02数据库的设计

新建domain包和db包，domain包下存放User实体类。代码如下：

package com.dy.ustc.im.domain;import com.easemob.chat.EMContact;/** *  * 用户信息封装 *  * @author *  */public class User extends EMContact {private int unreadMsgCount;private String header;public int getUnreadMsgCount() {return unreadMsgCount;}public void setUnreadMsgCount(int unreadMsgCount) {this.unreadMsgCount = unreadMsgCount;}public String getHeader() {return header;}public void setHeader(String header) {this.header = header;}@Overridepublic int hashCode() {return 17 * getUsername().hashCode();}@Overridepublic boolean equals(Object o) {if (o == null || !(o instanceof User)) {return false;}return getUsername().equals(((User) o).getUsername());}@Overridepublic String toString() {return nick == null ? username : nick;}}

包含两部分内容：

一是用户的未读的消息的数目，而是用户的用户名。

特别留意下，本实体类重写了hashCode和equal方法，代码如下：

@Overridepublic int hashCode() {return 17 * getUsername().hashCode();}@Overridepublic boolean equals(Object o) {if (o == null || !(o instanceof User)) {return false;}return getUsername().equals(((User) o).getUsername());}

DbOpenHelper继承自：SQLiteOpenHelper，默认的有创建数据库和升级数据库的代码，在构造器中初始化，代码如下：

package com.dy.ustc.im.db;import com.dy.ustc.im.application.IMApplication;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DbOpenHelper extends SQLiteOpenHelper {private static final int DATABASE_VERSION = 1;private static DbOpenHelper instance; private static final String USERNAME_TABLE_CREATE = "CREATE TABLE "+ UserDao.TABLE_NAME + " ("+ UserDao.COLUMN_NAME_NICK +" TEXT, "+ UserDao.COLUMN_NAME_ID + " TEXT PRIMARY KEY);";private static final String INIVTE_MESSAGE_TABLE_CREATE = "CREATE TABLE "+ InviteMessgeDao.TABLE_NAME + " ("+ InviteMessgeDao.COLUMN_NAME_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "+ InviteMessgeDao.COLUMN_NAME_FROM + " TEXT, "+ InviteMessgeDao.COLUMN_NAME_GROUP_ID + " TEXT, "+ InviteMessgeDao.COLUMN_NAME_GROUP_Name + " TEXT, "+ InviteMessgeDao.COLUMN_NAME_REASON + " TEXT, "+ InviteMessgeDao.COLUMN_NAME_STATUS + " INTEGER, "+ InviteMessgeDao.COLUMN_NAME_ISINVITEFROMME + " INTEGER, "+ InviteMessgeDao.COLUMN_NAME_TIME + " TEXT); ";public DbOpenHelper(Context context) {super(context, getUserDatabaseName(), null, DATABASE_VERSION);}private static String getUserDatabaseName(){return IMApplication.getInstance().getUserName() + ".db";}public static DbOpenHelper getInstance(Context context) {if (instance == null) {instance = new DbOpenHelper(context.getApplicationContext());}return instance;}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(USERNAME_TABLE_CREATE);db.execSQL(INIVTE_MESSAGE_TABLE_CREATE);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}public void closeDB(){if (instance != null) {try {SQLiteDatabase db = instance.getWritableDatabase();db.close();} catch (Exception e) {e.printStackTrace();}instance = null;}}}

UserDao类封装增删改查的方法，代码如下：

package com.dy.ustc.im.db;import java.util.HashMap;import java.util.List;import java.util.Map;import com.dy.ustc.im.Constant;import com.dy.ustc.im.domain.User;import com.easemob.util.HanziToPinyin;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.text.TextUtils;public class UserDao {public static final String TABLE_NAME = "uers";public static final String COLUMN_NAME_ID = "username";public static final String COLUMN_NAME_NICK = "nick";public static final String COLUMN_NAME_IS_STRANGER = "is_stranger";private DbOpenHelper dbHelper;public UserDao(Context context) {dbHelper = DbOpenHelper.getInstance(context);}/** * 保存好友List *  * @param contactList */public void saveContactList(List<User> contactList) {SQLiteDatabase db = dbHelper.getWritableDatabase();if (db.isOpen()) {db.delete(TABLE_NAME, null, null);for (User user : contactList) {ContentValues values = new ContentValues();values.put(COLUMN_NAME_ID, user.getUsername());if (user.getNick() != null) {values.put(COLUMN_NAME_NICK, user.getNick());}db.replace(TABLE_NAME, null, values);}}}/** *  * 获取好友list *  * @return */public Map<String, User> getContactList() {SQLiteDatabase db = dbHelper.getWritableDatabase();Map<String, User> users = new HashMap<String, User>();if (db.isOpen()) {Cursor cursor = db.rawQuery("select * from " + TABLE_NAME /* + " desc" */, null);while (cursor.moveToNext()) {String username = cursor.getString(cursor.getColumnIndex(COLUMN_NAME_ID));String nick = cursor.getString(cursor.getColumnIndex(COLUMN_NAME_NICK));User user = new User();user.setUsername(username);String headerName = null;if (!TextUtils.isEmpty(user.getNick())) {headerName = user.getNick();} else {headerName = user.getUsername();}if (username.equals(Constant.NEW_FRIENDS_USERNAME)|| username.equals(Constant.GROUP_USERNAME)) {user.setHeader("");} else if (Character.isDigit(headerName.charAt(0))) {user.setHeader("#");} else {user.setHeader(HanziToPinyin.getInstance().get(headerName.substring(0, 1)).get(0).target.substring(0, 1).toUpperCase());char header = user.getHeader().toLowerCase().charAt(0);if (header < 'a' || header > 'z') {user.setHeader("#");}}users.put(username, user);}cursor.close();}return users;}/** * 删除一个联系人 *  * @param username */public void deleteContact(String username) {SQLiteDatabase db = dbHelper.getWritableDatabase();if (db.isOpen()) {db.delete(TABLE_NAME, COLUMN_NAME_ID + " = ?",new String[] { username });}}/** *  * 保存一个联系人 *  * @param user */public void saveContact(User user) {SQLiteDatabase db = dbHelper.getWritableDatabase();ContentValues values = new ContentValues();values.put(COLUMN_NAME_ID, user.getUsername());if (user.getNick() != null) {values.put(COLUMN_NAME_NICK, user.getNick());}if (db.isOpen()) {db.replace(TABLE_NAME, null, values);}}}

本案例的代码不熟悉没关系，后面会用到，到时候自然明白。