android 数据库操作
2016-11-23 08:42
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版权声明：本文为博主原创文章，未经博主允许不得转载。
Android的数据库是用Sqlite3，关于增删改查的语句，其实与别的数据是区别并的大，网上也有很多，所以就不说这个问题。
这次主要是写写我在项目中用到数据库编码习惯。
以增删改查Book为例，先是结构：
跟着看Book类：
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package com.lxb.dbdemo.model;
public class Book {
private int id; // ID
private String name; // 名称
private float price; // 价格
private boolean canSale; // 是否可售
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public boolean isCanSale() {
return canSale;
}
public void setCanSale(boolean canSale) {
this.canSale = canSale;
}
@Override
public String toString() {
return "Book [id=" + id + ", name=" + name + ", price=" + price
+ ", canSale=" + canSale + "]";
}
}
然后是比较重要的继承自SQLiteOpenHelper的类，这里主要是建表及升级数据库操作（升级数据库只要把数据库版本号往上提就行）：
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package com.lxb.dbdemo.db;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class BookDBHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "book_db"; // 数据库名称
private static final int DATABASE_VERSION = 1; // 数据库版本
public static final String BOOK_TABLE = "book_table"; // 书表名
public static final String BOOK_ID = "book_id"; // 书ID
public static final String BOOK_NAME = "book_name"; // 书名
public static final String BOOK_PRICE = "book_price"; // 书价格
public static final String BOOK_CAN_SALE = "book_cansale"; // 是否可售
public BookDBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// 建表操作
StringBuilder sb = new StringBuilder();
sb.append("CREATE TABLE IF NOT EXISTS " + BOOK_TABLE + "(");
sb.append(BOOK_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,");
sb.append(BOOK_NAME + " VARCHAR(100),");
sb.append(BOOK_PRICE + " VARCHAR(100),");
sb.append(BOOK_CAN_SALE + " INTEGER)");
db.execSQL(sb.toString());
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + BOOK_TABLE);
onCreate(db);
}
}
接下来是一个Dao类，实现了增删改查的方法等：
[java]
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package com.lxb.dbdemo.db.dao;
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.lxb.dbdemo.db.BookDBHelper;
import com.lxb.dbdemo.model.Book;
public class BookDao {
private BookDBHelper helper;
private SQLiteDatabase db; // 数据库对象
public BookDao(Context context) {
helper = new BookDBHelper(context);
}
/**
* 打开数据库
*/
public void open() {
if(db == null || !db.isOpen()) {
db = helper.getWritableDatabase();
}
}
/**
* 关闭数据库
*/
public void close() {
db.close();
db = null;
}
/**
* 检查数据库是否可用
* @return
*/
private boolean checkDb() {
open();
if(db != null && db.isOpen()) {
return true;
}
return false;
}
/**
* 保存
* @param book
* @return
*/
public int saveBook(Book book) {
ContentValues values = new ContentValues();
values.put(BookDBHelper.BOOK_NAME, book.getName());
values.put(BookDBHelper.BOOK_PRICE, book.getPrice());
values.put(BookDBHelper.BOOK_CAN_SALE, book.isCanSale());
if(checkDb()) {
long id = db.insert(BookDBHelper.BOOK_TABLE, BookDBHelper.BOOK_ID, values);
return Integer.parseInt(id + "");
}
return -1;
}
/**
* 根据ID删除
* @param id
* @return
*/
public int deleteBook(int id) {
if(checkDb()) {
int result = db.delete(BookDBHelper.BOOK_TABLE, BookDBHelper.BOOK_ID + "=?", new String[]{id + ""});
return result;
}
return -1;
}
/**
* 删除
* @param book
* @return
*/
public int deleteBook(Book book) {
if(book != null) {
deleteBook(book.getId());
}
return -1;
}
/**
* 更新
* @param book
* @return
*/
public int updateBook(Book book) {
if(book != null) {
if(checkDb()) {
ContentValues values = new ContentValues();
values.put(BookDBHelper.BOOK_NAME, book.getName());
values.put(BookDBHelper.BOOK_PRICE, book.getPrice());
values.put(BookDBHelper.BOOK_CAN_SALE, book.isCanSale());
return db.update(BookDBHelper.BOOK_TABLE, values,
BookDBHelper.BOOK_ID + "=?", new String[]{book.getId() + ""});
}
}
return -1;
}
/**
* 根据ID查找
* @param id
* @return
*/
public Book getBook(int id) {
if(checkDb()) {
Cursor cursor = db.query(BookDBHelper.BOOK_TABLE,
null, BookDBHelper.BOOK_ID + "=?", new String[]{id + ""}, null, null, null);
Book book = null;
if(cursor != null && cursor.moveToFirst()) {
book = new Book();
book.setId(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_ID)));
book.setName(cursor.getString(cursor.getColumnIndex(BookDBHelper.BOOK_NAME)));
book.setPrice(cursor.getFloat(cursor.getColumnIndex(BookDBHelper.BOOK_PRICE)));
