Android Sqlite数据库 增删改查应用

一、Sqlite数据库介绍二、Sqlite数据库增删改查在Android开发中应用Sqlite数据库数据常用类型介绍1、每个存储在 SQLite 数据库中的值都具有以下存储类之一：NULL ：值是一个 NULL 值。INTEGER:值是一个带符号的整数，根据值的大小存储在 1、2、3、4、6 或 8 字节中。REAL :值是一个浮点值，存储为 8 字节的 IEEE 浮点数字TEXT:值是一个文本字符串，使用数据库编码（UTF-8、UTF-16BE或 UTF-16LE）存储BLOB:值是一个blob 数据，完全根据它的输入存储。2、Sqlite亲和类型

亲和类型	描述
TEXT	数值型数据在被插入之前，需要先被转换为文本格式，之后再插入到目标字段中。
NUMERIC	当文本数据被插入到亲缘性为NUMERIC的字段中时，如果转换操作不会导致数据信息丢失以及完全可逆，那么SQLite就会将该文本数据转换为INTEGER或REAL类型的数据，如果转换失败，SQLite仍会以TEXT方式存储该数据。对于NULL或BLOB类型的新数据，SQLite将不做任何转换，直接以NULL或BLOB的方式存储该数据。需要额外说明的是，对于浮点格式的常量文本，如"30000.0"，如果该值可以转换为INTEGER同时又不会丢失数值信息，那么SQLite就会将其转换为INTEGER的存储方式。
INTEGER	对于亲缘类型为INTEGER的字段，其规则等同于NUMERIC，唯一差别是在执行CAST表达式时。
REAL	其规则基本等同于NUMERIC，唯一的差别是不会将"30000.0"这样的文本数据转换为INTEGER存储方式。
NONE	不做任何的转换，直接以该数据所属的数据类型进行存储。

INTEGER : INT , INTEGER ,TINYINT , SMALLINT ,MEDIUMINT ,BIGINT ,UNSIGNED BIG INT ,INT2 ,INT8TEXT: CHARACTER(20) 、VARCHAR(255)、VARYING CHARACTER(255)、NCHAR(55)、NATIVECHARACTER(70)、NVARCHAR(100)、TEXT、CLOBNONE：BLOBno datatype specifiedREAL：REAL、DOUBLE、DOUBLEPRECISION、FLOATNUMERIC：NUMERIC、DECIMAL(10,5)、BOOLEAN、DATE、DATETIMESQLite没有单独的 Boolean 存储类。相反，布尔值被存储为整数 0（false）和 1（true）。Sqlite数据库在Android应用中使用Android 平台内置了丰富的API可以供开发者调用SQLIte数据库1、首先继承SQLiteOpenHelper 类 并实现里面的onCreate(SQLiteDatabase db)方法和onUpgrade(SQLiteDatabase db,intoldVersion,intnewVersion)onCreate 方法是应用程创建数据库及其表onUpgrade 数据库版更新调用2、创建一个单例类LeDBManager 管理数据的增删改查public class LeDBManager {private static Context mContext;private LeDBOpenHelper mDbOpenHelper;private LeDBManager(Context context) {mDbOpenHelper = new LeDBOpenHelper(context);}private static class SingletonHolder {private static final LeDBManager INSTANCE = new LeDBManager(mContext);}public static final LeDBManager getInstance(Context context) {mContext = context;return SingletonHolder.INSTANCE;}//....................

}

代码的具体实现如下：LeDBOpenHelper 类实现

public class LeDBOpenHelper extends SQLiteOpenHelper {private static final int DB_VERSION = 1 ;  // 数据库版本private static final String DB_NAME = "leNet.db" ; // 数据库名称public LeDBOpenHelper(Context context) {super(context, DB_NAME, null, DB_VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(createDownloadTable);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}public static final String TABLE_DOWNLOAD = "table_download" ;public static final String DOWNLOAD_NAME = "download_name" ;public static final String DOWNLOAD_URL = "download_url" ;public static final String DOWNLOAD_PATH = "download_path" ;public static final String DOWNLOAD_TOTAL_SIZE = "download_total_size" ;public static final String DOWNLOAD_DOWNLOAD_SIZE = "download_download_size" ;public static final String DOWNLOAD_STATUS = "download_status" ;private String createDownloadTable = "create table  if not exists table_download (" +"id integer primary key autoincrement," +"download_name varchar ," +"download_url varchar ," +"download_path varchar ," +"download_total_size long ," +"download_download_size long," +"download_status smallint" +")" ;}

