如何在 Cocoa 中将 NSImageView 移动到 NSView 中？

Question

在我的 Mac OS 应用程序中，我需要一个功能，以便能够在此 NSImageView 中发生 mouseDown 事件（由用户触发）后在 NSView 内部移动 NSImageView。当用户触发鼠标 Up 事件时，此视图必须移动到最后一个 mouseDrag 事件方向并停留在那里。在移动过程中，我希望 NSImageView 在屏幕上可见（它应该与鼠标光标一起移动）。

我读过 Apple 的处理鼠标事件指南，https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/EventOverview/HandlingMouseEvents/HandlingMouseEvents.html 我还下载了这个示例代码：https://developer.apple.com/library/content/samplecode/DragItemAround/Introduction/Intro.html

两个链接都包含 Objective C 中的代码。 DragItemAround 的代码已过时。我试图在 GitHub 和其他 Whosebug 线程上搜索解决方案，但没有找到任何有效的解决方案。

很高兴听到这个问题的答案。我正在使用 Swift 3.

我创建了一个自定义的 MovableImageView，它是 NSImageView 的子class，代码如下：

import Cocoa

class MovableImageView: NSImageView {

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)

        // Drawing code here.
        // setup the starting location of the
        // draggable item

    }

    override func mouseDown(with event: NSEvent) {
        Swift.print("mouseDown")

        //let window = self.window!
        //let startingPoint = event.locationInWindow


    }


    override func mouseDragged(with event: NSEvent) {
        Swift.print("mouseDragged")

        self.backgroundColor = NSColor.black

    }

    override func mouseUp(with event: NSEvent) {
        Swift.print("mouseUp")
    }

}

之后，我在 Interface Builder 中将此 class 设置为 NSImageView。我还在 Interface Builder 中为此 NSImageView 设置了约束。

现在我想知道如何在 NSView 中移动 NSImageView？ (Swift 3, XCode 8)

Answer 1

您需要保存mouseDown 点，稍后用于偏移。请检查以下代码：

class MovableImageView: NSImageView {

var firstMouseDownPoint: NSPoint = NSZeroPoint

init() {
    super.init(frame: NSZeroRect)
    self.wantsLayer = true
    self.layer?.backgroundColor = NSColor.red.cgColor
}

required init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

override func draw(_ dirtyRect: NSRect) {
    super.draw(dirtyRect)

    // Drawing code here.
}

override func mouseDown(with event: NSEvent) {
    Swift.print("mouseDown")
    firstMouseDownPoint = (self.window?.contentView?.convert(event.locationInWindow, to: self))!
}

override func mouseDragged(with event: NSEvent) {
    Swift.print("mouseDragged")
    let newPoint = (self.window?.contentView?.convert(event.locationInWindow, to: self))!
    let offset = NSPoint(x: newPoint.x - firstMouseDownPoint.x, y: newPoint.y - firstMouseDownPoint.y)
    let origin = self.frame.origin
    let size = self.frame.size
    self.frame = NSRect(x: origin.x + offset.x, y: origin.y + offset.y, width: size.width, height: size.height)
}

override func mouseUp(with event: NSEvent) {
    Swift.print("mouseUp")

    }
}

在父视图中，只需将此 MovableImageView 添加为子视图，如下所示：

let view = MovableImageView()
view.frame = NSRect(x: 0, y: 0, width: 100, height: 100)
self.view.addSubview(view) //Self is your parent view

Answer 2

@brianLikeApple 回答的限制版本：

class MovableImageView: NSImageView {

var firstMouseDownPoint: NSPoint = NSZeroPoint
var xConstraint: NSLayoutConstraint!
var yContstraint: NSLayoutConstraint!

required init?(coder aDecoder: NSCoder) {
   super.init(coder: aDecoder)
    self.wantsLayer = true
    self.layer?.backgroundColor = NSColor.red.cgColor
}
override func draw(_ dirtyRect: NSRect) {
    super.draw(dirtyRect)
    
    // Drawing code here.
}

override func mouseDown(with event: NSEvent) {
    Swift.print("mouseDown")
    firstMouseDownPoint = (self.window?.contentView?.convert(event.locationInWindow, to: self))!
}

override func mouseDragged(with event: NSEvent) {
    Swift.print("mouseDragged")
    let newPoint = (self.window?.contentView?.convert(event.locationInWindow, to: self))!
    let offset = NSPoint(x: newPoint.x - firstMouseDownPoint.x, y: newPoint.y - firstMouseDownPoint.y)
    let origin = self.frame.origin
    let size = self.frame.size
    yContstraint.constant = (self.superview?.frame.height)! - origin.y - offset.y - size.height
    xConstraint.constant = origin.x + offset.x
}

override func mouseUp(with event: NSEvent) {
    Swift.print("mouseUp")
    
}

Answer 3

这是一个可以拖动的 NSView。它使用与@ExeRhythm 答案完全相同的约束。

import AppKit
class DraggableNSView: NSView {
    var down: NSPoint = NSZeroPoint
    @IBOutlet var across: NSLayoutConstraint!
    @IBOutlet var up: NSLayoutConstraint!

    override func mouseDown(with e: NSEvent) {
        down = window?.contentView?.convert(e.locationInWindow, to: self) ?? NSZeroPoint
    }

    override func mouseDragged(with e: NSEvent) {
        guard let m = window?.contentView?.convert(e.locationInWindow, to: self) else { return }
        let p = frame.origin + (m - down)
        across.constant = p.x
        up.constant = p.y
    }
}

别忘了必须在故事板中连接 across 和 up 约束！

注意。如果您更喜欢“向下”约束而不是“向上”约束，则为：

        // if you prefer a "down" constraint:
        down.constant = (superview?.frame.height)! - p.y - frame.size.height

一如既往，在你的项目中添加这两个函数，

func -(lhs: CGPoint, rhs: CGPoint) -> CGPoint {
    return CGPoint(x: lhs.x - rhs.x, y: lhs.y - rhs.y)
}

func +(lhs: CGPoint, rhs: CGPoint) -> CGPoint {
    return CGPoint(x: lhs.x + rhs.x, y: lhs.y + rhs.y)
}

请注意，您当然可以对 NSView 的任何子类（例如 NSImageView）执行此操作：

class DraggableNSImageView: NSView {
     ... same

如何在 Cocoa 中将 NSImageView 移动到 NSView 中？

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