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iPhone Design Award-Winning Projects phần 5

Không chỉ phát triển thời gian nhỏ sẽ có thể truy cập vào mạng của Ngmoco điểm, thách thức và playability, họ cũng sẽ có thể sử dụng số liệu của công ty và các chương trình khuyến mãi động cơ. Tuy nhiên, xây dựng mạng lưới + Ngoài ra có nguy cơ đáng kể. Đã, hàng triệu người đã trả tiền cho các trò chơi | 72 CHAPTER 5 AccuTerra was to have the app check for outstanding transactions with Apple. If it s something that the user pauses or cancels themselves our app considers itself done with the transaction Barnhart explains. That said the user can come back anytime and query our servers and see that yes they have this product installed and they can go ahead and download it for free again without having to go through any kind of iTunes transaction. Of course it s not always that easy says Witonsky. There s a stumbling block with the way they ve set up their StoreKit framework that can create problems for users who are resetting their phones or are trying to transfer data over to new phones he explains. It s not a big scenario but it s a complication. When purchase information is stored in two places it s harder to make it clear to the user what s happening and how they can get their data back. Figure 5-6. Each map in AccuTerra s store shows you the area of coverage you re buying. This one is of Deschutes River State Recreation Area in Oregon. PVRTC or Broke In Chapter 3 we discussed using PVRTC to compress images economically. For AccuTerra PVRTC was not only a nice way to cut down on memory-hogging it was the difference between a usable app and an unusable one. Because we use PVRTC we CHAPTER 5 AccuTerra 73 can fit a number of tiles in memory and therefore the user experience of panning and zooming is much better because the app doesn t have to go outside the data structure and bring back more tiles Witonsky explains. But there are always limitations because the app can t possibly load all the tiles from a given stack it has to decide which ones take priority. We developed sophisticated algorithms to manage that which tiles get loaded he says. Barnhart says the algorithm essentially tries to predict what area of the map the user will want to see next and load it in memory. The algorithm does a lookup based on the screen location reference and finds the appropriate map