ios - Objective-C NSData 返回 nil

Question

我这里有一个方法可以创建 PDF 和 PDF 的 URL。我的问题是我试图返回 PDF 的 NSData，但是当我在方法末尾尝试时它返回 nil。为什么它返回 nil ？我该如何解决这个问题？

- (NSData *) setProductionSchedulePDF
{
    NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *filename = @"test.pdf";
    NSURL *fileURL = [NSURL fileURLWithPathComponents:[NSArray arrayWithObjects:documentsDirectory, filename, nil]];

    CGContextRef pdfContext = CGPDFContextCreateWithURL((CFURLRef)fileURL, NULL, NULL);
    CGPDFContextBeginPage(pdfContext, NULL);
    UIGraphicsPushContext(pdfContext);

    CGRect bounds = CGContextGetClipBoundingBox(pdfContext);
    CGContextScaleCTM(pdfContext, 1.0, -1.0);
    CGContextTranslateCTM(pdfContext, 0.0, -bounds.size.height);

    NSArray *taskArray = self.taskData;

    UIFont *headerFont = [UIFont fontWithName:@"Arial" size:8];

    UIFont *font = [UIFont fontWithName:@"Arial" size:6];

    NSDictionary *attributes = @{ NSFontAttributeName: font};

    NSDictionary *headerAttributes = @{ NSFontAttributeName: headerFont};

    [@"Task" drawAtPoint:CGPointMake(10, 10) withAttributes:headerAttributes];

    int counter = 0;
    for (id object in taskArray) {
        [object drawAtPoint:CGPointMake(10, 10.5 * counter + 30) withAttributes:attributes];
        counter++;
    }

    int keyCounter = 0;
    for(id object in self.prodSchedSortedKeys) {
        [object drawAtPoint:CGPointMake(60 * keyCounter + 90, 10) withAttributes:headerAttributes];
        NSArray *bfsmArray;

        if([finalProductionSchedule count]!=0)
        {
            bfsmArray = [finalProductionSchedule valueForKey:object];
        }
        else
        {
            bfsmArray = nil;
        }

        bfsmArray = nil;

        int valueCounter = 0;
        for(id object2 in bfsmArray)
        {
            if(bfsmArray != nil)
            {

                if(valueCounter == 13 || valueCounter == 66 || valueCounter == 67){

                    [[bfsmArray objectAtIndex:valueCounter] drawAtPoint:CGPointMake(60 * keyCounter + 90, 10.5 * valueCounter + 30) withAttributes:attributes];

                }
                else if (valueCounter == 68 || valueCounter == 69)
                {
                    [[[bfsmArray objectAtIndex:valueCounter] baseLineStart] drawAtPoint:CGPointMake(60 * keyCounter + 90, 10.5 * valueCounter + 30) withAttributes:attributes];
                }
                else
                {
                    if([[[bfsmArray objectAtIndex:valueCounter] baseLineStart] isEqualToString:@""] && [[[bfsmArray objectAtIndex:valueCounter] actualFinish] isEqualToString:@""]){

                    }
                    else
                    {
                        [[NSString stringWithFormat:@"%@ / %@",[[bfsmArray objectAtIndex:valueCounter] baseLineStart],[[bfsmArray objectAtIndex:valueCounter] actualFinish]] drawAtPoint:CGPointMake(60 * keyCounter + 90, 10.5 * valueCounter + 30) withAttributes:attributes];
                    }
                }

            }
            NSLog(@"%@", object2);
            valueCounter++;
        }
        keyCounter++;
    }

    UIGraphicsPopContext();
    CGPDFContextEndPage(pdfContext);
    CGPDFContextClose(pdfContext);

    NSString *myString = [fileURL absoluteString];

    NSData *pdfData = [NSData dataWithContentsOfFile:myString];

    return pdfData;
}

更新

我像这样添加了 NSError:

NSError *error;
    NSData *pdfData = [NSData dataWithContentsOfFile:myString options:nil error:&error];

    NSLog(@"%@", error);

并且 NSError 返回以下内容:

error   NSError *   domain: @"NSCocoaErrorDomain" - code: 260   0x16820310

这是错误的控制台日志:

Error Domain=NSCocoaErrorDomain Code=260 "The file “test.pdf” couldn’t be opened because there is no such file." UserInfo={NSFilePath=file:///var/mobile/Containers/Data/Application/A2C316BA-97DF-4560-8F6D-BA6A15B2CCA3/Documents/test.pdf, NSUnderlyingError=0x155420e0 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}}

Answer 1

更改:

NSString *myString = [fileURL absoluteString];

致:

NSString *myString = [fileURL path];

原因是[NSData dataWithContentsOfFile:]需要一个路径，即/some/dir/file.pdf。 absoluteString 返回一个 URL，即:file://some/dir/file.pdf。

您可以在 question 中详细了解 path 和 absoluteString 之间的差异。 .