book.setCanSale(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_CAN_SALE))
== 1 ? true : false);
}
cursor.close();
return book;
}
return null;
}
/**
* 查找全部
* @return
*/
public List<Book> getAllBooks() {
if(checkDb()) {
List<Book> books = new ArrayList<Book>();
Cursor cursor = db.query(BookDBHelper.BOOK_TABLE, null, null, null, null, null, null);
if(cursor != null) {
while(cursor.moveToNext()) {
Book book = new Book();
book.setId(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_ID)));
book.setName(cursor.getString(cursor.getColumnIndex(BookDBHelper.BOOK_NAME)));
book.setPrice(cursor.getFloat(cursor.getColumnIndex(BookDBHelper.BOOK_PRICE)));
book.setCanSale(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_CAN_SALE))
== 1 ? true : false);
books.add(book);
}
}
cursor.close();
return books;
}
return null;
}
}
最后是使用的代码，以查为例：
[java]
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BookDao bookDao = new BookDao(activity);
bookDao.open();
Book book = bookDao.getBook(1);
bookDao.close();
下面是Demo运行的截图：
最后是Demo的源码：
http://download.csdn.net/detail/shinay/4533586
Android的数据库是用Sqlite3，关于增删改查的语句，其实与别的数据是区别并的大，网上也有很多，所以就不说这个问题。
这次主要是写写我在项目中用到数据库编码习惯。
以增删改查Book为例，先是结构：
跟着看Book类：
[java]
view plain
copy
print?
package com.lxb.dbdemo.model;
public class Book {
private int id; // ID
private String name; // 名称
private float price; // 价格
private boolean canSale; // 是否可售
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public boolean isCanSale() {
return canSale;
}
public void setCanSale(boolean canSale) {
this.canSale = canSale;
}
@Override
public String toString() {
return "Book [id=" + id + ", name=" + name + ", price=" + price
+ ", canSale=" + canSale + "]";
}
}
package com.lxb.dbdemo.model;
public class Book {
private int id; // ID
private String name; // 名称
private float price; // 价格
private boolean canSale; // 是否可售
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public boolean isCanSale() {
return canSale;
}
public void setCanSale(boolean canSale) {
this.canSale = canSale;
}
@Override
public String toString() {
return "Book [id=" + id + ", name=" + name + ", price=" + price
+ ", canSale=" + canSale + "]";
}
}然后是比较重要的继承自SQLiteOpenHelper的类，这里主要是建表及升级数据库操作（升级数据库只要把数据库版本号往上提就行）：
[java]
view plain
copy
print?
package com.lxb.dbdemo.db;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class BookDBHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "book_db"; // 数据库名称
private static final int DATABASE_VERSION = 1; // 数据库版本
public static final String BOOK_TABLE = "book_table"; // 书表名
public static final String BOOK_ID = "book_id"; // 书ID
public static final String BOOK_NAME = "book_name"; // 书名
public static final String BOOK_PRICE = "book_price"; // 书价格
public static final String BOOK_CAN_SALE = "book_cansale"; // 是否可售
public BookDBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// 建表操作
StringBuilder sb = new StringBuilder();
sb.append("CREATE TABLE IF NOT EXISTS " + BOOK_TABLE + "(");
sb.append(BOOK_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,");
sb.append(BOOK_NAME + " VARCHAR(100),");
sb.append(BOOK_PRICE + " VARCHAR(100),");
sb.append(BOOK_CAN_SALE + " INTEGER)");
db.execSQL(sb.toString());
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + BOOK_TABLE);
onCreate(db);
}
}
package com.lxb.dbdemo.db;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class BookDBHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "book_db"; // 数据库名称
private static final int DATABASE_VERSION = 1; // 数据库版本
public static final String BOOK_TABLE = "book_table"; // 书表名
public static final String BOOK_ID = "book_id"; // 书ID
public static final String BOOK_NAME = "book_name"; // 书名
public static final String BOOK_PRICE = "book_price"; // 书价格
public static final String BOOK_CAN_SALE = "book_cansale"; // 是否可售
public BookDBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// 建表操作
StringBuilder sb = new StringBuilder();
sb.append("CREATE TABLE IF NOT EXISTS " + BOOK_TABLE + "(");
sb.append(BOOK_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,");
sb.append(BOOK_NAME + " VARCHAR(100),");
sb.append(BOOK_PRICE + " VARCHAR(100),");
sb.append(BOOK_CAN_SALE + " INTEGER)");
db.execSQL(sb.toString());
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + BOOK_TABLE);
onCreate(db);
}
}接下来是一个Dao类，实现了增删改查的方法等：
[java]
view plain
copy
print?
