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iPhone Cool Projects phần 9

kiểm soát phát lại âm thanh và báo cáo tình trạng phát lại. AudioPlayer điều phối việc chuyển giao các dữ liệu thô âm thanh từ AudioFileRequest thành các gói AudioFileStream, sau đó vào AudioQueue bộ đệm, và cuối cùng là vào các phần cứng âm thanh. Làm thế nào quá trình này hoạt động sẽ trở nên rõ ràng khi chúng ta nhìn vào mã | 164 CHAPTER 7 Going the Routesy Way with Core Location XML and SQLite 7-5. Selecting frameworks and libraries to link to the project Let s take a moment to become familiar with the libraries and frameworks that we just linked to the project CoreLocation.framework This framework provides us with access to the iPhone s location API which your application uses to help the user find the nearest BART station. SystemConfiguration.framework This contains APIs that allow us to determine the configuration of the user s device. In the case of Routesy we need to make sure the network is available before attempting to retrieve prediction data. libsqlite3.dylib This dynamic C library provides an API for querying the static SQL database included with our project. CHAPTER 7 Going the Routesy Way with Core Location XML andSQLite 165 I libxml2.dylib This dynamic library gives the application access to fast parsing of XML documents and support for XPath querying which will help us quickly find the prediction data the user requests. 6. The libxml2 library also requires that you include a reference to the libxml header files which are located on your system in the path usr include libxml2. To add the headers select the Build tab in the Target Info window that we ve already opened and add the path to the Header Search Paths field as shown in Figure 7-6. 7-6. Adding the libxml2 header search paths to the build settings Invoke the dialog shown in Figure 7-6 by double-clicking the Header Search Paths field. Make sure that you check the Recursive box so that your application can find all of the libxml2 headers that you ll need to build your application. Now that all of your project dependencies have been set up we re ready to get started coding. First we need to build the model for your project the objects that will represent pieces of data. For Routesy there are two types of objects a station and a prediction. You ll start by creating an object for each. 166 CHAPTER 7 Going the Routesy .