Refresh for Swift
暴绪
//
// RefreshControl.swift
//
//
// Created by Long on 16/09/14.
// Copyright © 2016年 Apple. All rights reserved.
//
import UIKit
// 自定义下拉刷新的状态
private enum RefreshType: Int {
// 下拉刷新状态
case normal = 0
// 松手就刷新
case pulling = 1
// 正在刷新
case refreshing = 2
}
// 自定义控件的高度
private let RefreshControlHeight: CGFloat = 50
// 自定义下拉刷新控件
class RefreshControl: UIControl {
// 记录当前刷新的控件
private var currentScrollView: UIScrollView?
// 记录当前刷新状态
private var myRefreshType: RefreshType = .normal {
didSet {
switch myRefreshType {
case .normal:
print("下拉刷新")
// 箭头重置, 箭头显示, 关闭风火轮, 内容改成下拉刷新
pullDownImageView.isHidden = false
UIView.animate(withDuration: 0.25, animations: {
// 重置箭头位置
self.pullDownImageView.transform = CGAffineTransform.identity
})
indicatorView.stopAnimating()
messageLabel.text = "下拉刷新"
// 判断上一次刷新状态是正在属性,让重置默认位置
// oldValue 表示上一次存储的值
if oldValue == .refreshing {
UIView.animate(withDuration: 0.25, animations: {
// 设置停留位置, 核心代码 , 重置停留位置
self.currentScrollView?.contentInset.top -= RefreshControlHeight
})
}
case .pulling:
print("松手就刷新")
// 箭头调转, 内容修改成松手就刷新
UIView.animate(withDuration: 0.25, animations: {
// 调转箭头位置
self.pullDownImageView.transform = CGAffineTransform(rotationAngle: CGFloat(M_PI))
})
messageLabel.text = "松手就刷新"
case .refreshing:
print("正在刷新")
// 箭头隐藏, 开启风火轮, 内容改成正在刷新
pullDownImageView.isHidden = true
// 开启风火轮
indicatorView.startAnimating()
messageLabel.text = "正在刷新..."
UIView.animate(withDuration: 0.25, animations: {
// 设置停留位置, 核心代码
self.currentScrollView?.contentInset.top += RefreshControlHeight
})
// 通知外界刷新数据 (核心代码)
sendActions(for: .valueChanged)
}
}
}
// MARK: - 懒加载控件
// 下拉箭头图片
fileprivate lazy var pullDownImageView: UIImageView = UIImageView(image: UIImage(named: "tableview_pull_refresh"))
// 下拉刷新内容 label
fileprivate lazy var messageLabel: UILabel = {
let label = UILabel()
label.text = "下拉刷新"
label.font = UIFont.systemFont(ofSize: 11)
label.textColor = UIColor.gray
return label
}()
// 风火轮
fileprivate lazy var indicatorView: UIActivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: .gray)
override init(frame: CGRect) {
super.init(frame: frame)
// 获取屏幕的宽度
let screenWidth = UIScreen.main.bounds.size.width
// 设置 frame
self.frame = CGRect(x: 0, y: -RefreshControlHeight, width: screenWidth, height: RefreshControlHeight)
setupUI()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
// 添加控件设置约束
private func setupUI() {
backgroundColor = UIColor.red
// 添加子控件设置约束
addSubview(pullDownImageView)
addSubview(messageLabel)
addSubview(indicatorView)
// 使用系统布局 autolayout 需要关闭 Autoresizing
pullDownImageView.translatesAutoresizingMaskIntoConstraints = false
messageLabel.translatesAutoresizingMaskIntoConstraints = false
indicatorView.translatesAutoresizingMaskIntoConstraints = false
// 添加约束
addConstraint(NSLayoutConstraint(item: pullDownImageView, attribute: .centerX, relatedBy: .equal, toItem: self, attribute: .centerX, multiplier: 1, constant: -35))
addConstraint(NSLayoutConstraint(item: pullDownImageView, attribute: .centerY, relatedBy: .equal, toItem: self, attribute: .centerY, multiplier: 1, constant: 0))
addConstraint(NSLayoutConstraint(item: messageLabel, attribute: .leading, relatedBy: .equal, toItem: pullDownImageView, attribute: .trailing, multiplier: 1, constant: 0))
addConstraint(NSLayoutConstraint(item: messageLabel, attribute: .centerY, relatedBy: .equal, toItem: pullDownImageView, attribute: .centerY, multiplier: 1, constant: 0))
addConstraint(NSLayoutConstraint(item: indicatorView, attribute: .centerX, relatedBy: .equal, toItem: pullDownImageView, attribute: .centerX, multiplier: 1, constant: 0))
addConstraint(NSLayoutConstraint(item: indicatorView, attribute: .centerY, relatedBy: .equal, toItem: pullDownImageView, attribute: .centerY, multiplier: 1, constant: 0))
}
// 获取父控件, 当前控件将要添加到那个父视图上面
override func willMove(toSuperview newSuperview: UIView?) {
print(newSuperview)
// 判断是否是可以滚动的控件
if let scrollView = newSuperview as? UIScrollView {
// 表示是 UIScrollView 的子类, 可以监听器滚动
// 可以使用 kvo 监听 contentOffSet 值得改变
// [.new, .old] 表示可以监听新值和旧值得改变
scrollView.addObserver(self, forKeyPath: "contentOffset", options: .new, context: nil)
// 记录刷新视图控件
currentScrollView = scrollView
}
}
// kvo监听方法
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
guard let scrollView = currentScrollView else {
return
}
// 代码执行到此,表示 scrollView 不为 nil
// 计算临界点
let maxY = -(scrollView.contentInset.top + RefreshControlHeight)
// 获取 y 轴偏移量
let contentOffSetY = scrollView.contentOffset.y
// 判断是否拖动
// 拖动情况下只有两种状态 .normal, pulling
if scrollView.isDragging {
// 表示在拖动 判断的核心
if contentOffSetY < maxY && myRefreshType == .normal {
myRefreshType = .pulling
print("pulling")
} else if contentOffSetY >= maxY && myRefreshType == .pulling {
myRefreshType = .normal
print("normal")
}
} else {
// 表示松手 , 只有 pulling 状态 才能进入正在刷新
if myRefreshType == .pulling {
myRefreshType = .refreshing
print("正在刷新")
}
}
}
// 结束刷新
func endRefreshing() {
myRefreshType = .normal
}
deinit {
// 移除 kvo
currentScrollView?.removeObserver(self, forKeyPath: "contentOffset")
}
}
使用
// 自定义下拉刷新控件
fileprivate lazy var refreshControl: RefreshControl = RefreshControl()
tableView.addSubview(refreshControl)
refreshControl.addTarget(self, action: #selector(更新数据的方法名), for: UIControlEvents.valueChanged)
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