iOS实现pdf文件预览，上下翻页、缩放，读取pdf目录

最近有个朋友想做一个pdf预览，要求能够上下滑动翻页、带缩放、目录跳转功能。

因为之前我只做过简单的预览，那时直接用uiwebview实现的，这次找了下资料，发现一个比较好的库。

其原理实现：

自定义uiview来显示pdf+使用的是苹果官方的api读取目录+uiscrollview实现缩放及翻页。

不过这个库是左右翻页的，我不是很习惯，就改成了上下滑动翻页，并且在底部添加了页码显示（1/10格式）。

效果图如下：

其中几段核心代码：

1、加载pdf文件

CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), (__bridge CFStringRef)@"002.pdf", NULL, NULL);
    pdfDocument = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
    CFRelease(pdfURL);

2、获取pdf文件目录

#pragma mark 获取pdf文件目录
- (NSArray *)getPDFContents: (CGPDFDocumentRef) myDocument
{
    
    CGPDFDictionaryRef mycatalog= CGPDFDocumentGetCatalog(myDocument);
    CommentNode *rootNode = [[CommentNode alloc] initWithCatalog:mycatalog];
    CommentNode *rootOutlineNode = [rootNode childrenForName:@"/Outlines"];
    CommentNode *pagesNode = [rootNode childrenForName:@"/Pages"];
    NSArray *pagesArray = [self getPagesFromPagesNode:pagesNode];
    CommentNode *destsNode = [rootNode childrenForName:@"/Dests"];
    
    return [self getContentsForOutlineNode:rootOutlineNode pages:pagesArray destsNode:destsNode];
}

- (NSArray *)getContentsForOutlineNode:(CommentNode *)rootOutlineNode pages:(NSArray *)pagesArray destsNode:(CommentNode *)destsNode
{
    NSMutableArray *outlineArray = [[NSMutableArray alloc] init];
    CommentNode *firstOutlineNode = [rootOutlineNode childrenForName:@"/First"];
    CommentNode *outlineNode = firstOutlineNode;
    while (outlineNode) {
        NSString *title = [[outlineNode childrenForName:@"/Title"] value];
        CommentNode *destNode = [outlineNode childrenForName:@"/Dest"];
        NSMutableDictionary *outline = [NSMutableDictionary dictionaryWithDictionary:@{@"Title": title}];
        int index = 0;
        if (destNode) {
            if ([[destNode typeAsString] isEqualToString:@"Array"]) {
                CGPDFObjectRef dest = (__bridge CGPDFObjectRef)[[[destNode children] objectAtIndex:0] object];
                index = [self getIndexInPages:pagesArray forPage:dest];
            } else if ([[destNode typeAsString] isEqualToString:@"Name"]) {
                NSString *destName = [destNode value];
                CGPDFObjectRef dest = (__bridge CGPDFObjectRef)[[[[[destsNode childrenForName:destName] childrenForName:@"/D"] children] objectAtIndex:0] object];
                index = [self getIndexInPages:pagesArray forPage:dest];
            }
        } else {
            CommentNode *aNode = [outlineNode childrenForName:@"/A"];
            if (aNode) {
                CommentNode *dNode = [aNode childrenForName:@"/D"];
                if (dNode) {
                    CommentNode *d0Node = [[dNode children] objectAtIndex:0];
                    if ([[d0Node typeAsString] isEqualToString:@"Dictionary"]) {
                        CGPDFObjectRef dest = (CGPDFObjectRef)[d0Node object];
                        index = [self getIndexInPages:pagesArray forPage:dest];
                    }
                }
            }
        }
        [outline setObject:@(index) forKey:@"Index"];
        NSArray *subOutlines = [self getContentsForOutlineNode:outlineNode pages:pagesArray destsNode:destsNode];
        [outline setObject:subOutlines forKey:@"SubContents"];
        [outlineArray addObject:outline];
        outlineNode = [outlineNode childrenForName:@"/Next"];
    }
    return outlineArray;
}

- (NSArray *)getPagesFromPagesNode:(CommentNode *)pagesNode
{
    NSMutableArray *pages = [NSMutableArray new];
    CommentNode *kidsNode = [pagesNode childrenForName:@"/Kids"];
    for (CommentNode *node in [kidsNode children]) {
        NSString *type = [[node childrenForName:@"/Type"] value];
        if ([type isEqualToString:@"/Pages"]) {
            NSArray *kidsPages = [self getPagesFromPagesNode:node];
            [pages addObjectsFromArray:kidsPages];
        } else {
            [pages addObject:node];
        }
    }
    return pages;
}

- (int)getIndexInPages:(NSArray *)pages forPage:(CGPDFObjectRef)page
{
    for (int k = 0; k < pages.count; k++) {
        CommentNode *node = [pages objectAtIndex:k];
        if ([node object] == page)
            return k+1;
    }
    return 1;
}

源码获取：https://github.com/TangledHusky/YJ-PDFReader/tree/master

特别鸣谢：

参考文献：https://blog.csdn.net/shenshucong520/article/details/51578695