我目前在android资源文件夹中有一个数据库，保存了三个名为DATABASE_TABLE，DATABASE_TABLE2和DATABASE_TABLE3的数据库表。到目前为止，我已经实现了所有我需要的“DATABASE_TABLE”，我想避免重复DATABASE_TABLE2和DATABASE_TABLE3的代码我想知道这样做的最佳方法是什么？任何有用的建议都将不胜感激。
package com.topscore.db;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import com.topscore.core.Question;
public class Database {
String DB_PATH = "/data/data/com.topscore/databases/";
private static final String DATABASE_NAME = "tsp";
private static final int DATABASE_VERSION = 1;
private final Context mContext;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
private static final String DATABASE_TABLE = "CHEMISTRY";
private static final String DATABASE_TABLE2 = "MATH";
private static final String DATABASE_TABLE3 = "PHYSICS";
public static final String KEY_ID = "QuestionId";
public static final String KEY_TYEP = "ExamType";
public static final String KEY_YEAR = "Year";
public static final String KEY_SUBJECT = "Subject";
public static final String KEY_QUESTION = "Question";
public static final String KEY_ANSWERONE = "Answer1";
public static final String KEY_ANSWERTWO = "Answer2";
public static final String KEY_ANSWERTHREE = "Answer3";
public static final String KEY_ANSWERFOUR = "Answer4";
public static final String KEY_ANSWERFIVE = "Answer5";
public static final String KEY_CURRECTANSWER = "CorrectAnswer";
public Database(Context context) {
mContext = context;
DBHelper = new DatabaseHelper(mContext);
}
/*
* Database helper class which fires events on database open/create/upgrade
*/
private static class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// db.execSQL(DATABASE_CREATE_ITEMS);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE_TOPSCORE);
}
}
public Database open() throws SQLException {
db = DBHelper.getWritableDatabase();
return this;
}
public void close() {
DBHelper.close();
}
/*
* Insert Dairy
*/
public long insertDairy(long time, String note) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_TYEP, note);
initialValues.put(KEY_YEAR, time);
initialValues.put(KEY_SUBJECT, System.currentTimeMillis());
return db.insert(DATABASE_TABLE_TOPSCORE, null, initialValues);
}
/*
* Update Dairy
*/
public boolean UpdateDairy(long time, String note, int id) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_TYEP, note);
initialValues.put(KEY_YEAR, time);
initialValues.put(KEY_SUBJECT, System.currentTimeMillis());
return db.update(DATABASE_TABLE_TOPSCORE, initialValues, KEY_ID + "="
+ id, null) > 0;
}
/*
* Returns all the dairys from the table memory
*/
public List<Question> getAllDairys(String year, String type, String sub) {
year = year.replaceAll("'", "''");
type = type.replaceAll("'", "''");
sub = sub.replaceAll("'", "''");
List<Question> list = new ArrayList<Question>();
Cursor _cursor = db.query(true, DATABASE_TABLE_TOPSCORE, null, KEY_YEAR
+ " = '" + year + "' AND " + KEY_TYEP + " = '" + type
+ "' AND " + KEY_SUBJECT + " = '" + sub + "'", null, null,
null, KEY_ID +" ASC", null);
if (_cursor != null) {
_cursor.moveToFirst();
int count = _cursor.getCount();
Question question;
List<String> optionslist;
for (int i = 0; i < count; i++) {
_cursor.moveToPosition(i);
question = new Question();
question.setId(_cursor.getInt(0));
question.setType(_cursor.getString(1).trim());
String pyear = _cursor.getString(2).trim();
try {
question.setYear(Integer.parseInt(pyear));
} catch (Exception e) {
}
question.setSubject(_cursor.getString(3).trim());
question.setQuestion(_cursor.getString(4).trim());
optionslist = new ArrayList<String>();
optionslist.add(_cursor.getString(4).trim());
if (_cursor.getString(5).trim().length() > 0) {
optionslist.add(_cursor.getString(5).trim());
if (_cursor.getString(5).trim().equals(
_cursor.getString(10).trim())) {
question.setCurretAnswer(1);
}
}
if (_cursor.getString(6).trim().length() > 0) {
optionslist.add(_cursor.getString(6).trim());
if (_cursor.getString(6).trim().equals(
_cursor.getString(10).trim())) {
question.setCurretAnswer(2);
}
}
if (_cursor.getString(7).trim().length() > 0) {
optionslist.add(_cursor.getString(7).trim());
if (_cursor.getString(7).trim().equals(
_cursor.getString(10).trim())) {
question.setCurretAnswer(3);
}
}
if (_cursor.getString(8).trim().length() > 0) {
optionslist.add(_cursor.getString(8).trim());
if (_cursor.getString(8).trim().equals(
_cursor.getString(10).trim())) {
question.setCurretAnswer(4);
}
}
if (_cursor.getString(9).trim().length() > 0) {
optionslist.add(_cursor.getString(9).trim());
if (_cursor.getString(9).trim().equals(
_cursor.getString(10).trim())) {
question.setCurretAnswer(5);
}
}
question.setChoiceList(optionslist);
list.add(question);
}
}
return list;
}
/*
* Returns dairy from the table memory
*/
public Question getDairyWithId(int id) {
Question dairy = new Question();
Cursor _cursor = db.query(true, DATABASE_TABLE_TOPSCORE, null, KEY_ID
+ "=" + id, null, null, null, null, null);
if (_cursor != null) {
dairy = new Question();
_cursor.moveToFirst();
}
return dairy;
}
/*
* Returns dairy from the table memory
*/
public String[] getAllSubjects(int id) {
String string[] = null;
String key = "";
if (id == 3) {
key = KEY_SUBJECT;
} else if (id == 1) {
key = KEY_TYEP;
} else if (id == 2) {
key = KEY_YEAR;
}
Cursor _cursor = db.query(true, DATABASE_TABLE_TOPSCORE, null, null,
null, key, null, null, null);
if (_cursor != null && _cursor.getCount() > 0) {
_cursor.moveToFirst();
int count = _cursor.getCount();
string = new String[count];
for (int i = 0; i < count; i++) {
string[i] = _cursor.getString(id);
}
}
return string;
}
public boolean deleteDairy(int id) {
return db.delete(DATABASE_TABLE_TOPSCORE, KEY_ID + "=" + id, null) > 0;
}
/**
* Creates a empty database on the system and rewrites it with your own
* database.
* */
public void createDataBase() {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
// By calling this method and empty database will be created into
// the default system path
// of your application so we are gonna be able to overwrite that
// database with our database.
DBHelper.getReadableDatabase();
try {
copyDataBase();
} catch (Exception e) {
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each
* time you open the application.
*
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DATABASE_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
// database does't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created
* empty database in the system folder, from where it can be accessed and
* handled. This is done by transfering bytestream.
* */
private void copyDataBase() {
try {
// Open your local db as the input stream
InputStream myInput = mContext.getAssets().open("TopScoreDB");
// Path to the just created empty db
String outFileName = DB_PATH + DATABASE_NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
} catch (Exception e) {
}
}
}
答案 0 :(得分：0)
我和@Dave Newton在一起 - 如果三个表在结构上完全相同，为什么有三个表呢？
为什么不在一个现有的表中添加一个字段，例如“SubjectType”，它引用了物理，化学，数学等？
然后，您可以使用该字段对问题进行排序和提取吗？