package com.lxb.dbdemo.db.dao;
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.lxb.dbdemo.db.BookDBHelper;
import com.lxb.dbdemo.model.Book;
public class BookDao {
private BookDBHelper helper;
private SQLiteDatabase db; // 数据库对象
public BookDao(Context context) {
helper = new BookDBHelper(context);
}
/**
* 打开数据库
*/
public void open() {
if(db == null || !db.isOpen()) {
db = helper.getWritableDatabase();
}
}
/**
* 关闭数据库
*/
public void close() {
db.close();
db = null;
}
/**
* 检查数据库是否可用
* @return
*/
private boolean checkDb() {
open();
if(db != null && db.isOpen()) {
return true;
}
return false;
}
/**
* 保存
* @param book
* @return
*/
public int saveBook(Book book) {
ContentValues values = new ContentValues();
values.put(BookDBHelper.BOOK_NAME, book.getName());
values.put(BookDBHelper.BOOK_PRICE, book.getPrice());
values.put(BookDBHelper.BOOK_CAN_SALE, book.isCanSale());
if(checkDb()) {
long id = db.insert(BookDBHelper.BOOK_TABLE, BookDBHelper.BOOK_ID, values);
return Integer.parseInt(id + "");
}
return -1;
}
/**
* 根据ID删除
* @param id
* @return
*/
public int deleteBook(int id) {
if(checkDb()) {
int result = db.delete(BookDBHelper.BOOK_TABLE, BookDBHelper.BOOK_ID + "=?", new String[]{id + ""});
return result;
}
return -1;
}
/**
* 删除
* @param book
* @return
*/
public int deleteBook(Book book) {
if(book != null) {
deleteBook(book.getId());
}
return -1;
}
/**
* 更新
* @param book
* @return
*/
public int updateBook(Book book) {
if(book != null) {
if(checkDb()) {
ContentValues values = new ContentValues();
values.put(BookDBHelper.BOOK_NAME, book.getName());
values.put(BookDBHelper.BOOK_PRICE, book.getPrice());
values.put(BookDBHelper.BOOK_CAN_SALE, book.isCanSale());
return db.update(BookDBHelper.BOOK_TABLE, values,
BookDBHelper.BOOK_ID + "=?", new String[]{book.getId() + ""});
}
}
return -1;
}
/**
* 根据ID查找
* @param id
* @return
*/
public Book getBook(int id) {
if(checkDb()) {
Cursor cursor = db.query(BookDBHelper.BOOK_TABLE,
null, BookDBHelper.BOOK_ID + "=?", new String[]{id + ""}, null, null, null);
Book book = null;
if(cursor != null && cursor.moveToFirst()) {
book = new Book();
book.setId(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_ID)));
book.setName(cursor.getString(cursor.getColumnIndex(BookDBHelper.BOOK_NAME)));
book.setPrice(cursor.getFloat(cursor.getColumnIndex(BookDBHelper.BOOK_PRICE)));
book.setCanSale(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_CAN_SALE))
== 1 ? true : false);
}
cursor.close();
return book;
}
return null;
}
/**
* 查找全部
* @return
*/
public List<Book> getAllBooks() {
if(checkDb()) {
List<Book> books = new ArrayList<Book>();
Cursor cursor = db.query(BookDBHelper.BOOK_TABLE, null, null, null, null, null, null);
if(cursor != null) {
while(cursor.moveToNext()) {
Book book = new Book();
book.setId(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_ID)));
book.setName(cursor.getString(cursor.getColumnIndex(BookDBHelper.BOOK_NAME)));
book.setPrice(cursor.getFloat(cursor.getColumnIndex(BookDBHelper.BOOK_PRICE)));
book.setCanSale(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_CAN_SALE))
== 1 ? true : false);
books.add(book);
}
}
cursor.close();
return books;
}
return null;
}
}
package com.lxb.dbdemo.db.dao;
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.lxb.dbdemo.db.BookDBHelper;
import com.lxb.dbdemo.model.Book;
public class BookDao {
private BookDBHelper helper;
