尝试更改数据库中的 DATABASE_VERSION 即当前为 7 后创建一个新表。
编辑
现在尝试以这种方式创建一个表：
public class DatabaseManager {
// the Activity or Application that is creating an object from this class.
Context context;
// a reference to the database used by this application/object
private SQLiteDatabase db;
// These constants are specific to the database. They should be
// changed to suit your needs.
private final String DB_NAME = "database_name_2";
private final int DB_VERSION = 8;
// These constants are specific to the database table. They should be
// changed to suit your needs.
private final String TABLE_NAME = "database_table";
private final String TABLE_ROW_ID = "id";
private final String TABLE_ROW_ONE = "table_row_one";
private final String TABLE_ROW_TWO = "table_row_two";
private final String TABLE_ROW_THREE = "table_row_three";
public DatabaseManager(Context context) {
this.context = context;
// create or open the database
CustomSQLiteOpenHelper helper = new CustomSQLiteOpenHelper(context);
this.db = helper.getWritableDatabase();
}
/**********************************************************************
* ADDING A ROW TO THE DATABASE TABLE
*
* This is an example of how to add a row to a database table using this
* class. You should edit this method to suit your needs.
*
* the key is automatically assigned by the database
*
* @param rowStringOne
* the value for the row's first column
* @param rowStringTwo
* the value for the row's second column
*/
public void addRow(String rowStringOne, String rowStringTwo, String qty) {
// this is a key value pair holder used by android's SQLite functions
ContentValues values = new ContentValues();
values.put(TABLE_ROW_ONE, rowStringOne);
values.put(TABLE_ROW_TWO, rowStringTwo);
values.put(TABLE_ROW_THREE, qty);
// ask the database object to insert the new data
try {
db.insert(TABLE_NAME, null, values);
} catch (Exception e) {
Log.e("DB ERROR", e.toString());
e.printStackTrace();
}
}
/**********************************************************************
* DELETING A ROW FROM THE DATABASE TABLE
*
* This is an example of how to delete a row from a database table using
* this class. In most cases, this method probably does not need to be
* rewritten.
*
* @param rowID
* the SQLite database identifier for the row to delete.
*/
public void deleteRow(long rowID) {
// ask the database manager to delete the row of given id
try {
db.delete(TABLE_NAME, TABLE_ROW_ID + "=" + rowID, null);
} catch (Exception e) {
Log.e("DB ERROR", e.toString());
e.printStackTrace();
}
}
/**********************************************************************
* UPDATING A ROW IN THE DATABASE TABLE
*
* This is an example of how to update a row in the database table using
* this class. You should edit this method to suit your needs.
*
* @param rowID
* the SQLite database identifier for the row to update.
* @param rowStringOne
* the new value for the row's first column
* @param rowStringTwo
* the new value for the row's second column
*/
public void updateRow(long rowID, String rowStringOne, String rowStringTwo,
String qty) {
// this is a key value pair holder used by android's SQLite functions
ContentValues values = new ContentValues();
values.put(TABLE_ROW_ONE, rowStringOne);
values.put(TABLE_ROW_TWO, rowStringTwo);
values.put(TABLE_ROW_THREE, qty);
// ask the database object to update the database row of given rowID
try {
db.update(TABLE_NAME, values, TABLE_ROW_ID + "=" + rowID, null);
} catch (Exception e) {
Log.e("DB Error", e.toString());
e.printStackTrace();
}
}
/**********************************************************************
* RETRIEVING A ROW FROM THE DATABASE TABLE
*
* This is an example of how to retrieve a row from a database table using
* this class. You should edit this method to suit your needs.
*
* @param rowID
* the id of the row to retrieve
* @return an array containing the data from the row
*/
public ArrayList<Object> getRowAsArray(long rowID) {
// create an array list to store data from the database row.
// I would recommend creating a JavaBean compliant object
// to store this data instead. That way you can ensure
// data types are correct.
ArrayList<Object> rowArray = new ArrayList<Object>();
Cursor cursor;
try {
// this is a database call that creates a "cursor" object.
