android项目中单实例数据库类

一、数据库操作

package com.ping.db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

/**
* @describe <数据库操作>
*/
public class SQLiteTool extends SQLiteOpenHelper {
private static final String DB_NAME = "medicalscience.db"; // 数据库文件名
private static final int VERSION = 1;// 数据库版本

public static SQLiteTool newInstance(Context context) {
return new SQLiteTool(context, DB_NAME, null, VERSION);
}

private SQLiteTool(Context context, String name, CursorFactory factory, int version) {
super(context, name, factory, version);
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(DBTCollect.createTableSQL());//有需要创建表时，可以在这添加
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {//当数据库版本变大时调用
onCreate(db);
}
}

二、数据库管理类

package com.ping.db;

import java.util.concurrent.atomic.AtomicInteger;

import android.annotation.SuppressLint;
import android.database.sqlite.SQLiteDatabase;
import android.os.Build;

import com.ping.MyApplication;

/**
* @describe <数据库管理类>
*/
public class DBManager {
private AtomicInteger dbOpenCount = new AtomicInteger();//计数器
private static DBManager instance;
private static SQLiteTool sqlLiteTool;
private SQLiteDatabase database;

public static synchronized DBManager getInstance() {
if (instance == null) {
synchronized (DBManager.class) {
if (instance == null) {
instance = new DBManager();
}
}
}
return instance;
}

private DBManager() {
sqlLiteTool = SQLiteTool.newInstance(MyApplication.getInstance().getApplicationContext());
}

@SuppressLint("NewApi")
public synchronized SQLiteDatabase openDatabase() {
if (dbOpenCount.incrementAndGet() == 1) {
database = sqlLiteTool.getWritableDatabase();
if (Build.VERSION.SDK_INT >= 11) {
database.enableWriteAheadLogging();// 允许读写同时进行
}
}
return database;
}

public synchronized void closeDatabase() {
if (dbOpenCount.decrementAndGet() == 0) {
database.close();
database = null;
}
}
}

三、数据增删改查

package com.ping.db;

import java.util.ArrayList;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

/**
* @describe <数据库操作--收藏表的操作 >
*/
public class DBTCollect {
public static final String TNAME = "Tcollect";

// 创建表的语句
public static String createTableSQL() {
return "CREATE TABLE IF NOT EXISTS " + TNAME + " (kid INTEGER PRIMARY KEY AUTOINCREMENT, id TEXT, title TEXT)";
}

// 删除表的语句
public static String deleteTabelSQL() {
return "DROP TABLE IF EXISTS " + TNAME;
}

//查询数据是否存在
public static boolean isCollected(String id) {
boolean isCollected = false;
SQLiteDatabase db = DBManager.getInstance().openDatabase();//获得SQLiteDatabase对象
String sql = "select * from " + TNAME + " where id = '" + id + "'";
Cursor cursor = db.rawQuery(sql, null);
if (cursor.getCount() > 0) {
isCollected = true;
}
cursor.close();
DBManager.getInstance().closeDatabase();//关闭
return isCollected;
}

// 删除数据
public static void deleteCollect(String mid) {
SQLiteDatabase db = DBManager.getInstance().openDatabase();
db.delete(TNAME, "id = ?", new String[] { id });
DBManager.getInstance().closeDatabase();
}

//增加数据
public static void addCollect(Object obj) {
SQLiteDatabase db = DBManager.getInstance().openDatabase();
ContentValues cv = new ContentValues();
cv.put("id", obj.id);
cv.put("title", obj.title);
db.insert(TNAME, null, cv);
DBManager.getInstance().closeDatabase();
}

//查询数据
public static ArrayList<Object> getAllCollect() {
SQLiteDatabase db = DBManager.getInstance().openDatabase();
Cursor cursor = db.query(TNAME, null, null, null, null, null, null);
ArrayList<Object> objs = new ArrayList<Object>();
while (cursor.moveToNext()) {
Object obj = new Object();
obj.id = cursor.getString(cursor.getColumnIndex("id"));
obj.title = cursor.getString(cursor.getColumnIndex("title"));
objs.add(obj);
}
cursor.close();
DBManager.getInstance().closeDatabase();
return objs;
}
}

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