ios-文件预览-QLPreViewController

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最近在做的项目中有相关pdf文件预览的功能，所以了解了一下相关的资料。基本上网上给出来的方法有两种，分别是用UIWebVie和CGContextDrawPDFPage,可以点击查看,但是本文所要讲的是另外一种方式-----使用QLPreViewController进行预览，QLPreViewController不仅支持PDF，还支持其他多种文件的预览，可谓功能强大。

先看下官方文档的说法：

A displayed preview includes a title taken from the last path component of the item URL. You can override this by implementing a previewItemTitle accessor for the preview item.

A Quick Look preview controller can display previews for the following items:

iWork documents
Microsoft Office documents (Office ‘97 and newer)
Rich Text Format (RTF) documents
PDF files
Images
Text files whose uniform type identifier (UTI) conforms to the public.text type (see Uniform Type Identifiers Reference)
Comma-separated value (csv) files

使用方式：

1.首先新建一个QLPreviewController对象preview；

2.遵循协议QLPreviewControllerDataSource，设置代理；

3.实现协议方法：返回文档数量方法- (NSInteger)numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller；

返回URL的方法 - (id <QLPreviewItem>)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index；

4.模态或push出QLPreviewController的对象preview。

关键代码：

#pragma mark -QLPreviewControllerDataSource- (NSInteger)numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller {    return 1;}- (id<QLPreviewItem>)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index {        NSString *filePath = [[HKClassRoomManager sharedInstance] getFilePath:self.classFile];        NSAssert(filePath, @"preview nil item");        NSFileManager* fileManager = [NSFileManager defaultManager];    NSError* error = nil;    if ([fileManager fileExistsAtPath:filePath]) {        NSDictionary* fileInfo = [fileManager attributesOfItemAtPath:filePath                                                               error:&error];        NSInteger fileSize = [[fileInfo objectForKey:NSFileSize] integerValue];        if (fileSize >= 1024 * 1024 * 10) {            [NSObject showHudTipStr:@"文件较大,加载可能需要一段时间，请等待...."];        }    }        NSData *fileData = [NSData dataWithContentsOfFile:filePath];        //判断是UNICODE编码    NSString *isUNICODE = [[NSString alloc] initWithData:fileData encoding:NSUTF8StringEncoding];        //还是ANSI编码    NSString *isANSI = [[NSString alloc] initWithData:fileData encoding:-2147482062];        if (isUNICODE) {                NSString *retStr = [[NSString alloc]initWithCString:[isUNICODE UTF8String] encoding:NSUTF8StringEncoding];        NSData *data = [retStr dataUsingEncoding:NSUTF16StringEncoding];        NSError *error = nil;        [data writeToFile:filePath options:NSDataWritingAtomic error:&error];    }    else if(isANSI){                NSData *data = [isANSI dataUsingEncoding:NSUTF16StringEncoding];        NSError *error = nil;        [data writeToFile:filePath options:NSDataWritingAtomic error:&error];    }            NSURL *fileURL = [NSURL fileURLWithPath:filePath];    return fileURL;}

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