在数据库中增加一个第二表 [英] Adding a second table in a database

问题描述

这是我的第一篇文章！我希望你能帮助我！ ： - ）

This is my first post! I hope you can help me out! :-)

我用从开发文档所提供的NotePadExample的code创建一个数据库。现在我想添加第二个表来存储不同的数据。我没有问题，可以添加注释和笔记表以类似的方式创建为我的路由表。我简单的复制和编辑特定的code，但是当我尝试插入到新表中，我得到一个错误说：

I used the code provided by the NotePadExample from the developers doc to create a database. Now I want to add a second table to store different data. I can add notes without a problem, and the notes table is created in a similar way as my routes table is. I simply "copied" and edited the given code, but when I try to insert into the new table I get an error saying:

0ERROR /数据库（370）：android.database.sqlite.SQLiteException：没有这样的表：航线：在编制：？？INSERT INTO线路（线路，到达，持续时间，开始）VALUES（？，？ ）;

"0ERROR/Database(370): android.database.sqlite.SQLiteException: no such table: routes: , while compiling: INSERT INTO routes(line, arrival, duration, start) VALUES(?, ?, ?, ?);"

有人可以请大家快看我的DbAdapter类，尤其是的onCreate（）方法。并给我一个提示或解决方案？我实在看不出有什么问题。我的code编译没有任何错误。

Can someone please take quick look at my DbAdapter class, especially the onCreate() method. and give me a hint or a solution? I really don't see any problem. my code compiles without any errors..

在此先感谢！

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);
}

}

我想实现像

public void deleteTableRoutes(SQLiteDataBase db){
 db.delete("routes", null, null);
}

我的问题：我想从一个地步，我没有提到我的分贝（据我所知）调用这个函数来传递作为我deleteTableRoutes一个参数（SQLiteDataBase）...

my problem: I want to call this function from a point where I have no reference to my db (as far as I know) to pass as an argument for my deleteTableRoutes(SQLiteDataBase) ...

推荐答案

相反的：

@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);
    }

我不得不修改类似下面的方法：

I had to modify the method like the following:

@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);
    }

而不是我和：

And I instead of:

private static final int DATABASE_VERSION = 2;

我把它改为：

I changed it to:

private static final int DATABASE_VERSION = 3;

不过，我并不完全了解真正的影响更改数据库的版本了。

However, I'm not completely aware of the REAL affect the change to the database version had.

这篇关于在数据库中增加一个第二表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！