我在SQLite数据库中共有5个表如果我在 DatabaseHalper.class 中创建一个全部表并执行所有 CRUD（（创建，读取，更新和删除））< / strong>在此课程中操作，这看起来像大数据
Table Is Like: Company, Contact, ToDo。等
DatabaseHalper.class 第二个创建另一个类就像使用表名 ComapnyDB.class 一样
在此课程中，我想为 Company 表执行CRUD操作，同时所有查询都针对公司表执行
Contact 表的第3个相同。在 DatabaseHalper.class 中创建表格
并在此类中创建一个新类，如 Contact.class ，执行所有CURD操作并执行其他操作
所以我的代码分为不同的不同类
DatabseHalper.class ，在此课程中我将创建数据库表。 DatabaseHalper.class
public class DatabaseHelper extends SQLiteOpenHelper {
// Logcat tag
private static final String LOG = "DatabaseHelper";
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "contactsManager";
//Tables Name
private static final String COMPANY = "company";
private static final String CONTACTS = "contacts";
private static final String EVENT = "event";
private static final String TODO = "todo";
private static final String USER = "user";
// Common column names
private static final String KEY_ID = "id";
//Companies Table Column Name
private static final String KEY_COMPANY_ID = "CompanyId";
private static final String KEY_COMPANY_REFERENCE_ID = "ReferenceId";
private static final String KEY_COMPANY_NAME = "CompanyName";
private static final String KEY_COMPANY_WEBSITE = "CompanyWebsite";
private static final String KEY_COMPANY_EMAIL = "CompanyEmail";
private static final String KEY_COMPANY_PHONE_HOME = "CompanyPhoneHome";
private static final String KEY_COMPANY_PHONE_PRIMARY = "CompanyPhonePrimary";
private static final String KEY_COMPANY_ADDRESS1 = "CompanyAddress";
private static final String KEY_COMPANY_ADDRESS2 = "CompanyAddressSecondary";
private static final String KEY_COMPANY_CITY = "CompanyCity";
private static final String KEY_COMPANY_STATE = "CompanyState";
private static final String KEY_COMPANY_ZIP = "CompanyZip";
private static final String KEY_COMPANY_COUNTRY = "CompanyCountry";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Table Create Statements
// Todo table create statement
private static final String CREATE_TABLE_COMPANY = "CREATE TABLE "
+ COMPANY + "(" + KEY_ID + " INTEGER PRIMARY KEY," + KEY_COMPANY_ID + " INTEGER,"
+ KEY_COMPANY_REFERENCE_ID + " INTEGER,"
+ KEY_COMPANY_NAME + " VARCHAR,"
+ KEY_COMPANY_WEBSITE + "VARCHAR,"
+ KEY_COMPANY_EMAIL + "VARCHAR,"
+ KEY_COMPANY_PHONE_HOME + "VARCHAR,"
+ KEY_COMPANY_PHONE_PRIMARY + "VARCHAR,"
+ KEY_COMPANY_ADDRESS1 + "VARCHAR,"
+ KEY_COMPANY_ADDRESS2 + "VARCHAR,"
+ KEY_COMPANY_CITY + "VARCHAR,"
+ KEY_COMPANY_STATE + "VARCHAR,"
+ KEY_COMPANY_ZIP + "INTEGER,"
+ KEY_COMPANY_COUNTRY + "VARCHAR" + ")";
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_COMPANY);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + COMPANY);
}
}
现在我要创建 CompanyDB.class CURD 操作但如何访问 DatabaseHelper.class 在 Company.class 。
提前致谢：）
答案 0 :(得分：1)
以下是将表格与DatabaseHelper分开的示例： -
public class ContactDB {
public static final String TBNAME = "contact";
public static final String COL_ID = BaseColumns._ID;
public static final String COL_NAME = "contact_name";
public static final String COL_EMAIL = "contact_email";
public static String getTableCreatSQL() {
return "CREATE TABLE IF NOT EXISTS " + TBNAME + "(" +
COL_ID + " INTEGER PRIMARY KEY, " +
COL_NAME + " TEXT," +
COL_EMAIL + " TEXT" +
")";
}
public static long addContact(SQLiteDatabase db, String contact_name, String contact_email) {
ContentValues cv = new ContentValues();
cv.put(COL_NAME,contact_name);
cv.put(COL_EMAIL,contact_email);
return db.insert(TBNAME,null,cv);
}
public static Cursor getAllContacts(SQLiteDatabase db) {
return db.query(TBNAME,null,null,null,null,null,COL_NAME + " ASC," + COL_EMAIL + " ASC");
}
}
public class CompanyDB {
public static final String TBNAME = "company";
public static final String COL_ID = BaseColumns._ID;
public static final String COL_NAME = "company_name";
public static String getTableCreateSQL() {
return "CREATE TABLE IF NOT EXISTS " + TBNAME + "(" +
COL_ID + " INTEGER PRIMARY KEY," +
COL_NAME + " TEXT" +
")";
}
public static long addCompany(SQLiteDatabase db, String company_name ) {
ContentValues cv = new ContentValues();
cv.put(COL_NAME,company_name);
return db.insert(TBNAME,null,cv);
}
public static Cursor getAllCompanies(SQLiteDatabase db) {
return db.query(TBNAME,null,null,null,null,null,COL_NAME + " ASC");
}
}
public class DBHelper extends SQLiteOpenHelper {
public static final String DBNAME = "mydatabase";
public static final int DBVERSION = 1;
private static SQLiteDatabase mDB;
public DBHelper(Context context) {
super(context, DBNAME, null, DBVERSION);
mDB = this.getWritableDatabase();
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CompanyDB.getTableCreateSQL());
db.execSQL(ContactDB.getTableCreatSQL());
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
public class MainActivity extends AppCompatActivity {
Cursor mAllContacts;
Cursor mAllCompanies;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SQLiteDatabase mDB = new DBHelper(this).getWritableDatabase();
CompanyDB.addCompany(mDB,"mycompany");
ContactDB.addContact(mDB,"Fred","Fred@email.com");
ContactDB.addContact(mDB,"Bert","bertbloggins@bloggings.moc");
mAllCompanies = CompanyDB.getAllCompanies(mDB);
while (mAllCompanies.moveToNext()) {
Log.d("COMPANY",
"Company Name = " +
mAllCompanies.getString(
mAllCompanies.getColumnIndex(
CompanyDB.COL_NAME
)
)
);
}
Cursor mAllContacts = ContactDB.getAllContacts(mDB);
while (mAllContacts.moveToNext()) {
Log.d("CONTACT",
"Contact Name = " +
mAllContacts.getString(
mAllContacts.getColumnIndex(
ContactDB.COL_NAME
)
) +
" Email = " +
mAllContacts.getString(
mAllContacts.getColumnIndex(
ContactDB.COL_EMAIL
)
)
);
}
}
@Override
protected void onDestroy() {
super.onDestroy();
mAllCompanies.close();
mAllContacts.close();
}
}
输出将是石灰（首次运行）： -
04-02 09:09:42.556 1497-1497/so49607475_splittableclasses.so49607475_splittableclasses D/COMPANY: Company Name = mycompany
04-02 09:09:42.556 1497-1497/so49607475_splittableclasses.so49607475_splittableclasses D/CONTACT: Contact Name = Bert Email = bertbloggins@bloggings.moc
Contact Name = Fred Email = Fred@email.com