我在关于在一个数据库中存储多个表时遵循此示例Multiple Table SQLite DB Adapter(s) in Android?。
我创建了4个DBAdapter（DBAdapter，CarsDBAdapter，BoatsDBAdapter和CyclesDBAdapter）。但是在DBAdapter中，我在db适配器中创建了3个表。然后我为其他3 db适配器创建了3个非DBadaper类。这些表没有插入到数据库中，而且我不确定我应该在非dbadapter类中声明哪个DBAdapter。
我需要帮助。我将不胜感激任何帮助。
以下是我输入的代码。
DBAdapter.java
public class DBAdapter
{
public static final String DATABASE_NAME = "stuffIOwn";
public static final int DATABASE_VERSION = 2;
private static final String CREATE_TABLE_CARS = "create table cars(_id integer primary key autoincrement, " //$NON-NLS-1$
+CarsDBAdapter.NAME+ " TEXT," //$NON-NLS-1$
+CarsDBAdapter.MODEL+ " TEXT," //$NON-NLS-1$
+CarsDBAdapter.YEAR+ " TEXT" +");"; //$NON-NLS-1$
private static final String CREATE_TABLE_BOATS = "create table boats(_id integer primary key autoincrement, " //$NON-NLS-1$
+BoatsDBAdapter.NAME+ " TEXT," //$NON-NLS-1$
+BoatsDBAdapter.MODEL+ " TEXT," //$NON-NLS-1$
+BoatsDBAdapter.YEAR+ " TEXT" +");"; //$NON-NLS-1$
private static final String CREATE_TABLE_CYCLES = "create table cycles(_id integer primary key autoincrement, " //$NON-NLS-1$
+CyclesDBAdapter.NAME+ " TEXT," //$NON-NLS-1$
+CyclesDBAdapter.MODEL+ " TEXT," //$NON-NLS-1$
+CyclesDBAdapter.YEAR+ " TEXT" +");"; //$NON-NLS-1$
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
this.DBHelper = new DatabaseHelper(this.context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(CREATE_TABLE_CARS);
db.execSQL(CREATE_TABLE_BOATS);
db.execSQL(CREATE_TABLE_CYCLES);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
// Adding any table mods to this guy here
}
}//end DatabaseHelper class
public DBAdapter open() throws SQLException
{
this.db = this.DBHelper.getWritableDatabase();
return this;
}
/**
* close the db
*return type: void
*/
public void close()
{
this.DBHelper.close();
}
}
CarsDBAdapter.java
public class CarsDBAdapter
{
public static final String ROW_ID = "_id";
public static final String NAME = "name";
public static final String MODEL = "model";
public static final String YEAR = "year";
private static final String DATABASE_TABLE = "cars";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
private final Context mCtx;
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DBAdapter.DATABASE_NAME, null, DBAdapter.DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
}
}// end DatabaseHelper class
public CarsDBAdapter(Context ctx)
{
this.mCtx = ctx;
}
public CarsDBAdapter open() throws SQLException
{
this.mDbHelper = new DatabaseHelper(this.mCtx);
this.mDb = this.mDbHelper.getWritableDatabase();
return this;
}
public void close()
{
this.mDbHelper.close();
}
public long insertCars(String name, String model, String year)
{
ContentValues initialValues = new ContentValues();
initialValues.put(NAME, name);
initialValues.put(MODEL, model);
initialValues.put(YEAR, year);
return mDb.insert(DATABASE_TABLE, null, initialValues);
}
public long create(String name, String model, String year)
{
ContentValues initialValues = new ContentValues();
initialValues.put(NAME, name);
initialValues.put(MODEL, model);
initialValues.put(YEAR, year);
return this.mDb.insert(DATABASE_TABLE, null, initialValues);
}
public boolean deleteCar(long rowId)
{
return this.mDb.delete(DATABASE_TABLE, ROW_ID + "=" + rowId, null) > 0; //$NON-NLS-1$
}
public Cursor getAllCars()
{
return this.mDb.query(DATABASE_TABLE, new String[] { ROW_ID, NAME, MODEL, YEAR }, null, null, null, null, null);
}
public Cursor getCar(long rowId) throws SQLException
{
Cursor mCursor = this.mDb.query(true, DATABASE_TABLE, new String[] {ROW_ID, NAME, MODEL, YEAR}, ROW_ID + "=" + rowId,