LeDBManager 中实现数据的增删改查

/*** Created by familylove on 2017/4/26.* 数据库* 增* 删* 改* 查* 管理类*/public class LeDBManager {private static Context mContext;private LeDBOpenHelper mDbOpenHelper;private LeDBManager(Context context) {mDbOpenHelper = new LeDBOpenHelper(context);}private static class SingletonHolder {private static final LeDBManager INSTANCE = new LeDBManager(mContext);}public static final LeDBManager getInstance(Context context) {mContext = context;return SingletonHolder.INSTANCE;}/*** 插入数据** @param bean*/public void insertDownload(DownloadBean bean) {if (bean == null)return;SQLiteDatabase db = mDbOpenHelper.getWritableDatabase();db.beginTransaction();if (!isExistsDownload(db, bean.getUrl())) {db.insert(LeDBOpenHelper.TABLE_DOWNLOAD, null, bean.toContentValues(bean));}db.setTransactionSuccessful();db.endTransaction();if (db != null)db.close();}/*** 删除数据* @param tag*/public boolean deleteDownload(String tag){boolean flag = false ;if (TextUtils.isEmpty(tag))return flag;SQLiteDatabase db = mDbOpenHelper.getWritableDatabase() ;db.beginTransaction();int deleteFlag = db.delete(LeDBOpenHelper.TABLE_DOWNLOAD,LeDBOpenHelper.DOWNLOAD_URL+" = ? ",new String[]{tag}) ;db.setTransactionSuccessful();db.endTransaction();if (db!=null)db.close();if (deleteFlag==1)flag = true ;else if (deleteFlag==0)flag = false ;return flag ;}/*** 更新数据** @param tag* @param totalSize* @param downloadSize* @param status*/public void updateDownload(String tag, long totalSize, long downloadSize, int status) {SQLiteDatabase db = mDbOpenHelper.getWritableDatabase();db.beginTransaction();if (isExistsDownload(db, tag)) {ContentValues updateCV = new ContentValues();updateCV.put(LeDBOpenHelper.DOWNLOAD_TOTAL_SIZE, totalSize);updateCV.put(LeDBOpenHelper.DOWNLOAD_DOWNLOAD_SIZE, downloadSize);updateCV.put(LeDBOpenHelper.DOWNLOAD_STATUS, status);db.update(LeDBOpenHelper.TABLE_DOWNLOAD, updateCV, LeDBOpenHelper.DOWNLOAD_URL + " = ?", new String[]{tag});}db.setTransactionSuccessful();db.endTransaction();if (db != null)db.close();db = null;}/*** 判断数据是否存在* @param db* @param tag* @return*/private boolean isExistsDownload(SQLiteDatabase db, String tag) {boolean flag = false;String sql = "select * from " + LeDBOpenHelper.TABLE_DOWNLOAD + " where " + LeDBOpenHelper.DOWNLOAD_URL + " = ? ";Cursor cursor = db.rawQuery(sql, new String[]{tag});if (cursor != null && cursor.getCount() > 0) {flag = true;} else {flag = false;}if (cursor != null)cursor.close();return flag;}/*** 数据查询* @param tag* @return*/public DownloadBean queryOneDownload(String tag) {DownloadBean bean = null;SQLiteDatabase db = mDbOpenHelper.getReadableDatabase();Cursor cursor = db.rawQuery("select * from " + LeDBOpenHelper.TABLE_DOWNLOAD + " where " + LeDBOpenHelper.DOWNLOAD_URL + " = ?",new String[]{tag});if (cursor != null && cursor.getCount() > 0) {if (cursor.moveToNext()) {bean = cursorToDownloadBean(cursor);}}if (cursor != null)cursor.close();if (db != null)db.close();return bean;}/*** 计算表 tableName 数据总量* @param tableName* @return 数据表数据总条数*/public int countDownloadBeans(String tableName){int count = 0 ;SQLiteDatabase db = mDbOpenHelper.getReadableDatabase() ;Cursor cursor = db.rawQuery("select count(*) from "+tableName,null) ;if (cursor!=null && cursor.getCount()>0){cursor.moveToFirst() ;count = cursor.getInt(0) ;}return count ;}/*** cursor to bean* @param cursor* @return*/private DownloadBean cursorToDownloadBean(Cursor cursor) {DownloadBean bean = new DownloadBean();bean.setStatus(cursor.getInt(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_STATUS)));bean.setDownloadSize(cursor.getLong(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_DOWNLOAD_SIZE)));bean.setTotalSize(cursor.getLong(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_TOTAL_SIZE)));bean.setUrl(cursor.getString(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_URL)));bean.setName(cursor.getString(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_NAME)));bean.setPath(cursor.getString(cursor.getColumnIndex(LeDBOpenHelper.DOWNLOAD_PATH)));return bean;}}

DownloadBean类

public class DownloadBean implements Serializable {private String name;private String path;private String url;private int status = 0;private long totalSize;private long downloadSize;public long getDownloadSize() {return downloadSize;}public void setDownloadSize(long downloadSize) {this.downloadSize = downloadSize;}public long getTotalSize() {return totalSize;}public void setTotalSize(long totalSize) {this.totalSize = totalSize;}public DownloadBean() {}public DownloadBean(String name, String path, String url) {this.name = name;this.path = path;this.url = url;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPath() {return path;}public void setPath(String path) {this.path = path;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public int getStatus() {return status;}public void setStatus(int status) {this.status = status;}@Overridepublic String toString() {return "DownloadBean{" +"name='" + name + '\'' +", path='" + path + '\'' +", url='" + url + '\'' +", status=" + status +", totalSize=" + totalSize +", downloadSize=" + downloadSize +'}';}public ContentValues toContentValues(DownloadBean bean) {ContentValues cv = new ContentValues();cv.put(LeDBOpenHelper.DOWNLOAD_STATUS, bean.getStatus());cv.put(LeDBOpenHelper.DOWNLOAD_DOWNLOAD_SIZE, bean.getDownloadSize());cv.put(LeDBOpenHelper.DOWNLOAD_TOTAL_SIZE, bean.getTotalSize());cv.put(LeDBOpenHelper.DOWNLOAD_PATH, bean.getPath());cv.put(LeDBOpenHelper.DOWNLOAD_URL, bean.getUrl());cv.put(LeDBOpenHelper.DOWNLOAD_NAME, bean.getName());return cv;}}