Swift3.0学习实践-一个简单的画板(七色轨迹可撤销可清除带橡皮擦)
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写着玩儿的小程序，继续学习swift.运行效果＋代码＋知识点总结
运行效果：
代码:
Canvas类：画布，画图板状态管理、交互、处理手势class Canvas:UIView
//负责线条的生成、操作与管理
private let pathCreator:PathCreator
//是否处于擦除状态
private var isInErasering:Bool
//橡皮擦视图
private let eraserView:UIView
override init(frame: CGRect)
isInErasering = false
pathCreator = PathCreator()
eraserView = UIView.init()
eraserView.frame = CGRect(x: 0, y: 0, width: 10, height: 10)
eraserView.backgroundColor = UIColor.white
eraserView.alpha = 0
super.init(frame: frame)
self.backgroundColor = UIColor.black
self.addSubview(eraserView)
let revokeBut = UIButton(type: UIButtonType.system)
revokeBut.frame = CGRect(x: 20, y: 20, width: 80, height: 30)
revokeBut.setTitle("撤销", for: UIControlState.normal)
revokeBut.addTarget(self, action: #selector(revokeButClick), for: UIControlEvents.touchUpInside)
self.addSubview(revokeBut)
let cleanBut = UIButton(type: UIButtonType.system)
cleanBut.frame = CGRect(x: 110, y: 20, width: 80, height: 30)
cleanBut.setTitle("清空", for: UIControlState.normal)
cleanBut.addTarget(self, action: #selector(cleanButClick), for: UIControlEvents.touchUpInside)
self.addSubview(cleanBut)
let eraserBut = UIButton(type: UIButtonType.system)
eraserBut.frame = CGRect(x: 200, y: 20, width:80, height: 30)
eraserBut.setTitle("橡皮", for: UIControlState.normal)
eraserBut.setTitle("画笔", for: UIControlState.selected)
eraserBut.addTarget(self, action: #selector(eraserButClick(but:)), for: UIControlEvents.touchUpInside)
self.addSubview(eraserBut)
let ges = UIPanGestureRecognizer(target: self, action:#selector(handleGes(ges:)))
ges.maximumNumberOfTouches = 1
self.addGestureRecognizer(ges)
required public init?(coder aDecoder: NSCoder)
fatalError("init(coder:) has not been implemented")
override public func layoutSubviews()
@objc private func handleGes(ges:UIPanGestureRecognizer) -> Void
let point = ges.location(in: self)
switch ges.state
case UIGestureRecognizerState.began:
if isInErasering
//擦除状态,显示出橡皮擦
eraserView.alpha = 1
eraserView.center = point
//生成新的一笔
pathCreator.addNewPath(to: point,isEraser: isInErasering)
self.setNeedsDisplay()
case UIGestureRecognizerState.changed:
if isInErasering
//移动橡皮擦
eraserView.center = ges.location(in: self)
//更新当前笔画路径
pathCreator.addLineForCurrentPath(to: point,isEraser:isInErasering)
self.setNeedsDisplay()
case UIGestureRecognizerState.ended:
if isInErasering
//擦除状态,隐藏橡皮擦
eraserView.alpha = 0
eraserView.center = ges.location(in: self)
//更新当前笔画路径
pathCreator.addLineForCurrentPath(to: point,isEraser: isInErasering)
self.setNeedsDisplay()
case UIGestureRecognizerState.cancelled:
print("cancel")
case UIGestureRecognizerState.failed:
print("fail")
default:
return
override public func draw(_ rect: CGRect)
//画线
pathCreator.drawPaths()
@objc private func revokeButClick()->Void
//撤销操作
pathCreator.revoke()
self.setNeedsDisplay()
@objc private func cleanButClick()->Void
//清空操作
pathCreator.clean()
self.setNeedsDisplay()
@objc private func eraserButClick(but:UIButton)->Void
//切换画图与擦除状态
if but.isSelected
but.isSelected = false
isInErasering = false
else
but.isSelected = true
isInErasering = true
PathCreator:具体线条绘制、管理
//每条子线段信息
struct BezierInfo
let path:UIBezierPath//具体线段
let color:UIColor//线段对应颜色
init(path:UIBezierPath,color:UIColor)
self.path = path
self.color = color
class PathCreator
//所有笔画
private var paths:[NSMutableArray]?
//笔画内当前子线段
private var currentBezierPathInfo:BezierInfo?
//当前笔画的所有子线段
private var currentPath:NSMutableArray?
