ios - 如何在ios中检查打印机？

Question

如何知道打印机连接是否可用？我们也可以让点击打印按钮自动打印一份到默认打印机吗？

我试过下面的代码..

- (void)viewDidLoad {

    if (![UIPrintInteractionController isPrintingAvailable])

        [myPrintButton removeFromSuperView];

    // other tasks...

}

 -(void)print_touchUpInside :(id)sender
{
    UIPrintInteractionController *controller = [UIPrintInteractionController sharedPrintController];
    if(!controller){
        NSLog(@"Couldn't get shared UIPrintInteractionController!");
        return;
    }

    UIPrintInteractionCompletionHandler completionHandler =
    ^(UIPrintInteractionController *printController, BOOL completed, NSError *error) {
        if(!completed && error){
            NSLog(@"FAILED! due to error in domain %@ with error code %u", error.domain, error.code);
        }
    };

    UIPrintInfo *printInfo = [UIPrintInfo printInfo];
    printInfo.outputType = UIPrintInfoOutputGeneral;
    printInfo.jobName = @"print";
    printInfo.duplex = UIPrintInfoDuplexLongEdge;
    controller.printInfo = printInfo;
    controller.showsPageRange = YES;

    APLPrintPageRenderer *myRenderer = [[APLPrintPageRenderer alloc] init];
    myRenderer.jobTitle = printInfo.jobName;
    UIViewPrintFormatter *viewFormatter = [self.webView viewPrintFormatter];
    UIFont *font = [UIFont fontWithName:@"Helvetica" size:HEADER_FOOTER_TEXT_HEIGHT];
    CGSize titleSize = [myRenderer.jobTitle sizeWithFont:font];
    myRenderer.headerHeight = myRenderer.footerHeight = titleSize.height + HEADER_FOOTER_MARGIN_PADDING;
    [myRenderer addPrintFormatter:viewFormatter startingAtPageAtIndex:0];
    controller.printPageRenderer = myRenderer;
    [controller presentAnimated:YES completionHandler:completionHandler];

}