实现iPhone电子书的分页显示功能

1 // Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
2 - (void)viewDidLoad {
3 [super viewDidLoad];
4
5 //
6 totalPages &＃61; 0;
7 currentPage &＃61; 0;
8
9 //
10 textLabel.numberOfLines &＃61; 0;
11
12 //
13 if (!text) {
14 // 从文件里加载文本串
15 [self loadString];
16
17 // 计算文本串的大小尺寸
18 CGSize totalTextSize &＃61; [text sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE_MAX]
19 constrainedToSize:CGSizeMake(textLabel.frame.size.width, CGFLOAT_MAX)
20 lineBreakMode:UILineBreakModeWordWrap];
21
22 // 如果一页就能显示完&＃xff0c;直接显示所有文本串即可。
23 if (totalTextSize.height 24 textLabel.text &＃61; text;
25 }
26 else {
27 // 计算理想状态下的页面数量和每页所显示的字符数量&＃xff0c;只是拿来作为参考值用而已&＃xff01;
28 NSUInteger textLength &＃61; [text length];
29 referTotalPages &＃61; (int)totalTextSize.height/(int)textLabel.frame.size.height&＃43;1;
30 referCharatersPerPage &＃61; textLength/referTotalPages;
31
32 // 申请最终保存页面NSRange信息的数组缓冲区
33 int maxPages &＃61; referTotalPages;
34 rangeOfPages &＃61; (NSRange *)malloc(referTotalPages*sizeof(NSRange));
35 memset(rangeOfPages, 0x0, referTotalPages*sizeof(NSRange));
36
37 // 页面索引
38 int page &＃61; 0;
39
40 for (NSUInteger location &＃61; 0; location 41 // 先计算临界点&＃xff08;尺寸刚刚超过UILabel尺寸时的文本串&＃xff09;
42 NSRange range &＃61; NSMakeRange(location, referCharatersPerPage);
43
44 // reach end of text ?
45 NSString *pageText;
46 CGSize pageTextSize;
47
48 while (range.location &＃43; range.length 49 pageText &＃61; [text substringWithRange:range];
50
51 pageTextSize &＃61; [pageText sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE_MAX]
52 constrainedToSize:CGSizeMake(textLabel.frame.size.width, CGFLOAT_MAX)
53 lineBreakMode:UILineBreakModeWordWrap];
54
55 if (pageTextSize.height > textLabel.frame.size.height) {
56 break;
57 }
58 else {
59 range.length &＃43;&＃61; referCharatersPerPage;
60 }
61 }
62
63 if (range.location &＃43; range.length >&＃61; textLength) {
64 range.length &＃61; textLength - range.location;
65 }
66
67 // 然后一个个缩短字符串的长度&＃xff0c;当缩短后的字符串尺寸小于textLabel的尺寸时即为满足
68 while (range.length > 0) {
69 pageText &＃61; [text substringWithRange:range];
70
71 pageTextSize &＃61; [pageText sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE_MAX]
72 constrainedToSize:CGSizeMake(textLabel.frame.size.width, CGFLOAT_MAX)
73 lineBreakMode:UILineBreakModeWordWrap];
74
75 if (pageTextSize.height <&＃61; textLabel.frame.size.height) {
76 range.length &＃61; [pageText length];
77 break;
78 }
79 else {
80 range.length -&＃61; 2;
81 }
82 }
83
84 // 得到一个页面的显示范围
85 if (page >&＃61; maxPages) {
86 maxPages &＃43;&＃61; 10;
87 rangeOfPages &＃61; (NSRange *)realloc(rangeOfPages, maxPages*sizeof(NSRange));
88 }
89 rangeOfPages[page&＃43;&＃43;] &＃61; range;
90
91 // 更新游标
92 location &＃43;&＃61; range.length;
93 }
94
95 // 获取最终页面数量
96 totalPages &＃61; page;
97
98 // 更新UILabel内容
99 textLabel.text &＃61; [text substringWithRange:rangeOfPages[currentPage]];
100 }
101 }
102
103 // 显示当前页面进度信息&＃xff0c;格式为&＃xff1a;"8/100"
104 pageInfoLabel.text &＃61; [NSString stringWithFormat:&＃64;"%d/%d", currentPage&＃43;1, totalPages];
105 }

1 // 上一页
2 - (IBAction)actionPrevious:(id)sender {
3 if (currentPage > 0) {
4 currentPage--;
5
6 NSRange range &＃61; rangeOfPages[currentPage];
7 NSString *pageText &＃61; [text substringWithRange:range];
8
9 textLabel.text &＃61; pageText;
10
11 //
12 pageInfoLabel.text &＃61; [NSString stringWithFormat:&＃64;"%d/%d", currentPage&＃43;1, totalPages];
13 }
14 }

1 // 下一页
2 - (IBAction)actionNext:(id)sender {
3 if (currentPage 1) {
4 currentPage&＃43;&＃43;;
5
6 NSRange range &＃61; rangeOfPages[currentPage];
7 NSString *pageText &＃61; [text substringWithRange:range];
8
9 textLabel.text &＃61; pageText;
10
11 //
12 pageInfoLabel.text &＃61; [NSString stringWithFormat:&＃64;"%d/%d", currentPage&＃43;1, totalPages];
13 }
14 }