我正在将我的 swift 应用程序连接到低功耗蓝牙外围设备。我是 Swift 的新手，我的问题完全与快速编码有关，而不是 BLE。
我监听外围设备以查看按钮是否被按下。我定义了一个标签并为其分配了一个文本。当应用检测到按下按钮时，我希望更改标签测试，但我的应用却崩溃了。
你可以在这里看到我的代码:
import CoreBluetooth
import UIKit
class ViewController: UIViewController, CBCentralManagerDelegate, CBPeripheralDelegate {
var manager:CBCentralManager!
var peripheral:CBPeripheral!
@IBOutlet weak var statusLabel: UILabel!
let BEAN_NAME = "Security Tag"
let BEAN_SCRATCH_UUID = CBUUID(string: "00001C0F-D102-11E1-9B23-000EFB0000A7")
let BEAN_SERVICE_UUID = CBUUID(string: "00001c00-d102-11e1-9b23-000efb0000a7")
override func viewDidLoad() {
super.viewDidLoad()
manager = CBCentralManager(delegate: self, queue: nil)
}
func centralManagerDidUpdateState(_ central:CBCentralManager) {
if central.state == CBManagerState.poweredOn {
central.scanForPeripherals(withServices: nil, options: nil)
debugPrint("Searching ...")
} else {
debugPrint("Bluetooth not available.")
}
}
func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
let device = (advertisementData as NSDictionary).object(forKey: CBAdvertisementDataLocalNameKey) as? NSString
if device?.contains(BEAN_NAME) == true {
debugPrint("Found Bean.")
self.manager.stopScan()
self.peripheral = peripheral
self.peripheral.delegate = self
manager.connect(peripheral, options: nil)
}
}
func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
debugPrint("Getting services ...")
peripheral.discoverServices(nil)
}
func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
for service in peripheral.services! {
let thisService = service as CBService
debugPrint("Service: ", service.uuid)
if service.uuid == BEAN_SERVICE_UUID {
debugPrint("Using scratch.")
peripheral.discoverCharacteristics(nil, for: thisService)
}
}
}
func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
debugPrint("Enabling ...")
for characteristic in service.characteristics! {
let thisCharacteristic = characteristic as CBCharacteristic
debugPrint("Characteristic: ", thisCharacteristic.uuid)
if thisCharacteristic.uuid == BEAN_SCRATCH_UUID {
debugPrint("Set to notify: ", thisCharacteristic.uuid)
// Prepare to show data
self.peripheral.setNotifyValue(true, for: thisCharacteristic)
}
}
}
func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
if characteristic.uuid == BEAN_SCRATCH_UUID {
let content = String(data: characteristic.value!, encoding: String.Encoding.utf8)
debugPrint("Notified.")
self.statusLabel.text = "Your Purchase is Registered."
}
}
func centralManager(_ central: CBCentralManager, didDisconnectPeripheral peripheral: CBPeripheral, error: Error?) {
debugPrint("Disconnected.")
central.scanForPeripherals(withServices: nil, options: nil)
// Hide respective user interface
}
}
一行内容为:self.statusLabel.text =“您的购买已注册。”
是我得到异常的地方。
这是我得到的错误:
2017-02-06 13:42:19.825869 kevinbletest[2143:695095] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
"<NSLayoutConstraint:0x17008b130 UILabel:0x11dd0cbf0'Waiting for a Purchase Co...'.width == 270 (active)>",
"<NSLayoutConstraint:0x17008b770 UILabel:0x11dd0cbf0'Waiting for a Purchase Co...'.centerX == UIView:0x11dd0c850.centerX (active)>",
"<NSLayoutConstraint:0x17008b7c0 UILabel:0x11dd0cbf0'Waiting for a Purchase Co...'.leading == UIView:0x11dd0c850.leadingMargin + 50 (active)>",
"<NSLayoutConstraint:0x17408c3f0 'UIView-Encapsulated-Layout-Width' UIView:0x11dd0c850.width == 375 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x17008b130 UILabel:0x11dd0cbf0'Waiting for a Purchase Co...'.width == 270 (active)>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
fatal error: unexpectedly found nil while unwrapping an Optional value
2017-02-06 13:42:25.299886 kevinbletest[2143:695095] fatal error: unexpectedly found nil while unwrapping an Optional value
(lldb)
最佳答案
根据我的阅读，错误在于:
<NSLayoutConstraint:0x17008b130 UILabel:0x11dd0cbf0'Waiting for a Purchase Co...'.width == 270 (active)>
如果您在下面阅读它，似乎 NSLayout 试图将宽度为 270 的标签居中，但失败了，因为您的文本大于 270。
在下面它说你的应用程序崩溃是因为你的标签实际上是零。
尝试 printf(self.myLabel) 看看它是否为 nil。
如果您将标签添加到 Storyboard 中并在 viewDidAppear 完成之前按下按钮，您的标签可能为零。
也可以不受任何限制地尝试。只需删除约束。
+ 等待 ViewController 加载(viewDidAppear)，然后点击。
你的应用程序崩溃是因为它解包了一个 nil 的可选值，而不是因为约束。
关于ios - 将尝试通过打破约束来恢复 <NSLayoutConstraint :0x17008b130 UILabel，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42065307/