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82 lines
3.5 KiB
82 lines
3.5 KiB
// |
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// Placeholder.swift |
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// Kingfisher |
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// |
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// Created by Tieme van Veen on 28/08/2017. |
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// |
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// Copyright (c) 2018 Wei Wang <onevcat@gmail.com> |
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// |
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// Permission is hereby granted, free of charge, to any person obtaining a copy |
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// of this software and associated documentation files (the "Software"), to deal |
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// in the Software without restriction, including without limitation the rights |
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
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// copies of the Software, and to permit persons to whom the Software is |
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// furnished to do so, subject to the following conditions: |
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// |
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// The above copyright notice and this permission notice shall be included in |
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// all copies or substantial portions of the Software. |
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// |
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
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// THE SOFTWARE. |
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#if os(macOS) |
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import AppKit |
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#else |
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import UIKit |
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#endif |
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/// Represent a placeholder type which could be set while loading as well as |
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/// loading finished without getting an image. |
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public protocol Placeholder { |
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/// How the placeholder should be added to a given image view. |
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func add(to imageView: ImageView) |
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/// How the placeholder should be removed from a given image view. |
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func remove(from imageView: ImageView) |
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} |
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/// Default implementation of an image placeholder. The image will be set or |
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/// reset directly for `image` property of the image view. |
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extension Placeholder where Self: Image { |
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/// How the placeholder should be added to a given image view. |
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public func add(to imageView: ImageView) { imageView.image = self } |
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/// How the placeholder should be removed from a given image view. |
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public func remove(from imageView: ImageView) { imageView.image = nil } |
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} |
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extension Image: Placeholder {} |
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/// Default implementation of an arbitrary view as placeholder. The view will be |
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/// added as a subview when adding and be removed from its super view when removing. |
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/// |
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/// To use your customize View type as placeholder, simply let it conforming to |
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/// `Placeholder` by `extension MyView: Placeholder {}`. |
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extension Placeholder where Self: View { |
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/// How the placeholder should be added to a given image view. |
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public func add(to imageView: ImageView) { |
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imageView.addSubview(self) |
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self.translatesAutoresizingMaskIntoConstraints = false |
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NSLayoutConstraint.activate([ |
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NSLayoutConstraint(item: self, attribute: .centerX, relatedBy: .equal, toItem: imageView, attribute: .centerX, multiplier: 1, constant: 0), |
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NSLayoutConstraint(item: self, attribute: .centerY, relatedBy: .equal, toItem: imageView, attribute: .centerY, multiplier: 1, constant: 0), |
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NSLayoutConstraint(item: self, attribute: .height, relatedBy: .equal, toItem: imageView, attribute: .height, multiplier: 1, constant: 0), |
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NSLayoutConstraint(item: self, attribute: .width, relatedBy: .equal, toItem: imageView, attribute: .width, multiplier: 1, constant: 0) |
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]) |
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} |
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/// How the placeholder should be removed from a given image view. |
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public func remove(from imageView: ImageView) { |
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self.removeFromSuperview() |
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} |
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}
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