斑马打印机只打印连续的多个标签，如果用户点击

Question

我有一个斑马打印机奇怪的问题。在大的图片上，我有代码来获取项目，并从队列中逐一打印。如果打印开始时，队列上有3个项目，代码将循环获取队列中的第一个数据，发送给打印机，并删除队列中的第一个数据。有点像排队。

问题是，如果是循环并将数据直接发送到打印机的代码，则打印机将只打印第一项。即使NSLog显示打印机连接打开，数据发送，打印成功，打印机连接关闭，下一个项目也消失了。

但如果每次代码打印一个标签，然后应用程序显示"按确定打印下一个标签"这样的消息框，然后用户点击确定按钮，它可以在每次点击按钮后打印第二个标签和剩余的标签。

我试着模仿这一点。我试图使用计时器来"按按钮编程"[btnPrint sendActionsForControlEvents:UIControlEventTouchUpInside]，我也使用计时器来直接调用函数，或者给线程延迟，但没有工作。它必须从一个按钮启动，从人的触摸。我不知道为什么。

代码如下:

// main function to print
-(void) printLabel {
    if ([dataToPrint count] > 0) {
        [self printWithData:[dataToPrint objectAtIndex:0]];
    }
}
-(void)printWithData:(NSString*) data;
{
    NSString *zplString = data;
    // do something with zplString   
    NSLog(@"Sending data to printer");
    printHandler = [[PrintingHandler alloc] init];
    [printHandler setDelegate:self];
    [printHandler initialize];
    [printHandler printToSerial:bluetoothSerialNumber withData:zplString];
}
// delegate to call if the print is success
-(void) printIsSuccess
{
    [dataToPrint removeObjectAtIndex:0];
    // in here, I just use sleep code instead of button tap emulation to avoid unnecessarily too long code
    [NSThread sleepForTimeInterval:2.0f];
    [self printLabel];
}
// this is method inside PrintingHandler class that get called by PrintingHandler (printToSerial:)
-(void) printLabelWithData:(NSString*) zplData toPrinter:(NSString*) serial withSender:(id) sender
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^ {
        // Instantiate connection to Zebra Bluetooth accessory
        id<ZebraPrinterConnection, NSObject> thePrinterConn = [[MfiBtPrinterConnection alloc] initWithSerialNumber:serial];
        // Open the connection - physical connection is established here.
        BOOL success = [thePrinterConn open];
        NSError *error = nil;
        // Send the data to printer as a byte array.
        success = success && [thePrinterConn write:[zplData dataUsingEncoding:NSUTF8StringEncoding] error:&error];
        [NSThread sleepForTimeInterval:1.0f];
        //Dispath GUI work back on to the main queue!
        dispatch_async(dispatch_get_main_queue(), ^{
            if (success != YES || error != nil) {
                [delegate printFailed];
                UIAlertView *errorAlert = [[UIAlertView alloc] initWithTitle:@"Error" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];
                [errorAlert show];
                [errorAlert release];
            }
            else if (success != YES) {
                NSLog(@"Print is not success, but no error raised");
                [delegate printSuccess];
            }
            else
            {
                NSLog(@"Print is success");
                [delegate printSuccess];
            }
        });
        // Close the connection to release resources.
        NSLog(@"printer connection closed");
        [thePrinterConn close];
        [thePrinterConn release];
    });
}

Answer 1

对不起，我找到解决办法了。问题是打开连接到打印机和发送数据到打印机之间的速度太快了。

我把延迟放错位置了。

所以当前要打印的步骤是:

1. 打开蓝牙打印机连接
2. 延迟
4. 关闭打印机连接

正确的应该是:

1. 打开蓝牙打印机连接
延迟
4. 关闭打印机连接

我把答案放在这里，这样可以帮助其他有同样问题的人。

-(void) printLabelWithData:(NSString*) zplData toPrinter:(NSString*) serial withSender:(id) sender
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^ {
        // Instantiate connection to Zebra Bluetooth accessory
        id<ZebraPrinterConnection, NSObject> thePrinterConn = [[MfiBtPrinterConnection alloc] initWithSerialNumber:serial];
        // Open the connection - physical connection is established here.
        BOOL success = [thePrinterConn open];
        NSError *error = nil;
        [NSThread sleepForTimeInterval:1.0f]; // this is the important one
        // Send the data to printer as a byte array.
        success = success && [thePrinterConn write:[zplData dataUsingEncoding:NSUTF8StringEncoding] error:&error];
        //Dispath GUI work back on to the main queue!
        dispatch_async(dispatch_get_main_queue(), ^{
            if (success != YES || error != nil) {
                [delegate printFailed];
                UIAlertView *errorAlert = [[UIAlertView alloc] initWithTitle:@"Error" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];
                [errorAlert show];
                [errorAlert release];
            }
            else if (success != YES) {
                NSLog(@"Print is not success, but no error raised");
                [delegate printSuccess];
            }
            else
            {
                NSLog(@"Print is success");
                [delegate printSuccess];
            }
        });
        // Close the connection to release resources.
        NSLog(@"printer connection closed");
        [thePrinterConn close];
        [thePrinterConn release];
    });
}