iOS sqlite 写失败 返回SQLITE_BUSY

Cocos2d-x
#1

我在ios下面写sqlite3怎么都不行啊，一直都是返回SQLITE_BUSY。
刚开始我是因为没有把数据库文件copy到document路径下面，copy到document下之后，还是不能写。

- (BOOL) initializeDb
{
    NSLog (@"initializeDB");
    // look to see if DB is in known location (~/Documents/$DATABASE_FILE_NAME)
    //START:code.DatabaseShoppingList.findDocumentsDirectory
    NSArray *searchPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentFolderPath = ;
    //查看文件目录
    NSLog(@"%@",documentFolderPath);
    NSString* dbFilePath = ;
    
    std::string *dbPathStr = new std::string();
    Layout::sharedLayout()->setDBPath(*dbPathStr);
    
    //END:code.DatabaseShoppingList.findDocumentsDirectory
    ;
    //START:code.DatabaseShoppingList.copyDatabaseFileToDocuments
    if (!  fileExistsAtPath: dbFilePath])
    {
        // didn't find db, need to copy
        NSString *backupDbPath =  pathForResource:@"News" ofType:@"db3"];
        if (backupDbPath == nil)
        {
            // couldn't find backup db to copy, bail
            return NO;
        }
        else
        {
            BOOL copiedBackupDb =  copyItemAtPath:backupDbPath toPath:dbFilePath error:nil];
            if (! copiedBackupDb)
            {
                // copying backup db failed, bail
                return NO;
            }
        }
    }
    return YES;
    //END:code.DatabaseShoppingList.copyDatabaseFileToDocuments
    NSLog (@"bottom of initializeDb");
}

上面这段代码是app初始化的时候执行的。用一个全局的对象把得到的document的路径保存起来了，方便后面读写使用。

    const char* path = Layout::sharedLayout()->getDBPath().c_str();
    
	int iRet = 0;
	sqlite3 *db;
	iRet = sqlite3_open(path, &db);
	if(iRet != SQLITE_OK)
	{
		sqlite3_close(db);
		return;
	}
    sqlite3_stmt * stmt;
    CCString *stmtString = CCString::createWithFormat("UPDATE News SET Collect = %d WHERE ID = %d", m_isCollected,m_newsID);
	sqlite3_prepare_v2(db,stmtString->getCString(),-1,&stmt,NULL);

    iRet = sqlite3_step(stmt);
    
    sqlite3_finalize(stmt);
	sqlite3_close(db);

这段代码是在后面update数据的。

在模拟器上和真机上都试过了，都不能写入数据库，得到的结果都是SQLITE_BUSY.
请问这是什么原因呢？