Android-Room(二)

前編に基づいてコードを最適化します.前のデータの操作はメインスレッドに置かれています.ここでは、データベースの操作に非同期タスクを導入します.
まず(Word)bean類で、変化はありません:

@Entity
public class Word {

    @PrimaryKey(autoGenerate = true)//     。        
    private int id;

    @ColumnInfo(name="english_word")//        
    private String word;

    @ColumnInfo(name="chinese_meaning")
    private String chineseMeaning;


    public Word(String word, String chineseMeaning) {
        this.word = word;
        this.chineseMeaning = chineseMeaning;
    }


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getWord() {
        return word;
    }

    public void setWord(String word) {
        this.word = word;
    }

    public String getChineseMeaning() {
        return chineseMeaning;
    }

    public void setChineseMeaning(String chineseMeaning) {
        this.chineseMeaning = chineseMeaning;
    }
}

Daoインタフェースは,呼び出すたびにビューを設定する必要がないようにLiveDataを導入した.

@Dao    //Database access object
public interface WordDao {

    @Insert
    void insertWords(Word...words);

    @Update
    void updateWords(Word... words);

    @Delete
    void deleteWords(Word... words);

    @Query("Delete From WORD")
    void deleteAllWords();

    @Query("Select * From Word order by id desc")
    LiveData<List<Word>> getAllWordsLive();
}

WordDatabaseは、セキュリティ上の問題のために、このオブジェクトを単一の例として書きます.

//singleton
@Database(entities = {Word.class},version = 1,exportSchema = false)
public abstract class WordDatabase extends RoomDatabase {

    private static WordDatabase INSTANCE;

    public synchronized static WordDatabase getDatabase(Context context){
        if(INSTANCE==null){
            INSTANCE= Room.databaseBuilder(context.getApplicationContext(),WordDatabase.class,"word database")
                    .build();
        }
        return INSTANCE;
    }

    public abstract WordDao getWordDao();
}

ViewModel:

public class MyViewModel extends AndroidViewModel {

    private WordRepository repository;


    public MyViewModel(@NonNull Application application) {
        super(application);
        repository=new WordRepository(getApplication());

    }

    public LiveData<List<Word>> getAllWordLive() {
        return repository.getAllWordLive();
    }

    void insertWords(Word... words){
        repository.insertWords(words);
    }

    void updataWords(Word... words){
        repository.updataWords(words);
    }
    void deleteWords(Word... words){
        repository.deleteWords(words);
    }
    void DeleteAllWords(){
        repository.DeleteAllWords();
    }
}

WordRepository、データベースの操作から分離されたクラス:

public class WordRepository {

    private WordDao wordDao;

    private LiveData<List<Word>> allWordLive;

    public WordRepository(Context context) {
        WordDatabase wordDatabase=WordDatabase.getDatabase(context.getApplicationContext());
        wordDao=wordDatabase.getWordDao();
        allWordLive=wordDao.getAllWordsLive();
    }

    public LiveData<List<Word>> getAllWordLive() {
        return allWordLive;
    }


    void insertWords(Word... words){
        new InsertAsyncTask(wordDao).execute(words);
    }

    void updataWords(Word... words){
        new UpdataAsyncTask(wordDao).execute(words);
    }
    void deleteWords(Word... words){
        new DeleteAsyncTask(wordDao).execute(words);
    }
    void DeleteAllWords(Word... words){
        new DeleteAllAsyncTask(wordDao).execute();
    }


    public static class InsertAsyncTask extends AsyncTask<Word,Void,Void>{

        private WordDao wordDao;

        public InsertAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }
        @Override
        protected Void doInBackground(Word... words) {
            wordDao.insertWords(words);
            return null;
        }
    }

    public static class UpdataAsyncTask extends AsyncTask<Word,Void,Void>{

        private WordDao wordDao;

        public UpdataAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }
        @Override
        protected Void doInBackground(Word... words) {
            wordDao.updateWords(words);
            return null;
        }
    }

    public static class DeleteAsyncTask extends AsyncTask<Word,Void,Void> {

        private WordDao wordDao;

        public DeleteAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }
        @Override
        protected Void doInBackground(Word... words) {
            wordDao.deleteWords(words);
            return null;
        }
    }

    public static class DeleteAllAsyncTask extends AsyncTask<Void,Void,Void>{

        private WordDao wordDao;

        public DeleteAllAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }
        @Override
        protected Void doInBackground(Void... voids) {
            wordDao.deleteAllWords();
            return null;
        }
    }
}

java:

    private MyViewModel viewModel;

    private TextView textView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_room_basic);
        textView=findViewById(R.id.tv_main);


        viewModel=new ViewModelProvider(this).get(MyViewModel.class);


        viewModel.getAllWordLive().observe(this, new Observer<List<Word>>() {
            @Override
            public void onChanged(List<Word> words) {
                StringBuilder text= new StringBuilder();
                for(int i=0;i<words.size();i++){
                    Word word=words.get(i);
                    text.append(word.getId()).append(":").append(word.getWord()).append("+").append(word.getChineseMeaning()).append("
");
                }
                textView.setText(text.toString());
            }
        });

    }

    public void insert(View view){
        Word word=new Word("Hello","  ");
        Word word1=new Word("World", "  ");
        viewModel.insertWords(word,word1);
    }

    public void update(View view) {
        Word word = new Word("Hi", " ");
        word.setId(228);
        viewModel.updataWords(word);
    }

    public void delete(View view){
        Word word=new Word("Hi", " ");
        word.setId(227);
        viewModel.deleteWords(word);
    }
    public void clear(View view){
        viewModel.DeleteAllWords();
    }