Android打开外部DB文件

DB文件要放在Assets文件夹下，封装一个工具类，如下：

 package com.XX.DB;

 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;

 import android.content.Context;
 import android.content.res.AssetManager;
 import android.database.sqlite.SQLiteDatabase;
 import android.os.Environment;

 /**
  * SQLite帮助类：打开外部DB文件
  *
  * @author XX
  * @since 2015年7月8日 11:20:28
  */
 public class DBManager {
     public static SQLiteDatabase mDatabase = null;
     private static Context mContext;
     /**
      * 数据库名字
      */
     public static String DB_NAME = "ExternalDB.db";
     /**
      * 内存DB文件存储路径
      */
     public static String DB_PATH = "";
     private static int BUFFER_SIZE = 40000;

     /**
      * 单例模式：获取DBManager实例
      *
      * @param context
      * @return
      */
     public static SQLiteDatabase getInstance(Context context) {
         mContext = context;
         DB_PATH = "/data" + Environment.getDataDirectory().getAbsolutePath()
                 + "/" + mContext.getPackageName() + "/databases";
         if (mDatabase == null) {
             synchronized (DBManager.class) {
                 mDatabase = openDatabase();
             }
         }
         return mDatabase;
     }

     /**
      * 获取数据库
      *
      * @return
      */
     public SQLiteDatabase getDatabase() {
         return mDatabase;
     }

     /**
      * 设置数据库
      *
      * @param db
      */
     public void setDatabase(SQLiteDatabase db) {
         mDatabase = db;
     }

     /**
      * 关闭数据库
      */
     public void closeDatabase() {
         if (mDatabase != null) {
             mDatabase.close();
         }
     }

     /**
      * 从本地读取DB文件 ，并加载到内存
      *
      * @param dB_PATH
      * @return
      */
     private static SQLiteDatabase openDatabase() {
         try {
             File file = new File(DB_PATH);
             // 如果内存中不存在，则开始导入
             if (!file.exists()) {
                 file.mkdirs();
                 AssetManager manager = mContext.getAssets();
                 InputStream is = manager.open(DB_NAME);
                 FileOutputStream fos = new FileOutputStream(DB_PATH + "/"
                         + DB_NAME);
                 byte[] buffer = new byte[BUFFER_SIZE];
                 int count = 0;
                 while ((count = is.read(buffer)) > 0) {
                     fos.write(buffer, 0, count);
                 }
                 fos.close();
                 is.close();
             }
             SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(DB_PATH
                     + "/" + DB_NAME, null);
             return db;
         } catch (IOException e) {
             e.printStackTrace();
         }
         return null;
     }
 }