Android操作存放在assets文件夹下SQLite数据库的方法

package com.sin.android.database; 
import java.io.File; 
import java.io.FileOutputStream; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.util.HashMap; 
import java.util.Map; 
import android.content.Context; 
import android.content.SharedPreferences; 
import android.content.res.AssetManager; 
import android.database.sqlite.SQLiteDatabase; 
import android.util.Log; 
/** 
 * This is a Assets Database Manager 
 * Use it, you can use a assets database file in you application 
 * It will copy the database file to "/data/data/[your application package name]/database" when you first time you use it 
 * Then you can get a SQLiteDatabase object by the assets database file
 * @author RobinTang 
 * @time 2012-09-20 
 * 
 * 
 * How to use: 
 * 1. Initialize AssetsDatabaseManager 
 * 2. Get AssetsDatabaseManager 
 * 3. Get a SQLiteDatabase object through database file 
 * 4. Use this database object 
 * 
 * Using example: 
 * AssetsDatabaseManager.initManager(getApplication()); // this method is only need call one time 
 * AssetsDatabaseManager mg = AssetsDatabaseManager.getManager();  // get a AssetsDatabaseManager object 
 * SQLiteDatabase db1 = mg.getDatabase("db1.db");  // get SQLiteDatabase object, db1.db is a file in assets folder 
 * db1.??? // every operate by you want 
 * Of cause, you can use AssetsDatabaseManager.getManager().getDatabase("xx") to get a database when you need use a database 
 */ 
public class AssetsDatabaseManager { 
  private static String tag = "AssetsDatabase"; // for LogCat 
  private static String databasepath = "/data/data/%s/database"; // %s is packageName 
  // A mapping from assets database file to SQLiteDatabase object 
  private Map<String, SQLiteDatabase> databases = new HashMap<String, SQLiteDatabase>(); 
  // Context of application 
  private Context context = null; 
  // Singleton Pattern 
  private static AssetsDatabaseManager mInstance = null; 
  /** 
   * Initialize AssetsDatabaseManager 
   * @param context, context of application 
   */ 
  public static void initManager(Context context){ 
    if(mInstance == null){ 
      mInstance = new AssetsDatabaseManager(context); 
    } 
  } 
  /** 
   * Get a AssetsDatabaseManager object 
   * @return, if success return a AssetsDatabaseManager object, else return null 
   */ 
  public static AssetsDatabaseManager getManager(){ 
    return mInstance; 
  } 
  private AssetsDatabaseManager(Context context){ 
    this.context = context; 
  } 
  /** 
   * Get a assets database, if this database is opened this method is only return a copy of the opened database 
   * @param dbfile, the assets file which will be opened for a database 
   * @return, if success it return a SQLiteDatabase object else return null 
   */ 
  public SQLiteDatabase getDatabase(String dbfile) { 
    if(databases.get(dbfile) != null){ 
      Log.i(tag, String.format("Return a database copy of %s", dbfile)); 
      return (SQLiteDatabase) databases.get(dbfile); 
    } 
    if(context==null) 
      return null; 
    Log.i(tag, String.format("Create database %s", dbfile)); 
    String spath = getDatabaseFilepath(); 
    String sfile = getDatabaseFile(dbfile); 
    File file = new File(sfile); 
    SharedPreferences dbs = context.getSharedPreferences(AssetsDatabaseManager.class.toString(), 0); 
    boolean flag = dbs.getBoolean(dbfile, false); // Get Database file flag, if true means this database file was copied and valid
    if(!flag || !file.exists()){ 
      file = new File(spath); 
      if(!file.exists() && !file.mkdirs()){ 
        Log.i(tag, "Create \""+spath+"\" fail!"); 
        return null; 
      } 
      if(!copyAssetsToFilesystem(dbfile, sfile)){ 
        Log.i(tag, String.format("Copy %s to %s fail!", dbfile, sfile)); 
        return null; 
      } 
      dbs.edit().putBoolean(dbfile, true).commit(); 
    } 
    SQLiteDatabase db = SQLiteDatabase.openDatabase(sfile, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS); 
    if(db != null){ 
      databases.put(dbfile, db); 
    } 
    return db; 
  } 
  private String getDatabaseFilepath(){ 
    return String.format(databasepath, context.getApplicationInfo().packageName); 
  } 
  private String getDatabaseFile(String dbfile){ 
    return getDatabaseFilepath()+"/"+dbfile; 
  } 
  private boolean copyAssetsToFilesystem(String assetsSrc, String des){ 
    Log.i(tag, "Copy "+assetsSrc+" to "+des); 
    InputStream istream = null; 
    OutputStream ostream = null; 
    try{ 
      AssetManager am = context.getAssets(); 
      istream = am.open(assetsSrc); 
      ostream = new FileOutputStream(des); 
      byte[] buffer = new byte[1024]; 
      int length; 
      while ((length = istream.read(buffer))>0){ 
        ostream.write(buffer, 0, length); 
      } 
      istream.close(); 
      ostream.close(); 
    } 
    catch(Exception e){ 
      e.printStackTrace(); 
      try{ 
        if(istream!=null) 
          istream.close(); 
        if(ostream!=null) 
          ostream.close(); 
      } 
      catch(Exception ee){ 
        ee.printStackTrace(); 
      } 
      return false; 
    } 
    return true; 
  } 
  /** 
   * Close assets database 
   * @param dbfile, the assets file which will be closed soon 
   * @return, the status of this operating 
   */ 
  public boolean closeDatabase(String dbfile){ 
    if(databases.get(dbfile) != null){ 
      SQLiteDatabase db = (SQLiteDatabase) databases.get(dbfile);
      db.close(); 
      databases.remove(dbfile); 
      return true; 
    } 
    return false; 
  } 
  /** 
   * Close all assets database 
   */ 
  static public void closeAllDatabase(){ 
    Log.i(tag, "closeAllDatabase"); 
    if(mInstance != null){ 
      for(int i=0; i<mInstance.databases.size(); ++i){ 
        if(mInstance.databases.get(i)!=null){ 
          mInstance.databases.get(i).close(); 
        } 
      } 
      mInstance.databases.clear(); 
    } 
  } 
} 

// 初始化，只需要调用一次 
AssetsDatabaseManager.initManager(getApplication()); 
// 获取管理对象，因为数据库需要通过管理对象才能够获取 
AssetsDatabaseManager mg = AssetsDatabaseManager.getManager(); 
// 通过管理对象获取数据库 
SQLiteDatabase db1 = mg.getDatabase("db1.db"); 
// 对数据库进行操作 
db1.execSQL("insert into tb([ID],[content]) values(null, 'db1');");