我觉得Android开发人员关于在SQLite中保存数据的准则确实缺乏。我对多个表格的一般准则感到困惑。
我目前有两个管理器向UI公开(CRUD)两组不同的实体。
我:
在每个Manager中创建一个私有类SQLiteOpenHelper。每个Helper都有自己的onCreate用于自己的TABLE?
或
创建一个公共类SQLiteOpenHelper,它创建两个TABLE?
我没有看到使用一个在另一个之上的明显优势,但我看到它们都被使用了。 Android对此有何看法?
答案 0 :(得分:8)
以下示例代码创建了两个表。我还添加了用于创建和插入数据的代码。
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class MyDB {
public static final String KEY_ROWID = "_id";
public static final String KEY_FIRSTNAME = "ID";
public static final String KEY_LASTNAME = "CS";
public static final String KEY_DESIGNATION = "CN";
public static final String KEY_DN = "DN";
private static final String TAG = "MyDB";
private static final String DATABASE_NAME = "test.db";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE_ValidateUser_DriverInfo =
"create table tabletest1 (_id integer primary key autoincrement, "
+ "ID text not null, CS text not null, CN text not null, DN text not null);";
private static final String DATABASE_CREATE_ValidateUser_TripInfo =
"create table tabletest2 (_id integer primary key autoincrement, "
+ "TI text not null, PU text not null, LN text not null, FN text not null, Origin varchar not null, De text not null);";
private Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public MyDB(Context ctx) {
this.context = ctx;
DBHelper = new DatabaseHelper(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(DATABASE_CREATE_ValidateUser_DriverInfo);
db.execSQL(DATABASE_CREATE_ValidateUser_TripInfo);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion
+ " to " + newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS tabletest1");
db.execSQL("DROP TABLE IF EXISTS tabletest2");
onCreate(db);
}
}
public MyDB open() throws SQLException {
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close() {
DBHelper.close();
}
public long insertTitle(ContentValues initialValues, String TableName) {
return db.insert(TableName, null, initialValues);
}
}
使用以下代码插入所需活动的数据。
MyDB mmdb=new MyDB(getBaseContext());
mmdb.open();
initialValues = new ContentValues();
initialValues.put("ID", ID);
initialValues.put("CS", CS);
initialValues.put("CN", CN);
initialValues.put("DN", DN);
mmdb.insertTitle(initialValues, "tabletest1");
mmdb.close();