當拖動MKAnnotationView時如何獲得連續回撥

Question

我有MKAnnotationView這是拖拽能力，並且我實現了didChangeDragState:委託方法，在拖拽的開始和結束處獲得回調，但不是連續的。我想跟蹤當前拖動的註釋座標，請幫助我解決一些問題。謝謝。

Answer 1

的座標可以從annotationview.coordinates可以得到：

-(void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view 
    didChangeDragState:(MKAnnotationViewDragState)newState fromOldState: 
    (MKAnnotationViewDragState)oldState 
    { 
    CLLocationCoordinate2D currentCoordinates = view.annotation.coordinate; 
    } 

Answer 2

據我所知，沒有爲你做這個蘋果提供的方式，但你可以通過志願實現它（ h/t到this answer）。

您還需要手動確定註解視圖的座標，因爲註釋的座標只有在輸入MKAnnotationViewDragStateEnding之後纔會更新。

完整的解決方案是這樣的：

// Somewhere in your code before the annotation view gets dragged, subscribe your observer object to changes in the annotation view's frame center 
annotationView.addObserver(DELEGATE_OBJECT, forKeyPath: "center", options: NSKeyValueObservingOptions.New, context: nil) 

// Then in the observer's code, fill out the KVO callback method 
// Your observer will need to conform to the NSKeyValueObserving protocol -- all `NSObject`s already do 
override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) { 
    // Check that we're observing an annotation view. The `where` clause can be omitted if you're only observing changes in its frame, or don't care about extra calls 
    if let annotationView = object as? MKAnnotationView where keyPath == "center" { 
     // Defined below, `coordinateForAnnotationView` converts a CGPoint measured within a given MKMapView to the geographical coordinate represented in that location 
     let newCoordinate = coordinateForAnnotationView(pin, inMapView: self.mapView) 

     // Do stuff with `newCoordinate` 
    } 
} 

func coordinateForAnnotationView(annotationView: MKAnnotationView, inMapView mapView: MKMapView) -> CLLocationCoordinate2D { 
    // Most `MKAnnotationView`s will have a center offset, including `MKPinAnnotationView` 
    let trueCenter = CGPoint(x: annotationView.center.x - annotationView.centerOffset.x, 
     y: annotationView.center.y - annotationView.centerOffset.y) 

    return mapView.convertPoint(trueCenter, toCoordinateFromView: mapView) 
}