllSongsActivity<name> extends AppCompatActivity {

ArrayList<Song> songs = new ArrayList<Song>();

private AlertDialog.Builder dialogBuilder;
private AlertDialog dialog;
private EditText songNameEditText;
private EditText artistNameEditText;
private EditText genreNameEditText;
private CheckBox isFavoriteCheckBox;

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

    ListView listView = (ListView) findViewById(R.id.list);
    //Create List Of Song
    songs.add(new Song("Fever", "Dua Lipa", "POP", true));
    songs.add(new Song("Lonely", "Justin Bieber", "POP", false));
    songs.add(new Song("Courage To Change", "Sia", "POP", true));
    songs.add(new Song("Monster", "Shawn Mendes", "POP", false));
    songs.add(new Song("Dance Monkey", "Tones And I", "POP", true));
    songs.add(new Song("Masterpeice", "DaBaby", "RAP", false));
    songs.add(new Song("Wolves", "Big Sean", "RAP", false));
    songs.add(new Song("Trust", "Fivo Foreign", "RAP", false));
    songs.add(new Song("Back", "Jeezy", "RAP", false));
    songs.add(new Song("Bad Boy", "Juice Wrld", "RAP", true));
    songs.add(new Song("Deeper", "DubVision", "EDM", true));
    songs.add(new Song("Sick Of You", "Jerome", "EDM", true));
    songs.add(new Song("Paul Is Dead", "Scooter", "EDM", true));
    songs.add(new Song("All I Need", "Slushii", "EDM", true));
    songs.add(new Song("Willow", "Taylor Swift", "POP", false));

    ListAdapter songAdapter = new SongAdapter(this, songs);
    listView.setAdapter(songAdapter);

    Button addSongButton = (Button) findViewById(R.id.add_song_button);
    addSongButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            popUpWindow();
        }
    });
}


public void popUpWindow() {
    dialogBuilder = new AlertDialog.Builder(this);
    final View addNewSongView = getLayoutInflater().inflate(R.layout.add_song_popup_window, null);
    dialogBuilder.setView(addNewSongView);
    dialog = dialogBuilder.create();
    int sizeOfArray = songs.size();
    System.out.println("This is the size of the array before songs added" + sizeOfArray);
    dialog.show();

    Button addNewSongButton = (Button)dialog.findViewById(R.id.done_button);
    addNewSongButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            songNameEditText = (EditText)dialog.findViewById(R.id.song_name_edit_text);
            artistNameEditText = (EditText)dialog.findViewById(R.id.arist_name_edit_text);
            genreNameEditText = (EditText)dialog.findViewById(R.id.genre_edit_text);
            isFavoriteCheckBox = (CheckBox)dialog.findViewById(R.id.favorite_checkbox);
            int songsSize = songs.size();

            String songName = songNameEditText.getText().toString();
            String artistName = artistNameEditText.getText().toString();
            String genreName = genreNameEditText.getText().toString();
            Boolean isFavorite = isFavoriteCheckBox.isSelected();

            if (songName.matches("") || artistName.matches("") || genreName.matches("")) {
                Toast.makeText(AllSongsActivity.this, "Please Fillout All Fields",Toast.LENGTH_SHORT).show();
            }else {
                    Song newObject = new Song(songName, artistName, genreName, isFavorite);
                    songs.add(newObject);
                    dialog.dismiss();
            }
        }
    });
}

我已经学习了几个月的 Android 开发，所以我知道我的代码真的很乱，而且没有使用最好的技术。

Answer 1

代码中的问题：songs 列表是 AllSongsActivity 的一个属性。如果您关闭 AllSongsActivity - 来自活动和 歌曲 列表的所有数据都会消失！

保存新歌曲的简单但不正确的方法是使用 songs 的 static 修饰符： static ArrayList<Song> songs = new ArrayList<String>() {{ add(new Song("Fever", "Dua Lipa", "POP", true)); add(new Song("Lonely", "Justin Bieber", "POP", false)); }};

正确的方法——学习如何在数据库中存储数据：https://developer.android.com/training/data-storage/room