null, null, null, null, null);
if(mCursor != null)
{
mCursor.moveToFirst();
}
return mCursor;
}
public boolean updateCar(long rowId, String name, String model, String year)
{
ContentValues args = new ContentValues();
args.put(NAME, name);
args.put(MODEL, model);
args.put(YEAR, year);
return this.mDb.update(DATABASE_TABLE, args, ROW_ID + "=" + rowId, null) >0;
}
}//end CarsDBAdapter class
对BoatsDBAdapter和CyclesDBAdapter类执行相同操作，但insert，update，delete方法名称不同。 这些是非DBAdapter类
Cars.java
public class Cars extends Activity
{
final Context context = this;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.cars);
CarsDBAdapter carsDB = new CarsDBAdapter(this);
//DBAdapter dbA = new DBAdapter(this);
carsDB.open();
long id;
id = carsDB.insertCars("Mercedes", "MERCDS", "2000");
id = carsDB.insertCars("BMW", "BMWTO", "1999");
carsDB.close();
carsDB.open();
Cursor c = carsDB.getAllCars();
if (c.moveToFirst())
{
do
{
DisplayContact(c);
} while (c.moveToNext());
}
carsDB.close();
Button btnMenu = (Button) findViewById(R.id.btnMenu);
btnMenu.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
Intent menuIntent = new Intent(context, VehiclesMenu.class);
startActivity(menuIntent);
}
});
}//end onCreate()
public void DisplayContact(Cursor c)
{
Toast.makeText(
this,
"id: " + c.getString(0) + "\n" + "Name: " + c.getString(1)
+ "\n" + "Model: " + c.getString(2) + "\n" + "Year: " + c.getString(3), Toast.LENGTH_LONG)
.show();
}
}
我为Boats.java和Cycles.java做了同样的事情，除了我在Boats.java中声明BoatsDBAdapter和在Cycles.java中声明CyclesDBAdapter
在Boats.java中
BoatsDBAdapter boatsDB = new BoatsDBAdapter(this);
boatsDB.open();
long id;
id = boatsDB.insertBoats("Jet-ski", "ERTYU", "2002");
id = boatsDB.insertBoats("Motor-boat", "MBCTY", "2003");
boatsDB.close();
boatsDB.open();
Cursor c = boatsDB.getAllBoats();
if (c.moveToFirst())
{
do
{
DisplayContact(c);
} while (c.moveToNext());
}
boatsDB.close();
和Cycles.java
CyclesDBAdapter cyclesDB = new CyclesDBAdapter(this);
cyclesDB.open();
long id;
id = cyclesDB.insertCycles("Mountain-bike", "ADCFG", "2004");
id = cyclesDB.insertCycles("Dirt-bike", "VBNGH", "2006");
cyclesDB.close();
cyclesDB.open();
Cursor c = cyclesDB.getAllCycles();
if (c.moveToFirst())
{
do
{
DisplayContact(c);
} while (c.moveToNext());
}
cyclesDB.close();
更新<！/强> 我对我的代码做了一些更新。我已将插入代码添加到CarsDBAdapter中。但插入代码不在上面链接的示例中。我删除了BoatsDBAdapter，CyclesDBAdapter，Boats和Cycles类，因为代码类似于CarsDBAdapter和Cars类。
答案 0 :(得分：0)
我会有三个看起来类似于以下的适配器（我只是将其作为一个演示版，但每个的想法是相同的
public class CarsDBAdapter {
public static final String ROW_ID = "_id";
public static final String NAME = "name";
public static final String MODEL = "model";
public static final String YEAR = "year";
private static final String DATABASE_TABLE = "cars";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
private final Context mCtx;
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DBAdapter.DATABASE_NAME, null, DBAdapter.DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
/**
* Constructor - takes the context to allow the database to be
* opened/created
*
* @param ctx
* the Context within which to work
*/
public CarsDBAdapter(Context ctx) {
this.mCtx = ctx;
}
/**
* Open the cars 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 CarsDBAdapter open() throws SQLException {
this.mDbHelper = new DatabaseHelper(this.mCtx);
this.mDb = this.mDbHelper.getWritableDatabase();
return this;
}
/**
* close return type: void
*/
public void close() {
this.mDbHelper.close();
}
/**
* Create a new car. If the car is successfully created return the new
* rowId for that car, otherwise return a -1 to indicate failure.
