android开发笔记（2）——简单的数据存储

1、数据库管理

继承自SQLiteOpenHelper类，实现数据库的创建、升级、增删查改方法

<pre name="code" class="java">/** *  */package com.zhe.moodpulse.db;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;/** * @author Administrator * */public class DBManager extends SQLiteOpenHelper {      private static final String DB_NAME = "moodpulse.db";    private static final int DB_VERSION = 1;          private static final String INIT_DB = UserTable.CREATE_TABLE;          private static final String UPGRADE_DB = "";/** * @param context */public DBManager(Context context) {super(context, DB_NAME, null, DB_VERSION);// TODO Auto-generated constructor stub}/* (non-Javadoc) * @see android.database.sqlite.SQLiteOpenHelper#onCreate(android.database.sqlite.SQLiteDatabase) */@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(INIT_DB);    ContentValues values = new ContentValues();    values.put(UserTable.USER_CODE, "user_" + System.currentTimeMillis());      values.put(UserTable.USER_PASSWORD, "");      values.put(UserTable.IS_VALID, 0);     db.insert(UserTable.TABLE_NAME,null,values);        }public void insert(String tableName, ContentValues values) {SQLiteDatabase db = getWritableDatabase();          db.insert(tableName, null, values);          db.close();  }public void delete(String tableName, String whereClause, String[] whereArgs) {SQLiteDatabase db = getWritableDatabase(); db.delete(tableName, whereClause, whereArgs);           db.close();  }public Cursor query(String tableName, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy) {SQLiteDatabase db = getWritableDatabase();          Cursor c = db.query(tableName, columns, selection, selectionArgs, groupBy, having, orderBy);          return c;  }/* (non-Javadoc) * @see android.database.sqlite.SQLiteOpenHelper#onUpgrade(android.database.sqlite.SQLiteDatabase, int, int) */@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL(UPGRADE_DB);}}

2、对于每一张表，创建一个对应的类，描述其表名、字段以及创建该表的sql语句

<pre name="code" class="java">package com.zhe.moodpulse.db;public class UserTable {    public static final String TABLE_NAME = "user_table";    public static final String _ID = "_id";    public static final String USER_CODE = "user_code";    public static final String USER_NICK = "user_nick";    public static final String USER_PASSWORD = "user_password";    public static final String REGISTER_DATE = "register_date";    public static final String HEAD_IMG = "user_head";    public static final String ONLINE_STATUS = "online_status";    public static final String IS_VALID = "is_valid";    public static final String CREATE_TABLE = " create table " + TABLE_NAME + "("    + _ID + " integer primary key autoincrement, "             + USER_CODE + " text, "    + USER_NICK + " text, "            + USER_PASSWORD + " text, "    + REGISTER_DATE + " smalldatetime, "      + HEAD_IMG + " image, "    + ONLINE_STATUS + " text, "      + IS_VALID + " int) ";  }

3、在界面控件的响应中调用相应的方法

首先实例化一个数据库管理器对象：<pre name="code" class="java">DBManager helper = new DBManager(getApplicationContext());

4、一些小技巧

</pre><pre name="code" class="java">1）获取当前时间中的年月日时分秒的信息

<pre name="code" class="java">package com.zhe.utils;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Locale;public class TimeUtils {private static SimpleDateFormat allFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss",Locale.CHINA);private static SimpleDateFormat yearFormat = new SimpleDateFormat("yyyy",Locale.CHINA);private static SimpleDateFormat monthFormat = new SimpleDateFormat("MM",Locale.CHINA);private static SimpleDateFormat dayFormat = new SimpleDateFormat("dd",Locale.CHINA);private static SimpleDateFormat hourFormat = new SimpleDateFormat("hh",Locale.CHINA);private static SimpleDateFormat minFormat = new SimpleDateFormat("mm",Locale.CHINA);public static String getAll(Date now){ return allFormat.format(now);}public static String getYear(Date now){ return yearFormat.format(now);}public static String getMonth(Date now){ return monthFormat.format(now);}public static String getDate(Date now){ return dayFormat.format(now);}public static String getHour(Date now){ return hourFormat.format(now);}public static String getMinute(Date now){ return minFormat.format(now);}}

2）在app中保存用户信息，在任意位置能够调用

<pre name="code" class="java"><span style="white-space:pre">private SharedPreferences sp;</span>

<span style="white-space:pre"></span>private void initialUser() {sp = this.getSharedPreferences("userInfo", Context.MODE_PRIVATE);String userName = sp.getString("user_name", "");if(userName == "") checkDefaultUser();}private void checkDefaultUser() {         Cursor res = helper.query(UserTable.TABLE_NAME, null, null, null, null, null, null);           res.moveToNext();        String userName = res.getString(1);                        Editor editor = sp.edit();          editor.putString("user_name", userName);          editor.putString("password","");          editor.commit();}

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