当我从屏幕导航回来并再次进入屏幕时,nextTrackCommand
的目标被多次调用,即使我在 viewWillDisappear
中删除了目标。我做错了什么?
override func viewDidLoad() {
super.viewDidLoad()
UIApplication.shared.beginReceivingRemoteControlEvents()
MPRemoteCommandCenter.shared().nextTrackCommand.addTarget { [unowned self] (_) -> MPRemoteCommandHandlerStatus in
print("go to next track")
return .success
}
}
override func viewWillDisappear(_ animated: Bool) {
MPRemoteCommandCenter.shared().nextTrackCommand.removeTarget(self)
}
最佳答案
addTarget
的过载您正在调用的不会将 self
添加为目标。它添加了一个您之前不知道的 NSObject
对象作为目标。 它返回这个对象。所以如果你想删除它,你应该得到它的返回值,把它保存在一个属性中,这样你就可以把它传递给removeTarget
。
Call the
addTarget(handler:)
method to add a block to be called. Remove the handler by calling theremoveTarget(_:)
method, passing in the object returned by this method.
var target: NSObject?
override func viewDidLoad() {
super.viewDidLoad()
UIApplication.shared.beginReceivingRemoteControlEvents()
target = MPRemoteCommandCenter.shared().nextTrackCommand.addTarget { [unowned self] (_) -> MPRemoteCommandHandlerStatus in
print("go to next track")
return .success
}
}
override func viewWillDisappear(_ animated: Bool) {
MPRemoteCommandCenter.shared().nextTrackCommand.removeTarget(target)
}
或者,调用 other overload这实际上允许您将 self
添加为目标。
https://stackoverflow.com/questions/65055851/