我找到了一个在互联网上搜索android资源的数据库适配器。我目前正在尝试将位置等信息存储在数据库中。我得到了它的工作，但当我回去尝试添加更多列时，我得到的错误，如“列不存在”。所以我的问题是，如何删除数据库并使用这些新列重新创建它？这是我的代码，一切正常，直到我添加“戳”字符串......
// ------------------------------------ DBADapter.java ---------------------------------------------
// TODO: Change the package to match your project.
package biz.tanners.geo_x;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
// TO USE:
// Change the package (at top) to match your project.
// Search for "TODO", and make the appropriate changes.
public class DBAdapter {
/////////////////////////////////////////////////////////////////////
// Constants & Data
/////////////////////////////////////////////////////////////////////
// For logging:
private static final String TAG = "DBAdapter2";
// DB Fields
public static final String KEY_ROWID = "_id";
public static final int COL_ROWID = 0;
/*
* CHANGE 1:
*/
// TODO: Setup your fields here:
public static final String KEY_NAME = "name";
public static final String KEY_LONGITUDE = "longitude";
public static final String KEY_LATTITUDE = "lattitude";
public static final String KEY_STAMP = "stamp";
// TODO: Setup your field numbers here (0 = KEY_ROWID, 1=...)
public static final int COL_NAME = 1;
public static final int COL_LONGITUDE= 2;
public static final int COL_LATTITUDE = 3;
public static final int COL_STAMP = 4;
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_NAME, KEY_LONGITUDE, KEY_LATTITUDE, KEY_STAMP};
public static final String DATABASE_NAME = "MyDb";
public static final String DATABASE_TABLE = "mainTable";
public static final int DATABASE_VERSION = 4;
private static final String DATABASE_CREATE_SQL =
"create table " + DATABASE_TABLE
+ " (" + KEY_ROWID + " integer primary key autoincrement, "
/*
* CHANGE 2:
*/
// TODO: Place your fields here!
// + KEY_{...} + " {type} not null"
// - Key is the column name you created above.
// - {type} is one of: text, integer, real, blob
// (http://www.sqlite.org/datatype3.html)
// - "not null" means it is a required field (must be given a value).
// NOTE: All must be comma separated (end of line!) Last one must have NO comma!!
+ KEY_NAME + " text not null, "
+ KEY_LONGITUDE + " double not null, "
+ KEY_LATTITUDE + " double not null, " + KEY_STAMP + " text not null"
// Rest of creation:
+ ");";
// Context of application who uses us.
private final Context context;
private DatabaseHelper myDBHelper;
private SQLiteDatabase db;
/////////////////////////////////////////////////////////////////////
// Public methods:
/////////////////////////////////////////////////////////////////////
public DBAdapter(Context ctx) {
this.context = ctx;
myDBHelper = new DatabaseHelper(context);
}
// Open the database connection.
public DBAdapter open() {
db = myDBHelper.getWritableDatabase();
return this;
}
// Close the database connection.
public void close() {
myDBHelper.close();
}
// Add a new set of values to the database.
public long insertRow(String name, double longitude, double lattitude, String stamp) {
/*
* CHANGE 3:
*/
// TODO: Update data in the row with new fields.
// TODO: Also change the function's arguments to be what you need!
// Create row's data:
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_LONGITUDE, longitude);
initialValues.put(KEY_LATTITUDE, lattitude);
initialValues.put(KEY_STAMP, stamp);
// Insert it into the database.
return db.insert(DATABASE_TABLE, null, initialValues);
}
// Delete a row from the database, by rowId (primary key)
public boolean deleteRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
return db.delete(DATABASE_TABLE, where, null) != 0;
}
public void deleteAll() {
Cursor c = getAllRows();
long rowId = c.getColumnIndexOrThrow(KEY_ROWID);
if (c.moveToFirst()) {
do {
deleteRow(c.getLong((int) rowId));
} while (c.moveToNext());
}
c.close();
}
// Return all data in the database.
public Cursor getAllRows() {
String where = null;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Get a specific row (by rowId)
public Cursor getRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Change an existing row to be equal to new data.
public boolean updateRow(long rowId, String name, double longitude, double lattitude, String stamp) {
String where = KEY_ROWID + "=" + rowId;
/*
* CHANGE 4:
*/
// TODO: Update data in the row with new fields.
// TODO: Also change the function's arguments to be what you need!
// Create row's data:
ContentValues newValues = new ContentValues();
newValues.put(KEY_NAME, name);
newValues.put(KEY_LONGITUDE, longitude);
newValues.put(KEY_LATTITUDE, lattitude);
newValues.put(KEY_STAMP, stamp);
// Insert it into the database.
return db.update(DATABASE_TABLE, newValues, where, null) != 0;
}
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_SQL);
}
@Override
public void onUpgrade(SQLiteDatabase _db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading application's database from version " + oldVersion
+ " to " + newVersion + ", which will destroy all old data!");
// Destroy old database:
_db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
// Recreate new database:
onCreate(_db);
}
}
}
Error Code : 1 (SQLITE_ERROR)
Caused By : SQL(query) error or missing database.
(no such column: stamp (code 1): , while compiling: SELECT DISTINCT _id, name, longitude, lattitude, stamp FROM mainTable2)
答案 0 :(得分：1)
按照我的理解给你答案。您可以进行删除表查询，并在需要删除该表时调用它，并且只要您想创建该表，就可以进行创建表查询。