设置为属性

@property (nonatomic ,strong) UIDocumentInteractionController *documentInteractionController;

创建

- ( void )setupDocumentControllerWithURL:( NSURL *)url
{
    if ( self.documentInteractionController == nil ){
        self.documentInteractionController = [ UIDocumentInteractionController interactionControllerWithURL :url];
    self.documentInteractionController.delegate = self ;
    }
    else {
        self.documentInteractionController.URL = url;
    }
 }

  /**
  *  打开文件
  */
-(void)openFileWithPath:(NSString*)path{
NSURL* URL = [NSURL fileURLWithPath:path];
if (URL) {
[ self setupDocumentControllerWithURL :URL];
// CGRect rect = CGRectMake ( 0 , 0 , kScreenW , kScreenH);
// [self.documentInteractionController presentOptionsMenuFromRect:rect inView:self.view  animated:YES];//包含快速预览菜单
[self.documentInteractionController presentPreviewAnimated:YES];
}
}

必须需要实现代理方法才能预览

/**
*  预览用的Controller
*/
-(UIViewController *)documentInteractionControllerViewControllerForPreview:(UIDocumentInteractionController *)controller{
return self;
}

/**
*  预览用的View
*/
-(UIView *)documentInteractionControllerViewForPreview:(UIDocumentInteractionController *)controller{
return self.view;
}

- (void)documentInteractionControllerWillBeginPreview:(UIDocumentInteractionController *)controller{
NSLog(@"will begin preview");
}

- (void)documentInteractionControllerDidEndPreview:(UIDocumentInteractionController *)controller{
NSLog(@"did end preview");
}

这样使用是可以了.当你要在下载文件完成后打开文件,会这样写

NSData *data = responseObject;
BOOL isWrite = [data writeToFile:[MyTools filePathInTmpWithFile:fileName] atomically:YES];
MAIN(^{
[self.mbHud hideAnimated:YES];
});
if (isWrite) {//调用打开文件
[self openFileWithPath:[MyTools filePathInTmpWithFile:fileName]];
}else{
MAIN(^{
[MyTools showAlertWithTitle:kLocStr(@"提示") andContent:kLocStr(@"打开文件失败!") andBlock:nil atController:self];
});
}

这样会出现问题,当下载的过程中,退出当前页面,下载会继续的,下载完成后继续运行你的代码打开文件进行预览,虽然你看不到这个过程,但是确实是这样的,而且会造成当前控制器无法释放,造成内存泄漏!

解决办法:

@property (nonatomic ,assign) BOOL isAppear;         //判断是否当前页面正在显示
 - (void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
self.isAppear = NO;
if (self.documentInteractionController) {
self.documentInteractionController.delegate = nil;
NSLog(@"\\ndelegate == nil\\n");
}
}

- (void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
self.isAppear = YES;
if (self.documentInteractionController) {
self.documentInteractionController.delegate = self;
}
}



- ( void )setupDocumentControllerWithURL:( NSURL *)url
{
if (!self.isAppear) {
return;
}
if ( self.documentInteractionController == nil ){
self.documentInteractionController = [ UIDocumentInteractionController interactionControllerWithURL :url];
self.documentInteractionController.delegate = self ;
}
else {
self.documentInteractionController.URL = url;
}
}

- (void)documentInteractionControllerDidEndPreview:(UIDocumentInteractionController *)controller{
NSLog(@"did end preview");
self.documentInteractionController = nil;
}

这样就可以了!