在数据库中添加第二个表
这是我的第一篇文章！ 我希望你能帮助我！ 🙂
我使用了开发人员doc中的NotePadExample提供的代码来创建数据库。 现在我想添加第二个表来存储不同的数据。 我可以毫无问题地添加注释，并且注释表的创建方式与我的路由表类似。 我只是“复制”并编辑了给定的代码，但是当我尝试插入新表时，我得到一个错误说：
“0ERROR / Database（370）：android.database.sqlite.SQLiteException：没有这样的表：routes :,同时编译：INSERT INTO路由（行，到达，持续时间，开始）VALUES（？，？，？，？）;”
有人可以快速查看我的DbAdapter类，尤其是onCreate（）方法。 并给我一个提示或解决方案？ 我真的没有看到任何问题。 我的代码编译没有任何错误..
码：
public class DbAdapter { public static final String KEY_FROM = "title"; public static final String KEY_TO = "body"; public static final String KEY_ROWID = "_id"; public static final String KEY_START = "start"; public static final String KEY_ARRIVAL = "arrival"; public static final String KEY_LINE = "line"; public static final String KEY_DURATION = "duration"; private static final String DATABASE_NAME = "data"; private static final String DATABASE_NOTESTABLE = "notes"; private static final String DATABASE_ROUTESTABLE = "routes"; private static final String TAG = "DbAdapter"; private DatabaseHelper mDbHelper; private SQLiteDatabase mDb; /** * Database creation sql statement */ private static final String DATABASE_CREATE_NOTES = "create table notes (_id integer primary key autoincrement, " + "title text not null, body text not null)"; private static final String DATABASE_CREATE_ROUTES = "create table routes (_id integer primary key autoincrement, " + "start , arrival , " + "line , duration );"; private static final int DATABASE_VERSION = 3; private final Context mCtx; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DATABASE_CREATE_NOTES); Log.d(TAG, "created notes table"); db.execSQL(DATABASE_CREATE_ROUTES); Log.d(TAG, "created routes table"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); db.execSQL("DROP TABLE IF EXISTS routes"); onCreate(db); } } /** * Constructor - takes the context to allow the database to be * opened/created * * @param ctx the Context within which to work */ public DbAdapter(Context ctx) { this.mCtx = ctx; } /** * Open the notes database. If it cannot be opened, try to create a new * instance of the database. If it cannot be created, throw an exception to * signal the failure * * @return this (self reference, allowing this to be chained in an * initialization call) * @throws SQLException if the database could be neither opened or created */ public DbAdapter open() throws SQLException { mDbHelper = new DatabaseHelper(mCtx); mDb = mDbHelper.getWritableDatabase(); return this; } public void close() { mDbHelper.close(); } /** * Create a new note using the title and body provided. If the note is * successfully created return the new rowId for that note, otherwise return * a -1 to indicate failure. * * @param title the title of the note * @param body the body of the note * @return rowId or -1 if failed */ public long createNote(String title, String body) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_FROM, title); initialValues.put(KEY_TO, body); return mDb.insert(DATABASE_NOTESTABLE, null, initialValues); } /** * Create a new route using the title and body provided. If the route is * successfully created return the new rowId for that route, otherwise return * a -1 to indicate failure. * * @param start the start time of the route * @param arrival the arrival time of the route * @param line the line number of the route * @param duration the routes duration * @return rowId or -1 if failed */ public long createRoute(String start, String arrival, String line, String duration){ ContentValues initialValues = new ContentValues(); initialValues.put(KEY_START, start); initialValues.put(KEY_ARRIVAL, arrival); initialValues.put(KEY_LINE, line); initialValues.put(KEY_DURATION, duration); return mDb.insert(DATABASE_ROUTESTABLE, null, initialValues); } /** * Delete the note with the given rowId * * @param rowId id of note to delete * @return true if deleted, false otherwise */ public boolean deleteNote(long rowId) { return mDb.delete(DATABASE_NOTESTABLE, KEY_ROWID + "=" + rowId, null) > 0; } /** * Return a Cursor over the list of all notes in the database * * @return Cursor over all notes */ public Cursor fetchAllNotes() { return mDb.query(DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, null, null, null, null, null); } /** * Return a Cursor over the list of all routes in the database * * @return Cursor over all routes */ public Cursor fetchAllRoutes() { return mDb.query(DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, null, null, null, null, null); } /** * Return a Cursor positioned at the note that matches the given rowId * * @param rowId id of note to retrieve * @return Cursor positioned to matching note, if found * @throws SQLException if note could not be found/retrieved */ public Cursor fetchNote(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Return a Cursor positioned at the route that matches the given rowId * * @param rowId id of route to retrieve * @return Cursor positioned to matching route * @throws SQLException if note could not be found/retrieved */ public Cursor fetchRoute(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Update the note using the details provided. The note to be updated is * specified using the rowId, and it is altered to use the title and body * values passed in * * @param rowId id of note to update * @param title value to set note title to * @param body value to set note body to * @return true if the note was successfully updated, false otherwise */ public boolean updateNote(long rowId, String title, String body) { ContentValues args = new ContentValues(); args.put(KEY_FROM, title); args.put(KEY_TO, body); return mDb.update(DATABASE_NOTESTABLE, args, KEY_ROWID + "=" + rowId, null) > 0; } public void deleteRoutesTable(SQLiteDatabase db){ db.delete("routes", null, null); } } 加
我想实现一个类似的方法
public void deleteTableRoutes(SQLiteDataBase db){ db.delete("routes", null, null); }
我的问题：我想从我没有引用我的数据库（据我所知）调用此函数作为我的deleteTableRoutes（SQLiteDataBase）的参数传递…
我认为您需要选择一个新的（更高版本）版本号，并修改onUpgrade方法以删除路由（如果存在）。 当然，您实际上可能不需要删除现有表（例如，创建和更改可能就足够了），但这样做与您当前的实现一致。
您将使用新版本调用SQLiteOpenHelper构造函数，它将在内部调用onUpgrade，传递旧版本和新版本。
代替：
@Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); onCreate(db); }
我不得不修改方法如下：
@Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); db.execSQL("DROP TABLE IF EXISTS routes"); // line added onCreate(db); }
我而不是：
private static final int DATABASE_VERSION = 2;
我改成了：
private static final int DATABASE_VERSION = 3;
但是，我并没有完全意识到对数据库版本的更改有真正的影响。