Question

从iOS 8开始，Apple已经通过蓝牙LE为Midi提供了外围和中央角色选项。正如他们所建议的那样，添加Peripheral ViewController应该像包含以下代码一样简单，我已经完成了。只需单击UI按钮

即可执行此方法

CABTMIDILocalPeripheralViewController *midiPeripheralController = [[CABTMIDILocalPeripheralViewController alloc] init];
[self.navigationController pushViewController:midiPeripheralController animated:YES];

执行时，将返回以下错误。如何防止此错误？

***由于未捕获的异常'NSRangeException'终止应用程序，原因：'无法删除密钥路径“parentViewController”的观察者，因为它未注册为观察者。'

Answer 1

import UIKit
import CoreAudioKit

class ViewController: UIViewController {

    var localPeripheralViewController:CABTMIDILocalPeripheralViewController?

    override func viewDidLoad() {
        super.viewDidLoad()
        localPeripheralViewController = CABTMIDILocalPeripheralViewController()

    }

    @IBAction func local(sender: AnyObject) {
        self.navigationController?.pushViewController(localPeripheralViewController!, animated: true)
    }
}

Answer 2

当CABTMIDILocalPeripheralViewController要关闭时，实际上会删除预定义的密钥@"parentViewController"，由于当时未设置该密钥，因此无法将其删除，因此抛出异常。这意味着您必须自己添加该观察者，以避免违反KVO编程。在使用

的Objective-c中的示例

-(void)yourActionOnSomeButton:(UIButton *)sender {
    // ... here is your build up code of the CABTMIDILocalPeripheralViewController

    // ... but before presenting the navController you add Observer yourself,
    // so it can be removed when dismissing or "done"
    UIButton *button = (UIButton *)sender;
    popC.sourceView = button.superview;
    [popC addObserver:self forKeyPath:@"parentViewController" options:(NSKeyValueObservingOptionNew) context:nil];
    [self presentViewController:navController animated:YES completion:nil];
}

无法加载ViewController：CABTMIDILocalPeripheralViewController

2 个答案: