我是否正确地将光标与SQLite一起使用

Question

我第一次"试验"Android Studio和SQLite。我的应用屏幕在打开新活动时变为白色并冻结，该活动应显示我的 SQL 查询值。

public class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper (Context context) {
    super(context,"book.db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("create table books (ID INTEGER NOT NULL PRIMARY KEY, " +
            "BOOK_TITLE TEXT NOT NULL, BOOK_CATEGORY TEXT NOT NULL, " +
            "BOOK_DESCRIPTION TEXT NOT NULL)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("drop table if exists books");
    onCreate(db);
}
public boolean insertData(String book_title_, String book_category_, String book_description_)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues cValues = new ContentValues();
    cValues.put("BOOK_TITLE", book_title_);
    cValues.put("BOOK_CATEGORY", book_category_);
    cValues.put("BOOK_DESCRIPTION", book_description_);
    long result = db.insert("book", null, cValues);
    if (result == -1)
        return false;
    return true;
}
public Cursor getAllData()
{
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("SELECT * FROM book", null);
    return res;
}
}

我发现问题在于从另一个类调用 getAllData(( 函数。按照我的逻辑，一切都应该正常工作吗？我虽然问题出在我的查询中，但根据谷歌的说法，我已经做得很好。有什么建议吗？

Answer 1

试试这个方法。这是非常有效的方法：

public List<Movie> getAllData()
{
    List<Movie> movies_list = new ArrayList<>();
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("SELECT * FROM movie_collection", null);
    while(res.moveToNext())
    {
        movies_list.add(new Movie(res.getString(1)+"n", res.getString(2)+"n", res.getString(3)+"n", R.drawable.gladiator));
    }
    res.close();
    return movies_list;
}

和 viewAll(( 方法：

public void viewAll()
{
    movies_list = movie_database.getAllData();
    // do whatever you want
}