Đang chuẩn bị liên kết để tải về tài liệu:
Programming the Be Operating System-Chapter 4: Windows, Views, and Messages

Tham khảo tài liệu 'programming the be operating system-chapter 4: windows, views, and messages', công nghệ thông tin, hệ điều hành phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 4 In this chapter Windows Views Messaging Windows Views and Messages A window serves as a program s means of communicating with the user. In order to provide information to a user a window needs to be able to draw either text or graphics. And in order to receive information from a user a window needs to be aware of user actions such as mouse button clicks or key presses. Views make both these modes of communication possible. All drawing takes place in views. And views are recipients of messages that are transmitted from the Application Server to the program in response to user actions. All three of these topics windows views and messages can be discussed individually and this chapter does just that. To be of real use though the interaction of these topics must be described this chapter of course does that as well. Windows Your program s windows will be objects of a class or classes that your project derives from the BWindow class. The BWindow class is one of many classes in the Interface Kit the largest of the Be kits. Most other Interface Kit class objects draw to a window so they expect a BWindow object to exist they work in conjunction with the window object. Because it is a type of BLooper a BWindow object runs in its own thread and runs its own message loop. This loop is used to receive and respond to messages from the Application Server. In this chapter s Messaging section you ll see how a window often delegates the handling of a message to one of the views present in the window. The ever-present interaction of windows views and messages accounts for the combining of these three topics in this chapter. 98 Windows 99 Window Characteristics A window s characteristics its size screen location and peripheral elements close button zoom button and so forth are all established in the constructor of the BWindow-derived class of the window. BWindow constructor A typical BWindow-derived class constructor is often empty MyHelloWindow MyHelloWindow BRect frame BWindow .