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：

  1 package com.XX.DB;

  2 

  3 import java.io.File;

  4 import java.io.FileOutputStream;

  5 import java.io.IOException;

  6 import java.io.InputStream;

  7 

  8 import android.content.Context;

  9 import android.content.res.AssetManager;

 10 import android.database.sqlite.SQLiteDatabase;

 11 import android.os.Environment;

 12 

 13 /**

 14  * SQLite帮助类：打开外部DB文件

 15  * 

 16  * @author XX

 17  * @since 2015年7月8日 11:20:28

 18  */

 19 public class DBManager {

 20     public static SQLiteDatabase mDatabase = null;

 21     private static Context mContext;

 22     /**

 23      * 数据库名字

 24      */

 25     public static String DB_NAME = "ExternalDB.db";

 26     /**

 27      * 内存DB文件存储路径

 28      */

 29     public static String DB_PATH = "";

 30     private static int BUFFER_SIZE = 40000;

 31 

 32     /**

 33      * 单例模式：获取DBManager实例

 34      * 

 35      * @param context

 36      * @return

 37      */

 38     public static SQLiteDatabase getInstance(Context context) {

 39         mContext = context;

 40         DB_PATH = "/data" + Environment.getDataDirectory().getAbsolutePath()

 41                 + "/" + mContext.getPackageName() + "/databases";

 42         if (mDatabase == null) {

 43             synchronized (DBManager.class) {

 44                 mDatabase = openDatabase();

 45             }

 46         }

 47         return mDatabase;

 48     }

 49 

 50     /**

 51      * 获取数据库

 52      * 

 53      * @return

 54      */

 55     public SQLiteDatabase getDatabase() {

 56         return mDatabase;

 57     }

 58 

 59     /**

 60      * 设置数据库

 61      * 

 62      * @param db

 63      */

 64     public void setDatabase(SQLiteDatabase db) {

 65         mDatabase = db;

 66     }

 67 

 68     /**

 69      * 关闭数据库

 70      */

 71     public void closeDatabase() {

 72         if (mDatabase != null) {

 73             mDatabase.close();

 74         }

 75     }

 76 

 77     /**

 78      * 从本地读取DB文件 ，并加载到内存

 79      * 

 80      * @param dB_PATH

 81      * @return

 82      */

 83     private static SQLiteDatabase openDatabase() {

 84         try {

 85             File file = new File(DB_PATH);

 86             // 如果内存中不存在，则开始导入

 87             if (!file.exists()) {

 88                 file.mkdirs();

 89                 AssetManager manager = mContext.getAssets();

 90                 InputStream is = manager.open(DB_NAME);

 91                 FileOutputStream fos = new FileOutputStream(DB_PATH + "/"

 92                         + DB_NAME);

 93                 byte[] buffer = new byte[BUFFER_SIZE];

 94                 int count = 0;

 95                 while ((count = is.read(buffer)) > 0) {

 96                     fos.write(buffer, 0, count);

 97                 }

 98                 fos.close();

 99                 is.close();

100             }

101             SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(DB_PATH

102                     + "/" + DB_NAME, null);

103             return db;

104         } catch (IOException e) {

105             e.printStackTrace();

106         }

107         return null;

108     }

109 }