生成大型 PDF 时，我的应用程序收到一条内存警告，然后在 PDF 的生成过程中崩溃。PDF 被绘制到网络视图中，当页面超过一定数量（取决于设备）时，我的内存不足
到目前为止，我对此事的研究使我明白我需要：
更改UIGraphicsBeginPDFContextToData为IGraphicsBeginPDFContextToFile
创建一个合理的临时文件路径，
把它交给函数，
将文件交给 webview 加载。
完成后删除文件。
问题是，虽然我认为我（只是）主要掌握了它，但我不知道如何实现这一点，或者完全理解它以便在我的代码中实现它。在这件事上的建议非常适用
我也愿意接受任何其他想法来阻止内存崩溃
@interface ICPDFPreviewController ()
@property (nonatomic, strong) Certificate *certificate;
@property (nonatomic, strong) NSData *pdfData;
@property (nonatomic) BOOL viewHasUnloaded;
- (void)generatePdf;
- (void)pdfDone:(NSData *)data;
- (NSData *)createPdfWithPages:(NSArray *)pages;
@end
@implementation ICPDFPreviewController
@synthesize certificate=_certificate;
@synthesize scrollView=_scrollView;
@synthesize webView=_webView;
@synthesize pdfData=_pdfData;
@synthesize viewHasUnloaded=_viewHasUnloaded;
- (void)generatePdf
{
NSMutableArray *pagesArray = [NSMutableArray array];
if ([self.certificate.certificateType.title isEqualToString:@"Minor Works"]) {
[pagesArray addObject:[[ICPDFMinorWorksPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFMinorWorksPage2 alloc] initWithCertificate:self.certificate]];
} else if ([self.certificate.certificateType.title isEqualToString:@"EIC"]) {
[pagesArray addObject:[[ICPDFEICPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage2 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage3 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage4 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICPage5 alloc] initWithCertificate:self.certificate]];
[self addDistributionBoardsToPagesArray:pagesArray];
ICPDFEICPageFinal *pageFinal = [[ICPDFEICPageFinal alloc] initWithCertificate:self.certificate];
pageFinal.pageNumber.text = [NSString stringWithFormat:@"%d", pagesArray.count+1];
[pagesArray addObject:pageFinal];
} else if ([self.certificate.certificateType.title isEqualToString:@"Domestic EIC"]) {
[pagesArray addObject:[[ICPDFDomesticEICPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFDomesticEICPage2 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFDomesticEICPage3 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFDomesticEICPage4 alloc] initWithCertificate:self.certificate]];
[self addDistributionBoardsToPagesArray:pagesArray];
[pagesArray addObject:[[ICPDFDomesticEICPageFinal alloc] initWithCertificate:self.certificate]];
} else if ([self.certificate.certificateType.title isEqualToString:@"EICR"]) {
[pagesArray addObject:[[ICPDFEICRPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRPage2 alloc] initWithCertificate:self.certificate]];
[self addObservationsToPagesArray:pagesArray];
[self addDistributionBoardsToPagesArray:pagesArray];
[pagesArray addObject:[[ICPDFEICRInspection alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRInspectionPage1 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRInspectionPage2 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRInspectionPage3 alloc] initWithCertificate:self.certificate]];
[pagesArray addObject:[[ICPDFEICRPageFinal alloc] initWithCertificate:self.certificate]];
}
// Set page count on all pages
int pageNumber = 0;
for (ICCertificateComponent *page in pagesArray) {
page.pageNumber.text = [NSString stringWithFormat:@"%d", ++pageNumber];
page.pageCount.text = [NSString stringWithFormat:@"%d", pagesArray.count];
}
NSData *pdfData = [self createPdfWithPages:pagesArray];
[self performSelectorOnMainThread:@selector(pdfDone:) withObject:pdfData waitUntilDone:YES];
}
- (void)pdfDone:(NSData *)data
{
self.pdfData = data;
[self.webView loadData:self.pdfData MIMEType:@"application/pdf" textEncodingName:@"utf-8" baseURL:nil];
[ICUtils removeProgressView];
}
- (NSData *)createPdfWithPages:(NSArray *)pages
{
// Creates a mutable data object for updating with binary data, like a byte array
NSMutableData *pdfData = [NSMutableData data];
ICCertificateComponent *firstPage = [pages objectAtIndex:0];
UIGraphicsBeginPDFContextToData(pdfData, firstPage.contentView.bounds, nil);
for (int i = 0; i < pages.count; i++) {
ICCertificateComponent *thisPage = [pages objectAtIndex:i];
UIGraphicsBeginPDFPageWithInfo(thisPage.contentView.bounds, nil);
CGContextRef pdfContext = UIGraphicsGetCurrentContext();
[thisPage.contentView.layer renderInContext:pdfContext];
}
UIGraphicsEndPDFContext();
return pdfData;
}
- (void)addDistributionBoardsToPagesArray:(NSMutableArray *)pagesArray
{
int pageCount = pagesArray.count;
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"createdAt" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
NSArray *boards = [self.certificate.distributionBoards sortedArrayUsingDescriptors:sortDescriptors];
for (DistributionBoard *thisBoard in boards) {
DebugLog(@"Creating a board page");
ICPDFDistributionBoard *boardPage = [[ICPDFDistributionBoard alloc] initWithDistributionBoard:thisBoard];
boardPage.pageNumber.text = [NSString stringWithFormat:@"%d", ++pageCount];
DebugLog(@"Page number is %d", pageCount);
[pagesArray addObject:boardPage];
NSSortDescriptor *circuitDescriptor = [[NSSortDescriptor alloc] initWithKey:@"createdAt" ascending:YES];
NSArray *circuitDescriptors = [[NSArray alloc] initWithObjects:circuitDescriptor, nil];
NSArray *circuits = [thisBoard.circuits sortedArrayUsingDescriptors:circuitDescriptors];
//int circuitCount = circuits.count;
ICPDFCircuitDetails *circuitDetails = boardPage.circuitDetails;
int circuitCount = 0;
for (Circuit *thisCircuit in circuits) {
circuitCount++;
if (circuitCount > 16) {
// Add an extension page
DebugLog(@"Adding an extension sheet");
circuitCount = 1;
ICPDFDistributionBoardExtension *boardExtension = [[ICPDFDistributionBoardExtension alloc] initWithDistributionBoard:thisBoard];
[pagesArray addObject:boardExtension];
boardExtension.pageNumber.text = [NSString stringWithFormat:@"%d", ++pageCount];
circuitDetails = boardExtension.circuitDetails;
}
NSString *key = [NSString stringWithFormat:@"circuitRow%d", circuitCount];
ICCircuitRow *circuitRow = [circuitDetails valueForKey:key];
[circuitRow populateFromCircuit:thisCircuit];
}
}
}
调试控制台警告是其中的一个负载，然后崩溃
2013-02-08 10:38:35.475 iCertifi[5772:907] Received memory warning.
2013-02-08 10:38:35.477 iCertifi[5772:907] <ICPDFPreviewController: 0x1eb28930> didReceiveMemoryWarning