我的 tvOS 应用程序设置的主要功能是绘制已嵌入应用程序本身的音乐表的 PDF。这里有多个选项，因为它可能只显示歌曲的某些章节。我为此使用的代码是：
- (void)drawDocument:(CGPDFDocumentRef)pdfDocument
{ NSLog(@"draw document");
// Get the total number of pages for the whole PDF document
int totalPages= (int)CGPDFDocumentGetNumberOfPages(pdfDocument);
if ([[self.arrayOfVerses firstObject] isEqualToString:@"allverses"]) {
//This is if all verses have been picked and it will do the entire PDF
NSLog(@"draw document all verses %d", totalPages);
self.pages = totalPages;
self.subtractingPages = totalPages - 1;
NSMutableArray *pageImages = [[NSMutableArray alloc] init];
// Iterate through the pages and add each page image to an array
for (int i = 1; i <= totalPages; i++) {
// Get the first page of the PDF document
CGPDFPageRef page = CGPDFDocumentGetPage(pdfDocument, i);
CGRect pageRect = CGPDFPageGetBoxRect(page, kCGPDFMediaBox);
// Begin the image context with the page size
// Also get the grapgics context that we will draw to
UIGraphicsBeginImageContext(pageRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
// Rotate the page, so it displays correctly
CGContextTranslateCTM(context, 0.0, pageRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextConcatCTM(context, CGPDFPageGetDrawingTransform(page, kCGPDFMediaBox, pageRect, 0, true));
// Draw to the graphics context
CGContextDrawPDFPage(context, page);
// Get an image of the graphics context
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[pageImages addObject:image];
}
// Set the image of the PDF to the current view
[self addImagesToScrollView:pageImages];
}
else {
//Only a certain number of verses
self.pages = [self.arrayOfVerses count];
self.subtractingPages = self.pages - 1;
NSLog (@"total pages %ld", (long)self.pages);
NSMutableArray *pageImages = [[NSMutableArray alloc] init];
[pageImages removeAllObjects];
//Getting slide numbers to be used
NSString *text = self.selectedCountry;
NSString *substring = nil;
NSRange parenRng = [text rangeOfString: @"(?<=\\().*?(?=\\))" options: NSRegularExpressionSearch];
if ( parenRng.location != NSNotFound ) {
substring = [text substringWithRange:parenRng];
NSLog(@"Substring %@", substring);
}
// Iterate through the pages and add each page image to an array
for (int i = 1; i <= totalPages; i++) {
// Get the first page of the PDF document
NSPredicate *valuePredicate=[NSPredicate predicateWithFormat:@"self.intValue == %d",i];
if ([[self.arrayOfVerses filteredArrayUsingPredicate:valuePredicate] count]!=0) {
// FOUND
CGPDFPageRef page = CGPDFDocumentGetPage(pdfDocument, i);
CGRect pageRect = CGPDFPageGetBoxRect(page, kCGPDFMediaBox);
// Begin the image context with the page size
// Also get the grapgics context that we will draw to
UIGraphicsBeginImageContext(pageRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
// Rotate the page, so it displays correctly
CGContextTranslateCTM(context, 0.0, pageRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextConcatCTM(context, CGPDFPageGetDrawingTransform(page, kCGPDFMediaBox, pageRect, 0, true));
// Draw to the graphics context
CGContextDrawPDFPage(context, page);
// Get an image of the graphics context
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[pageImages addObject:image];
}
else {
//NOT FOUND
}
}
// Set the image of the PDF to the current view
[self addImagesToScrollView:pageImages];
}
}
-(void)addImagesToScrollView:(NSMutableArray*)imageArray {
int heigth = 0;
for (UIImage *image in imageArray) {
UIImageView *imgView = [[UIImageView alloc] initWithImage:image];
imgView.contentMode = UIViewContentModeScaleAspectFit;
imgView.frame=CGRectMake(0, heigth-60, 1920, 1080);
[_scrollView addSubview:imgView];
heigth += imgView.frame.size.height;
}
}
-(void)viewDidLayoutSubviews {
_scrollView.contentSize = CGSizeMake(1920, 1080*self.pages);
}
然而，有一个部分需要下载 PDF，然后绘制。我使用 Back4app 作为它的主机，它的平均 PDF 是 420kb。我目前有它这样做：
- (void)sermonTime {
if (theImageView.hidden == NO) {
theImageView.hidden = YES;
}
if ([self.entry[@"SermonPresIncluded"] isEqualToString:@"NO"]) {
//there are some instances where there is no PDF to download, following method just displays black screen
[self blankTime];
}
else {
NSLog(@"SermonTime");
PFFileObject *thumbnail = self.entry[@"SermonPDF"];
NSString *tempDir = NSTemporaryDirectory();
NSString *pdfPath = [[tempDir stringByAppendingPathComponent:[self.entry valueForKey:@"DateOfService"]] stringByAppendingString:@".pdf"];
[thumbnail getDataInBackgroundWithBlock:^(NSData *imageData, NSError *error) {
if (error) {
NSLog(@"Error downloading PDF: %@", error);
[self blankTime];
} else {
[imageData writeToFile:pdfPath atomically:YES];
// Use completion block to signal that the PDF is ready to display
sermonPDFURL = [NSURL fileURLWithPath:pdfPath];
[self performSelector:@selector(doitnowpdf) withObject:NULL afterDelay:5];
self.view.backgroundColor = [UIColor blackColor];
}
}];
}
}
-(void)doitnowpdf {
self.arrayOfVerses = @[@"allverses"];
CGPDFDocumentRef pdfDocument = [self openPDF:sermonPDFURL];
[self drawDocument:pdfDocument];
}
我遇到了一些问题，似乎问题可能出在它试图在下载完成之前绘制 PDF，这就是为什么我在那里延迟 5 秒。然而，它仍然会搞砸，即使日志显示它在绘制开始时知道 PDF 中只有一页，所以我知道它已完全下载。发生这种情况时，上一首歌曲的 PDF 会保留在屏幕上。如果我尝试执行代码以转到下一个 PDF，它会在应该下载的内容之后转到那个，如果我返回，它会正确绘制它。我迫切希望以任何方式正确完成这项工作。
您不应使用固定的 5 秒延迟，而应使用完成处理程序来确保绘图仅在文件完全下载后发生。
` - (void)sermonTime { 如果（theImageView.hidden == NO）{ theImageView.hidden = YES; } 如果 ([self.entry[@"SermonPresIncluded"] isEqualToString:@"NO"]) { //有些情况下没有PDF可以下载，下面的方法只是黑屏 [自空白时间]; } 别的 { NSLog(@"布道时间"); PFFileObject *thumbnail = self.entry[@"SermonPDF"]; NSString *tempDir = NSTemporaryDirectory();
NSString *pdfPath = [[tempDir stringByAppendingPathComponent:[self.entry valueForKey:@"DateOfService"]] stringByAppendingString:@".pdf"];
[thumbnail getDataInBackgroundWithBlock:^(NSData *imageData, NSError *error) {
if (error) {
NSLog(@"Error downloading PDF: %@", error);
[self blankTime];
} else {
[imageData writeToFile:pdfPath atomically:YES];
sermonPDFURL = [NSURL fileURLWithPath:pdfPath];
self.arrayOfVerses = @[@"allverses"];
CGPDFDocumentRef pdfDocument = [self openPDF:sermonPDFURL];
[self drawDocument:pdfDocument];
self.view.backgroundColor = [UIColor blackColor];
}
}];
}
} `