我在 Android 中关注这个示例多表 SQLite DB 适配器？关于在一个数据库中存储多个表。
我创建了 4 个 DBAdapter（DBAdapter、CarsDBAdapter、BoatsDBAdapter 和 CyclesDBAdapter）。但是在其中一个 DBAdapter 中，我在 db 适配器中创建了 3 个表。然后我为其他 3 个数据库适配器创建了 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。我将不胜感激提供的任何帮助。
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 类做了同样的事情，但插入、更新、删除方法名称不同。这些是非 DBAdapter 类
汽车.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();
}
}
我对 Boats.java 和 Cycles.java 做了同样的事情，只是我在 Boats.java 中声明了 BoatsDBAdapter，在 Cycles.java 中声明了 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();
在 Cycles.java 中
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！ 我对我的代码进行了一些更新。我已将插入代码添加到 CarsDBAdapter 中。但是插入代码不在上面链接中的示例中。我删除了 BoatsDBAdapter、CyclesDBAdapter、Boats 和 Cycles 类，因为代码类似于 CarsDBAdapter 和 Cars 类。