Android项目中单实例数据库类,解决database is locked

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;

 }

}