private SQLiteDatabase db; // 数据库对象
public BookDao(Context context) {
helper = new BookDBHelper(context);
}
/**
* 打开数据库
*/
public void open() {
if(db == null || !db.isOpen()) {
db = helper.getWritableDatabase();
}
}
/**
* 关闭数据库
*/
public void close() {
db.close();
db = null;
}
/**
* 检查数据库是否可用
* @return
*/
private boolean checkDb() {
open();
if(db != null && db.isOpen()) {
return true;
}
return false;
}
/**
* 保存
* @param book
* @return
*/
public int saveBook(Book book) {
ContentValues values = new ContentValues();
values.put(BookDBHelper.BOOK_NAME, book.getName());
values.put(BookDBHelper.BOOK_PRICE, book.getPrice());
values.put(BookDBHelper.BOOK_CAN_SALE, book.isCanSale());
if(checkDb()) {
long id = db.insert(BookDBHelper.BOOK_TABLE, BookDBHelper.BOOK_ID, values);
return Integer.parseInt(id + "");
}
return -1;
}
/**
* 根据ID删除
* @param id
* @return
*/
public int deleteBook(int id) {
if(checkDb()) {
int result = db.delete(BookDBHelper.BOOK_TABLE, BookDBHelper.BOOK_ID + "=?", new String[]{id + ""});
return result;
}
return -1;
}
/**
* 删除
* @param book
* @return
*/
public int deleteBook(Book book) {
if(book != null) {
deleteBook(book.getId());
}
return -1;
}
/**
* 更新
* @param book
* @return
*/
public int updateBook(Book book) {
if(book != null) {
if(checkDb()) {
ContentValues values = new ContentValues();
values.put(BookDBHelper.BOOK_NAME, book.getName());
values.put(BookDBHelper.BOOK_PRICE, book.getPrice());
values.put(BookDBHelper.BOOK_CAN_SALE, book.isCanSale());
return db.update(BookDBHelper.BOOK_TABLE, values,
BookDBHelper.BOOK_ID + "=?", new String[]{book.getId() + ""});
}
}
return -1;
}
/**
* 根据ID查找
* @param id
* @return
*/
public Book getBook(int id) {
if(checkDb()) {
Cursor cursor = db.query(BookDBHelper.BOOK_TABLE,
null, BookDBHelper.BOOK_ID + "=?", new String[]{id + ""}, null, null, null);
Book book = null;
if(cursor != null && cursor.moveToFirst()) {
book = new Book();
book.setId(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_ID)));
book.setName(cursor.getString(cursor.getColumnIndex(BookDBHelper.BOOK_NAME)));
book.setPrice(cursor.getFloat(cursor.getColumnIndex(BookDBHelper.BOOK_PRICE)));
book.setCanSale(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_CAN_SALE))
== 1 ? true : false);
}
cursor.close();
return book;
}
return null;
}
/**
* 查找全部
* @return
*/
public List<Book> getAllBooks() {
if(checkDb()) {
List<Book> books = new ArrayList<Book>();
Cursor cursor = db.query(BookDBHelper.BOOK_TABLE, null, null, null, null, null, null);
if(cursor != null) {
while(cursor.moveToNext()) {
Book book = new Book();
book.setId(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_ID)));
book.setName(cursor.getString(cursor.getColumnIndex(BookDBHelper.BOOK_NAME)));
book.setPrice(cursor.getFloat(cursor.getColumnIndex(BookDBHelper.BOOK_PRICE)));
book.setCanSale(cursor.getInt(cursor.getColumnIndex(BookDBHelper.BOOK_CAN_SALE))
== 1 ? true : false);
books.add(book);
}
}
cursor.close();
return books;
}
return null;
}
}最后是使用的代码，以查为例：
[java]
view plain
copy
print?
BookDao bookDao = new BookDao(activity);
bookDao.open();
Book book = bookDao.getBook(1);
bookDao.close();
BookDao bookDao = new BookDao(activity); bookDao.open(); Book book = bookDao.getBook(1); bookDao.close();
下面是Demo运行的截图：
最后是Demo的源码：
http://download.csdn.net/detail/shinay/4533586
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