Question

如何实现电子书的分页显示功能

Answer 1

经过几个小时的思考，终于有了解决方案，拿出来和大家分享，目前可以实现UILabel尺寸固定，
然后，根据文本内容和字体动态分页显示的效果。电子书方面的应用应该非常有用。

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
[super viewDidLoad];

//
totalPages = 0;
currentPage = 0;

//
textLabel.numberOfLines = 0;

//
if (!text) {
// 从文件里加载文本串
[self loadString];

// 计算文本串的大小尺寸
CGSize totalTextSize = [text sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE_MAX]
constrainedToSize:CGSizeMake(textLabel.frame.size.width, CGFLOAT_MAX)
lineBreakMode:UILineBreakModeWordWrap];

// 如果一页就能显示完，直接显示所有文本串即可。
if (totalTextSize.height < textLabel.frame.size.height) {
textLabel.text = text;
}
else {
// 计算理想状态下的页面数量和每页所显示的字符数量，只是拿来作为参考值用而已！
NSUInteger textLength = [text length];
referTotalPages = (int)totalTextSize.height/(int)textLabel.frame.size.height+1;
referCharatersPerPage = textLength/referTotalPages;

// 申请最终保存页面NSRange信息的数组缓冲区
int maxPages = referTotalPages;
rangeOfPages = (NSRange *)malloc(referTotalPages*sizeof(NSRange));
memset(rangeOfPages, 0x0, referTotalPages*sizeof(NSRange));

// 页面索引
int page = 0;

for (NSUInteger location = 0; location < textLength; ) {
// 先计算临界点（尺寸刚刚超过UILabel尺寸时的文本串）
NSRange range = NSMakeRange(location, referCharatersPerPage);

// reach end of text ?
NSString *pageText;
CGSize pageTextSize;

while (range.location + range.length < textLength) {
pageText = [text substringWithRange:range];

pageTextSize = [pageText sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE_MAX]
constrainedToSize:CGSizeMake(textLabel.frame.size.width, CGFLOAT_MAX)
lineBreakMode:UILineBreakModeWordWrap];

if (pageTextSize.height > textLabel.frame.size.height) {
break;
}
else {
range.length += referCharatersPerPage;
}
}

if (range.location + range.length >= textLength) {
range.length = textLength - range.location;
}

// 然后一个个缩短字符串的长度，当缩短后的字符串尺寸小于textLabel的尺寸时即为满足
while (range.length > 0) {
pageText = [text substringWithRange:range];

pageTextSize = [pageText sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE_MAX]
constrainedToSize:CGSizeMake(textLabel.frame.size.width, CGFLOAT_MAX)
lineBreakMode:UILineBreakModeWordWrap];

if (pageTextSize.height <= textLabel.frame.size.height) {
range.length = [pageText length];
break;
}
else {
range.length -= 2;
}
}

// 得到一个页面的显示范围
if (page >= maxPages) {
maxPages += 10;
rangeOfPages = (NSRange *)realloc(rangeOfPages, maxPages*sizeof(NSRange));
}
rangeOfPages[page++] = range;

// 更新游标
location += range.length;
}

// 获取最终页面数量
totalPages = page;

// 更新UILabel内容
textLabel.text = [text substringWithRange:rangeOfPages[currentPage]];
}
}

// 显示当前页面进度信息，格式为："8/100"
pageInfoLabel.text = [NSString stringWithFormat:@"%d/%d", currentPage+1, totalPages];
}

////////////////////////////////////////////////////////////////////////////////////////
// 上一页
- (IBAction)actionPrevious:(id)sender {
if (currentPage > 0) {
currentPage--;

NSRange range = rangeOfPages[currentPage];
NSString *pageText = [text substringWithRange:range];

textLabel.text = pageText;

//
pageInfoLabel.text = [NSString stringWithFormat:@"%d/%d", currentPage+1, totalPages];
}
}

////////////////////////////////////////////////////////////////////////////////////////
// 下一页
- (IBAction)actionNext:(id)sender {
if (currentPage < totalPages-1) {
currentPage++;

NSRange range = rangeOfPages[currentPage];
NSString *pageText = [text substringWithRange:range];

textLabel.text = pageText;

//
pageInfoLabel.text = [NSString stringWithFormat:@"%d/%d", currentPage+1, totalPages];
}
}转载