// the cursor object store the information collected from the
// database and is used to iterate through the data.
cursor = db.query(TABLE_NAME, new String[] { TABLE_ROW_ID,
TABLE_ROW_ONE, TABLE_ROW_TWO, TABLE_ROW_THREE },
TABLE_ROW_ID + "=" + rowID, null, null, null, null, null);
// move the pointer to position zero in the cursor.
cursor.moveToFirst();
// if there is data available after the cursor's pointer, add
// it to the ArrayList that will be returned by the method.
if (!cursor.isAfterLast()) {
do {
rowArray.add(cursor.getLong(0));
rowArray.add(cursor.getString(1));
rowArray.add(cursor.getString(2));
rowArray.add(cursor.getString(3));
} while (cursor.moveToNext());
}
// let java know that you are through with the cursor.
cursor.close();
} catch (SQLException e) {
Log.e("DB ERROR", e.toString());
e.printStackTrace();
}
// return the ArrayList containing the given row from the database.
return rowArray;
}
/**********************************************************************
* RETRIEVING ALL ROWS FROM THE DATABASE TABLE
*
* This is an example of how to retrieve all data from a database table
* using this class. You should edit this method to suit your needs.
*
* the key is automatically assigned by the database
*/
public ArrayList<ArrayList<Object>> getAllRowsAsArrays() {
// create an ArrayList that will hold all of the data collected from
// the database.
ArrayList<ArrayList<Object>> dataArrays = new ArrayList<ArrayList<Object>>();
// this is a database call that creates a "cursor" object.
// the cursor object store the information collected from the
// database and is used to iterate through the data.
Cursor cursor;
try {
// ask the database object to create the cursor.
cursor = db.query(TABLE_NAME, new String[] { TABLE_ROW_ID,
TABLE_ROW_ONE, TABLE_ROW_TWO, TABLE_ROW_THREE }, null,
null, null, null, null);
// move the cursor's pointer to position zero.
cursor.moveToFirst();
// if there is data after the current cursor position, add it
// to the ArrayList.
if (!cursor.isAfterLast()) {
do {
ArrayList<Object> dataList = new ArrayList<Object>();
dataList.add(cursor.getLong(0));
dataList.add(cursor.getString(1));
dataList.add(cursor.getString(2));
dataList.add(cursor.getString(3));
dataArrays.add(dataList);
}
// move the cursor's pointer up one position.
while (cursor.moveToNext());
}
} catch (SQLException e) {
Log.e("DB Error", e.toString());
e.printStackTrace();
}
// return the ArrayList that holds the data collected from
// the database.
return dataArrays;
}
/**********************************************************************
* THIS IS THE BEGINNING OF THE INTERNAL SQLiteOpenHelper SUBCLASS.
*
* I MADE THIS CLASS INTERNAL SO I CAN COPY A SINGLE FILE TO NEW APPS AND
* MODIFYING IT - ACHIEVING DATABASE FUNCTIONALITY. ALSO, THIS WAY I DO NOT
* HAVE TO SHARE CONSTANTS BETWEEN TWO FILES AND CAN INSTEAD MAKE THEM
* PRIVATE AND/OR NON-STATIC. HOWEVER, I THINK THE INDUSTRY STANDARD IS TO
* KEEP THIS CLASS IN A SEPARATE FILE.
*********************************************************************/
/**
* This class is designed to check if there is a database that currently
* exists for the given program. If the database does not exist, it creates
* one. After the class ensures that the database exists, this class will
* open the database for use. Most of this functionality will be handled by
* the SQLiteOpenHelper parent class. The purpose of extending this class is
* to tell the class how to create (or update) the database.
*
* @author Randall Mitchell
*
*/
private class CustomSQLiteOpenHelper extends SQLiteOpenHelper {
public CustomSQLiteOpenHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// This string is used to create the database. It should
// be changed to suit your needs.
String newTableQueryString = "create table " + TABLE_NAME + " ("
+ TABLE_ROW_ID
+ " integer primary key autoincrement not null,"
+ TABLE_ROW_ONE + " text," + TABLE_ROW_TWO + " text"
+ TABLE_ROW_THREE + " text" + ");";
// execute the query string to the database.
db.execSQL(newTableQueryString);
String newTableQueryString2 = "alter table " + TABLE_NAME
+ " ADD COLUMN " + TABLE_ROW_THREE + " text";
// execute the query string to the database.
db.execSQL(newTableQueryString2);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// NOTHING TO DO HERE. THIS IS THE ORIGINAL DATABASE VERSION.
// OTHERWISE, YOU WOULD SPECIFIY HOW TO UPGRADE THE DATABASE.
}
}
}