*
* @param name
* @param model
* @param year
* @return rowId or -1 if failed
*/
public long createCar(String name, String model, String year){
ContentValues initialValues = new ContentValues();
initialValues.put(NAME, name);
initialValues.put(MODEL, model);
initialValues.put(YEAR, year);
return this.mDb.insert(DATABASE_TABLE, null, initialValues);
}
/**
* Delete the car with the given rowId
*
* @param rowId
* @return true if deleted, false otherwise
*/
public boolean deleteCar(long rowId) {
return this.mDb.delete(DATABASE_TABLE, ROW_ID + "=" + rowId, null) > 0; //$NON-NLS-1$
}
/**
* Return a Cursor over the list of all cars in the database
*
* @return Cursor over all cars
*/
public Cursor getAllCars() {
return this.mDb.query(DATABASE_TABLE, new String[] { ROW_ID,
NAME, MODEL, YEAR }, null, null, null, null, null);
}
/**
* Return a Cursor positioned at the car that matches the given rowId
* @param rowId
* @return Cursor positioned to matching car, if found
* @throws SQLException if car could not be found/retrieved
*/
public Cursor getCar(long rowId) throws SQLException {
Cursor mCursor =
this.mDb.query(true, DATABASE_TABLE, new String[] { ROW_ID, NAME,
MODEL, YEAR}, ROW_ID + "=" + rowId, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
/**
* Update the car.
*
* @param rowId
* @param name
* @param model
* @param year
* @return true if the note was successfully updated, false otherwise
*/
public boolean updateCar(long rowId, String name, String model,
String year){
ContentValues args = new ContentValues();
args.put(NAME, name);
args.put(MODEL, model);
args.put(YEAR, year);
return this.mDb.update(DATABASE_TABLE, args, ROW_ID + "=" + rowId, null) >0;
}
}
所以我的主DBAdapter（负责在一个db中创建我的所有表）看起来像这样
public class DBAdapter {
public static final String DATABASE_NAME = "stuffIOwn"; //$NON-NLS-1$
public static final int DATABASE_VERSION = 1;
private static final String CREATE_TABLE_CARS =
"create table cars (_id integer primary key autoincrement, " //$NON-NLS-1$
+ CarsDBAdapter.NAME+ " TEXT," //$NON-NLS-1$
+ CarsDBAdapter.MODEL+ " TEXT," //$NON-NLS-1$
+ CarsDBAdapter.YEAR+ " TEXT" + ");"; //$NON-NLS-1$ //$NON-NLS-2$
private static final String CREATE_TABLE_BOATS = "create table boats (_id integer primary key autoincrement, " //$NON-NLS-1$
+BoatsDBAdapter.NAME+" TEXT," //$NON-NLS-1$
+BoatsDBAdapter.MODEL+" TEXT," //$NON-NLS-1$
+BoatsDBAdapter.YEAR+" TEXT"+ ");"; //$NON-NLS-1$ //$NON-NLS-2$
private static final String CREATE_TABLE_CYCLES = "create table cycles (_id integer primary key autoincrement, " //$NON-NLS-1$
+CyclesDBAdapter.NAME+" TEXT," //$NON-NLS-1$
+CyclesDBAdapter.MODEL+" TEXT," //$NON-NLS-1$
+CyclesDBAdapter.YEAR+" TEXT"+ ");"; //$NON-NLS-1$ //$NON-NLS-2$
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
/**
* Constructor
* @param ctx
*/
public DBAdapter(Context ctx)
{
this.context = ctx;
this.DBHelper = new DatabaseHelper(this.context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(CREATE_TABLE_CARS);
db.execSQL(CREATE_TABLE_BOATS);
db.execSQL(CREATE_TABLE_CYCLES);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
// Adding any table mods to this guy here
}
}
/**
* open the db
* @return this
* @throws SQLException
* return type: DBAdapter
*/
public DBAdapter open() throws SQLException
{
this.db = this.DBHelper.getWritableDatabase();
return this;
}
/**
* close the db
* return type: void
*/
public void close()
{
this.DBHelper.close();
}
}
DBAdapter类仅在应用程序首次启动时被调用，其唯一的责任是创建/升级表。对数据的所有其他访问都是通过单独的“适配器”类完成的。我发现这很有效，并没有创建我之前提到的版本问题。