Android打開外部DB文件

DB文件要放在Assets文件夾下，封裝一個工具類，以下：

  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幫助類：打開外部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      * 數據庫名字
 24      */
 25     public static String DB_NAME = "ExternalDB.db";
 26     /**
 27      * 內存DB文件存儲路徑
 28      */
 29     public static String DB_PATH = "";
 30     private static int BUFFER_SIZE = 40000;
 31 
 32     /**
 33      * 單例模式：獲取DBManager實例
 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      * 獲取數據庫
 52      * 
 53      * @return
 54      */
 55     public SQLiteDatabase getDatabase() {
 56         return mDatabase;
 57     }
 58 
 59     /**
 60      * 設置數據庫
 61      * 
 62      * @param db
 63      */
 64     public void setDatabase(SQLiteDatabase db) {
 65         mDatabase = db;
 66     }
 67 
 68     /**
 69      * 關閉數據庫
 70      */
 71     public void closeDatabase() {
 72         if (mDatabase != null) {
 73             mDatabase.close();
 74         }
 75     }
 76 
 77     /**
 78      * 從本地讀取DB文件 ，並加載到內存
 79      * 
 80      * @param dB_PATH
 81      * @return
 82      */
 83     private static SQLiteDatabase openDatabase() {
 84         try {
 85             File file = new File(DB_PATH);
 86             // 若是內存中不存在，則開始導入
 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 }