Sqlite CRUD-4个类中的操作扩展Asynctask？

Question

我想在后台任务中执行所有sqlite操作:插入、删除、更新和查询。

我必须为每个操作创建一个扩展AsyncTask的类吗？

我的意思是，最后我有4个类来处理这4个操作？

谢谢。

Answer 1

你有没有试过谷歌的房间库，它是一个包装器，并异步工作？

以下是文档和指南：https://developer.android.com/topic/libraries/architecture/room.html

Answer 2

房间是一个很好的解决方案。但是如果你想写一些手工代码，你可以这样做：

implementations

• Create泛型任务和

1. 创建泛型DAO扩展了AsyncTask。例如：

public interface GeneralDAO<O, I> extends Serializable {
    default O findById(long k) {
        SQLiteDatabase db = DatabaseManager.getInstance().openDatabase();

        Cursor cursor = db.query(getTableName(), null, getColumnId() + " = ?",
                new String[]{String.valueOf(k)}, null, null, null, null);
        if (cursor != null) {
            cursor.moveToFirst();
        }
        O t = map(cursor);
        cursor.close();
        Log.i(getTag(), "findById " + k + ": " + t);
        DatabaseManager.getInstance().closeDatabase();
        return t;
    }

    default List<O> getAll() {
        List<O> lst = new ArrayList<>();
        Log.i(getTag(), "getAll ... ");
        String selectQuery = "SELECT  * FROM " + getTableName();
        SQLiteDatabase db = DatabaseManager.getInstance().openDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        if (cursor != null && cursor.moveToFirst()) {
            do {
                O t = map(cursor);
                if (t != null) {
                    lst.add(t);
                }
            } while (cursor.moveToNext());
        }
        cursor.close();
        DatabaseManager.getInstance().closeDatabase();
        return lst;
    }

}

public class BankerDAO implements GeneralDAO<Banker, Banker> {
    ...
}

public class CreateTask<O, I> extends AsyncTask<I, Void, Long> {

    protected GeneralDAO<O, I> dao;
    protected ProgressBar progressBar;

    public CreateTask(ProgressBar progressBar, GeneralDAO<O, I> dao) {
        this.progressBar = progressBar;
        this.dao = dao;
    }

    @Override
    protected Long doInBackground(I... ins) {
        return dao.add(ins[0]);
    }
}

public class GetAllTask<O, I> extends AsyncTask<I, Void, List<O>> {

    protected GeneralDAO<O, I> dao;
    protected ProgressBar progressBar;

    public GetAllTask(ProgressBar progressBar, GeneralDAO<O, I> dao) {
        this.progressBar = progressBar;
        this.dao = dao;
    }

    @Override
    protected List<O> doInBackground(I... ins) {
        return dao.getAll();
    }
}

然后使用它们：

public class BankerViewModel extends ViewModel {
    private static final String TAG = "BankerViewModel";
    private BankerDAO bankerDAO;
    private MutableLiveData<List<Banker>> bankers;

    public BankerViewModel() {
        bankers = new MutableLiveData<>();
        bankerDAO = DAOFactory.getBankerDAO();
        try {
            bankers.setValue(new GetAllTask<Banker, Banker>(null, bankerDAO).execute().get());
        } catch (Exception e) {
            Log.e(TAG, e.getMessage(), e);
        }
    }

    public void addBanker(Banker banker) {
        try {
            Banker newBanker = new CreateAndGetTask<Banker, Banker>(null, bankerDAO).execute(banker).get();
            System.out.println("addBanker addAndGetNewInstance:" + newBanker.info());
            if (newBanker != null) {
                bankers.getValue().add(banker);
            }
        } catch (Exception e) {
            Log.e(TAG, e.getMessage(), e);
        }
    }
}

使用此解决方案，您仍然可以为CRUD任务创建4个类，但它们是泛型任务，您可以将它们用于其他实体