似乎由于未知原因，SQLite表已停止填充

Question

该应用程序运行良好，但是方法Cursor.moveToFirst()开始返回false，并且该应用程序的列表已不再出现在Fragment中。

我认为这是在我将constat的名称从IMAGE_URI更改为IMAGE_URL，并将imageUri更改为imageUrl之后开始的。不确定。

我尝试调试和搜索类似的情况，但是原因很多。调试时，我无法进入onCreate类的SQLiteHelper来找出表填充期间发生的情况（似乎该表存在，因为该表的空db正在创建），所以我无法调试也无法搜索类似的问题，因为在Logcat中找不到相关的输出。

GetDatabase

该类用于与SQLiteOpenHelper类进行某些通信。

public class GetDatabase {

    private static final int DB_VERSION = 1; //required for the constructor
    public static final String dbName = "moviesList";

    private SQLiteOpenHelper sqLiteOpenHelper;
    private SQLiteDatabase db ;

    public GetDatabase(Context context) {
        Log.d("GetDatabase", "Cont.");

        this.sqLiteOpenHelper = new SQLiteHelper(context, dbName, null, DB_VERSION);
    }

    public void open() {
       db = sqLiteOpenHelper.getWritableDatabase();
    }

    public void close() {
        if (sqLiteOpenHelper != null) {
            sqLiteOpenHelper.close();
        }
    }

    public ArrayList<Movie> getMovies() {
        String[] columns = {
                Movie.ID,
                Movie.TITLE,
                Movie.IMAGE_URL,
                Movie.RATING,
                Movie.RELEASE_YEAR,
                Movie.GENRE
        };

        // sorting orders
        String sortOrder =
                Movie.RELEASE_YEAR + " ASC";
        ArrayList<Movie> moviesList = new ArrayList<>();

        Cursor cursor = db.query(TABLE_NAME, //Table to query
                columns,
                null,
                null,
                null,
                null,
                sortOrder);

        if (cursor.moveToFirst()) {
            do {
                Movie movie = new Movie();
                movie.setMovieId(Integer.parseInt(cursor.getString(cursor.getColumnIndex(Movie.ID))));
                movie.setTitle(cursor.getString(cursor.getColumnIndex(Movie.TITLE)));
                movie.setImageUrl(cursor.getString(cursor.getColumnIndex(Movie.IMAGE_URL)));
                movie.setRating(cursor.getDouble(cursor.getColumnIndex(Movie.RATING)));
                movie.setReleaseYear(cursor.getInt(cursor.getColumnIndex(Movie.RELEASE_YEAR)));
                movie.setGenre(cursor.getString(cursor.getColumnIndex(Movie.GENRE)));
                // Adding a movie to the list
                moviesList.add(movie);
            } while (cursor.moveToNext());
        }
        Log.d(TAG, "The movies list from sqlite: " + moviesList);
        cursor.close();
        db.close();

        return moviesList;
    }

    private Cursor getData(int id) {
        return db.rawQuery( "select * from " + TABLE_NAME + " where id="+id+"", null );
    }

    public Cursor getMovieDetails(int movieId) {// For viewing details of a specific item

        Cursor cursor = getData(movieId);
        cursor.moveToFirst();

        return cursor;
    }
}

SQliteHelper

SQLiteOpenHelper类

public class SQLiteHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "movies.db";
    private static final int DB_VERSION = 1; //required for the constructor
    private static final String TABLE_NAME = "movies";

    private String fileName = "movies.json";
    private String appName = "MoviesList";
    private String path = getExternalStorageDirectory() + "/" + appName + "/" + fileName;

    private String jsonString = null;

    private SQLiteDatabase db;

    // The cont. for saving to SQLite .Called from SplashActivity after downloading the JSON
    public SQLiteHelper(Context context, String dbName, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        Log.d(TAG, "At SQLiteHelper");

        createSQLIteTable(db);
        if(tableIsEmpty(db)) {
            try {
                parseJsonAndInsertToSQLIte(db);
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }

    private void createSQLIteTable(SQLiteDatabase db) {

        //creating a table for SQLite
        String CREATE_SQL_TABLE_STRING = "CREATE TABLE IF NOT EXISTS "+TABLE_NAME
                + " ("
                + Movie.ID + " INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL ,"
                + Movie.TITLE + " TEXT,"
                + Movie.IMAGE_URL + " TEXT,"
                + Movie.RATING + " TEXT,"
                + Movie.RELEASE_YEAR + " TEXT,"
                + Movie.GENRE + " TEXT "
                + ")";

        Log.i(TAG,"created sql table: "+CREATE_SQL_TABLE_STRING);

        db.execSQL(CREATE_SQL_TABLE_STRING);
    }

    private void parseJsonAndInsertToSQLIte(SQLiteDatabase db) throws JSONException {
        // parsing the json
        String jsonString = getJsonFileData();
        JSONArray moviesArray = new JSONArray(jsonString);
        ContentValues insertValues;

        for (int i = 0; i < moviesArray.length(); i++) {

            JSONObject jsonObject = moviesArray.getJSONObject(i);

            String title = jsonObject.getString("title");
            String imageUrl = jsonObject.getString("imageUrl");
            String rating = jsonObject.getString("rating");
            String releaseYear = jsonObject.getString("releaseYear");
            String genre = jsonObject.getString("genre");

            insertValues = new ContentValues();

            insertValues.put(Movie.TITLE, title);
            insertValues.put(Movie.IMAGE_URL, imageUrl);
            insertValues.put(Movie.RATING, rating);
            insertValues.put(Movie.RELEASE_YEAR, releaseYear);
            insertValues.put(Movie.GENRE, genre);
            long res = db.insert(TABLE_NAME, null, insertValues);

            Log.i(TAG, "parsed and inserted to sql - row: " + res);
        }
    }

    private String getJsonFileData() {
        //loading the jsonString
        try {
            InputStream in = new FileInputStream(new File(path));
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));
            StringBuilder output = new StringBuilder();
            while ((jsonString = reader.readLine()) != null) {
                output.append(jsonString);
            }
            System.out.println(output.toString());   //Prints the string content read from input stream

            jsonString = output.toString();
            Log.d(TAG, "the jsonString was loaded");
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        return jsonString;
    }
}

如果我不能解决这个问题，我认为整个应用程序一文不值，因为我不知道需要纠正什么错误。

谢谢！

Answer 1

清除设置中的应用程序数据，然后再次运行您的应用程序。由于您在数据库列中进行了更改，因此除非您清除数据，否则它不会反映出来。

或

对数据库版本进行正确处理。每次更改数据库结构时，请使用onUpgrade方法删除所有表并增加数据库版本。

编辑：“清除数据”窗口