Chương này giải thích các khái niệm chính đằng sau xem. Bạn tìm hiểu về quan điểm hình học tại Mục . Trong Phần , chúng tôi bao gồm các chủ đề của hệ thống cấp bậc xem. Mục, tiếp theo 5,3 thảo luận, rất chi tiết, giao diện cảm ứng đa điểm. Trong phần này, bạn tìm hiểu làm thế nào để nhận biết cử chỉ cảm ứng đa điểm. | 5 The View This chapter explains the main concepts behind views. You learn about view geometry in Section . In Section we cover the topic of view hierarchy. Next Section discusses in great detail the multitouch interface. In this section you learn how to recognize multitouch gestures. After that we discuss several animation techniques in Section . Next Section deals with how to use Quartz 2D functions for drawing inside a view. Finally we summarize the chapter in Section . View Geometry This section covers the three geometric properties of the uiview class that you need to understand frame bounds and center. Before explaining these properties let s first look at some of the structures and functions used in specifying their values. Useful geometric type definitions The following types are used throughout the text CGFioat represents a floating point number and is defined as typedef float CGFloat CGPoint is a structure that represents a geometric point. It is defined as struct CGPoint CGFloat x CGFloat y typedef struct CGPoint CGPoint The x value represents the x-coordinate of the point and the y value represents its y-coordinate. 116 iPhone SDK 3 Programming You will use CGPoint a lot. CGPointMake is a convenient function defined to make a CGPoint from a pair of x and y values and is defined as follows CGPoint CGPointMake CGFloat x CGFloat y CGSize is a structure used to represent width and height values. It is declared as follows struct CGSize CGFloat width CGFloat height typedef struct CGSize CGSize where width is the width value and height is the height value. To make a CGSize structure from a width and a height use the utility function CGSizeMake declared as follows CGSize CGSizeMake CGFloat width CGFloat height CGRect is used to represent the location and dimensions of a rectangle. It is declared as follows struct CGRect CGPoint origin CGSize size typedef struct CGRect CGRect The origin value represents the upper-left point of the
