LoadMoreControl like UIRefreshControl

LoadMoreControl.swift

//
//  LoadMoreControl.swift
//  GuilinLegal
//
//  Created by Haizhen Lee on 15/6/19.
//  Copyright (c) 2015年 banxi1988. All rights reserved.
//

import UIKit

final class LoadMoreControl: UIControl{
    enum LoadMoreState:Int{
        case Pulling
        case Pulled
        case Canceled
        case Loading
        case Loaded
        case LoadFailed
        
        var tipLabel:String{
            if self == .Pulling || self == .Canceled{
                return "下拉显示下20条"
            }else if self == .Pulled{
                return "释放显示下20条"
            }else if self == .Loading{
                return "正在加载..."
            }else if self == .Loaded{
                return "加载完成"
            }else if self == .LoadFailed{
                return "加载失败"
            }
            return ""
        }
    }
    
    private var loadMoreState = LoadMoreState.Canceled
    
    let titleLabel  = UILabel(frame: CGRectZero)
    private let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .WhiteLarge)
    init() {
        super.init(frame: CGRect(x: 0, y: 0, width: 320, height: 44))
        addSubview(titleLabel)
        addSubview(activityIndicator)
        titleLabel.setTranslatesAutoresizingMaskIntoConstraints(false)
        titleLabel.pinCenterY()
        titleLabel.pinCenterX()
        titleLabel.textColor = UIColor(white: 0.3, alpha: 1.0)
        titleLabel.font = UIFont.systemFontOfSize(14)
        
        activityIndicator.pinTrailingToSibing(titleLabel)
        activityIndicator.pinCenterY()
        activityIndicator.hidden = true
        
        
    }
    


    private func transitionToState(loadMoreState:LoadMoreState){
        self.loadMoreState = loadMoreState
        activityIndicator.hidden = loadMoreState != .Loading
        titleLabel.text = loadMoreState.tipLabel
    }
    
    var isPulling: Bool{ return loadMoreState == .Pulling }
    var isPulled: Bool{ return loadMoreState == .Pulled }
    var isCanceled: Bool{ return loadMoreState == .Canceled }
    var isLoading: Bool{ return loadMoreState == .Loading }
   
    func startPull(){
       transitionToState(.Pulling)
    }
    
    
    func pulled(){
        transitionToState(.Pulled)
    }
    
    
    func canceled(){
        transitionToState(.Canceled)
    }
    
    func startLoad(){
        transitionToState(.Loading)
        sendActionsForControlEvents(UIControlEvents.ValueChanged)
    }
    
    func loaded(){
        transitionToState(.Loaded)
    }
    
    func loadFailed(){
        transitionToState(.LoadFailed)
    }
    
    
    required init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

ScrollViewDelegateHook.swift

  override func scrollViewWillBeginDragging(scrollView: UIScrollView) {
        NSLog("\(__FUNCTION__) contentSize=\(scrollView.contentSize), frame=\(scrollView.frame) overflowY=\(scrollView.overflowY)")
    }
    
    override func scrollViewDidScroll(scrollView: UIScrollView) {
        let contentOffset = scrollView.contentOffset
        let overflowY = scrollView.frame.height + contentOffset.y - scrollView.contentSize.height
        NSLog("\(__FUNCTION__) contentoffset=\(contentOffset) overflowY=\(overflowY)")
        if !loadMoreControl.isLoading{
            if scrollView.isPulledUp && !loadMoreControl.isCanceled {
                if !loadMoreControl.isPulled{
                   loadMoreControl.pulled()
                    NSLog("startPull")
                }
                // overflowY 有两次达到此状态,一些上上拉,一次是加弹,所以需要判断一下
            }else if scrollView.isPullingUp{
                if !loadMoreControl.isPulling{
                    NSLog("startPull")
                    loadMoreControl.startPull()
                }
            }
        }
    }
    
   
    override func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        NSLog("\(__FUNCTION__) velocity=\(velocity) targetContentOffset=\(targetContentOffset.memory)")
    }
    
    
    override func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        NSLog("\(__FUNCTION__) willDecelerate?=\(decelerate)")
        if !loadMoreControl.isLoading{
            if scrollView.isPulledUp{
                NSLog("startLoad")
                loadMoreControl.startLoad()
            }else{
                NSLog("canceled")
                loadMoreControl.canceled()
            }
        }
    }
    
    override func scrollViewWillBeginDecelerating(scrollView: UIScrollView) {
        NSLog("\(__FUNCTION__)")
    }
    
    override func scrollViewDidEndDecelerating(scrollView: UIScrollView) {
        NSLog("\(__FUNCTION__) offset=\(scrollView.contentOffset)")
    }