Nsprintoperation上下文始终为零，导致崩溃.打印时如何设置上下文

Question

我有一个我想打印的自定义nsview。使用NSView和打印选项设置内容后，我进行此调用：

NSPrintOperation *printOperation = [NSPrintOperation printOperationWithView: printView printInfo: printInfo];
[NSPrintOperation setCurrentOperation: printOperation];
[printView beginDocument];
NSGraphicsContext* theContext = printOperation.context;

" thecontext"始终为零。如果我忽略了这一点，当我拨打这个电话时：

[printView beginPageInRect: rect atPlacement: location];

我有一个例外，说：" [常规]发送到不在窗口中的视图的lockfocus/unlockfocus"

如果我评论了这一点，我会收到一条十亿条消息，说：" cgcontextdrawpath：无效上下文0x0。如果要查看backtrace，请设置cg_context_show_show_backtrace环境变量。"打开底线只是显示我所有的图纸是引起它的原因。

如果我查看视图的" drawRect："函数：

中的图形上下文

NSGraphicsContext *graphicsContext = [NSGraphicsContext currentContext];
CGContextRef      context = [[NSGraphicsContext currentContext] graphicsPort];

GraphicsContext和上下文都是零。

那么，我该怎么做才能获得有效的打印上下文？我看到有一个Nsprintoperation方法CreateContext，但文档说不是直接称呼它，如果我忽略了这一点，它无济于事，并向打印机射击了大约八个空的作业。

最新版本的代码，该版本仍会导致无效上下文：

NSPrintOperation *printOperation = [NSPrintOperation printOperationWithView: printView printInfo: printInfo];
[printView setCurrentForm: [formSet objectAtIndex: 0]];
NSInteger pageCounter = 0;
formHeight = 0;
formWidth = 0;
for (AFVForm *oneForm in formSet)
{
    printView.verticalOffset = formHeight;
    NSRect  rect = NSMakeRect(0, 0, oneForm.pageWidth, oneForm.pageHeight);
    NSPoint location = [printView locationOfPrintRect: rect];
    formHeight += [oneForm pageHeight];
    if ([oneForm pageWidth] > formWidth)
        formWidth = [oneForm pageWidth];
    pageCounter++;
    printView.currentForm = oneForm;
    [printView setPrintMode: YES];
    [printView drawRect: NSZeroRect];
    [printView setPrintMode: NO];
}
[printOperation setShowsPrintPanel:YES];
[printOperation runOperationModalForWindow: [self window] delegate: nil didRunSelector: nil contextInfo: nil];

Answer 1

beginDocument和 beginPageInRect:atPlacement:在打印会话的开头和每个页面的开头都调用。如果您愿意，请覆盖这些方法，但不要致电。不要致电setCurrentOperation，只需创建一个NSPrintOperation并调用runOperation或runOperationModalForWindow:delegate:didRunSelector:contextInfo:。

请参阅Mac的打印编程指南

编辑，示例：

printview.h

@interface PrintView : NSView
@property (strong) NSArray *forms;
@end

printview.m

@interface PrintView ()
@property (weak) NSTextField *titleField;
@property (weak) NSDictionary *currentForm;
@end

@implementation PrintView
- (instancetype)initWithFrame:(NSRect)frameRect {
    if (self = [super initWithFrame:frameRect]) {
        // add a title text field
        NSTextField *textField = [[NSTextField alloc] initWithFrame:NSMakeRect(25.0, 225.0, 250.0, 25.0)];
        textField.alignment = NSTextAlignmentCenter;
        [self addSubview:textField];
        self.titleField = textField;
    }
    return self;
}
- (BOOL)knowsPageRange:(NSRangePointer)range {
    range->location = 1;
    range->length = self.forms.count;
    return YES;
}
- (NSRect)rectForPage:(NSInteger)page {
    return self.bounds;
}
- (void)beginPageInRect:(NSRect)rect atPlacement:(NSPoint)location {
    [super beginPageInRect:rect atPlacement:location];
    NSPrintOperation *printOperation = [NSPrintOperation currentOperation];
    self.currentForm = self.forms[printOperation.currentPage - 1];
    // set the title
    [self.titleField setStringValue:
        [NSString stringWithFormat:@"Form ‘%@’ page %li",
            self.currentForm[@"title"], (long)printOperation.currentPage]];
}
- (void)drawRect:(NSRect)dirtyRect {
    [super drawRect:dirtyRect];
    // Drawing code here.
    // draw a colored frame
    NSColor *formColor = self.currentForm[@"color"];
    NSRect rect = self.bounds;
    NSInsetRect(rect, 20.0, 20.0);
    [formColor set];
    NSFrameRect(rect);
}
@end

其他地方

- (IBAction)printAction:(id)sender {
    PrintView *printView = [[PrintView alloc] initWithFrame:NSMakeRect(0.0, 0.0, 300.0, 300.0)];
    printView.forms = @[
            @{@"title":@"Form A", @"color":[NSColor redColor]},
            @{@"title":@"Form B", @"color":[NSColor greenColor]},
            @{@"title":@"Form C", @"color":[NSColor blueColor]},
        ];
    NSPrintOperation *printOperation = [NSPrintOperation printOperationWithView:printView];
    [printOperation setShowsPrintPanel:YES];
    [printOperation runOperationModalForWindow:[self window] delegate:nil didRunSelector:NULL contextInfo:NULL];
}

Answer 2

一个快速的示例，在您的NSView子类中。如果没有帮助，我深表歉意：

         func letsPrint() {
             let pInfo = NSPrintInfo.shared
             let d = pInfo.dictionary()
             d["NSLastPage"] = 1
             super.printView(self)
         }
         override func knowsPageRange(_ range: NSRangePointer) -> Bool {
             return true
         }
         override func rectForPage(_ page: Int) -> NSRect {
             if page > 1 { return NSZeroRect }
             return NSRect(x: 0, y: 0, width: 612, height: 792)
         }

此示例打印1页，8.5 x 11，因此在RectforPage中的常数

LETSPRINT连接到应用程序菜单第一响应者。