//当前笔画已经采集处理了几个触摸点
private var pointCountInOnePath = 0
static let colors = [UIColor.red,UIColor.orange,UIColor.yellow,UIColor.green,UIColor.blue,UIColor.gray,UIColor.purple]
init()
paths = []
//添加新笔画
func addNewPath(to:CGPoint,isEraser:Bool)->Void
//创建起始线段
let path = UIBezierPath()
path.lineWidth = 5
path.move(to: to)
path.lineJoinStyle = CGLineJoin.round
path.lineCapStyle = CGLineCap.round
if !isEraser
//绑定线段与颜色信息
currentBezierPathInfo = BezierInfo(path: path, color: PathCreator.colors[0])
else
//处于擦除模式，颜色与画板背景色相同
currentBezierPathInfo = BezierInfo(path: path, color: UIColor.black)
//新建一个笔画
currentPath = NSMutableArray.init()
//将起始线段加入当前笔画
currentPath!.add(currentBezierPathInfo)
pointCountInOnePath = 0
//将当前笔画加入笔画数组
paths!.append(currentPath!)
//添加新的点，更新当前笔画路径
func addLineForCurrentPath(to:CGPoint,isEraser:Bool) -> Void
pointCountInOnePath += 1//同一笔画内，每7个点换一次颜色
if pointCountInOnePath % 7 == 0//换颜色
if let currentBezierPathInfo = currentBezierPathInfo
//将当前点加入当前子线段,更新当前子线段路径
currentBezierPathInfo.path.addLine(to: to)
//生成新的子线段
let path = UIBezierPath()
path.lineWidth = 5
path.move(to: to)
path.lineJoinStyle = CGLineJoin.round
path.lineCapStyle = CGLineCap.round
if !isEraser
//给当前子线段设置下一个颜色
currentBezierPathInfo = BezierInfo(path: path, color: PathCreator.colors[currentPath!.count % 7])
else
//处于擦除模式，颜色与画板背景色相同
currentBezierPathInfo = BezierInfo(path: path, color: UIColor.black)
//将当前子线段加入当前笔画
currentPath!.add(currentBezierPathInfo)
else
if let currentBezierPathInfo = currentBezierPathInfo
//将当前点加入当前子线段,更新当前子线段路径
currentBezierPathInfo.path.addLine(to: to)
func drawPaths()->Void
//画线
let pathCount = paths!.count
for i in 0..<pathCount
//取出所有笔画
let onePath = paths![i]
let onePathCount = onePath.count
for j in 0..<onePathCount
//绘制每条笔画内每个子线段
let pathInfo = onePath.object(at: j) as! BezierInfo
pathInfo.color.set()
pathInfo.path.stroke()
func revoke()->Void
//移走上一笔画
if paths!.count > 0
paths!.removeLast()
func clean()->Void
//移走所有笔画
paths!.removeAll()
知识点总结:
1.结构体是值传递
一个基础概念，但开始使用时还是给忘了。数组[]在swift中是结构体(struct)实现，值传递。最开始把currentPath声明为了[],添加到paths[]中后，后续再去往currentPath中添加元素，paths中的对应的currentpath对象内容并未随之发生改变，后将currentPath改为了NSMutableArray(引用传递).2.selector、@objc、private
(纯)swift与oc采用了不同的运行机制,swift不再采用与oc一样的运行时(runtime)与消息分发机制，selector作为oc运行机制的产物，swift中也对其进行了保留与支持。
@objc修饰符的作用是将swift定义的类、方法等暴露给oc。
于是，下列selector中指定的方法，都要使用@objc进行修饰
cleanBut.addTarget(self, action: #selector(cleanButClick), for: UIControlEvents.touchUpInside)let ges = UIPanGestureRecognizer(target: self, action:#selector(handleGes(ges:)))因为Canvas类(->UIView->UIResponder->NSObject)继承自NSObject,所以其属性或方法(非private)都会被自动加上@objc修饰 但是因为我代码中的这几个selector指向的方法都声明为了private,所以还是需要手动去做@objc修饰(如果是非private的，可以不写@objc)
@objc private func handleGes(ges:UIPanGestureRecognizer) -> Void3.required的构造函数
required用于修饰构造方法，用于要求子类必需实现对应的构造方法 如果子类中没有实现任何构造方法，则不必去显式的实现父类要求的required构造方法；而当子类中有定义实现构造方法时，则必需显式的去实现父类要求的required构造方法，同时还要保留required修饰. 当实现一个类Canvas继承自UIView时，我们可以看到编译器强制要求我们实现构造方法public init?(coder aDecoder: NSCoder)public protocol NSCoding
public func encode(with aCoder: NSCoder)
public init?(coder aDecoder: NSCoder) // NS_DESIGNATED_INITIALIZER
因为在协议中规定的构造方法，不用显式进行requird修饰，实现协议的对应类默认必需要去实现协议中规定的构造方法，且加上requird修饰
4.as
let x:UInt16 = 100
let y:UInt8 = 10
//x + y会报错，不自动类型转换，更安全
let n = UInt8(x) + y/// Create an instance initialized to `value`.
public init(integerLiteral value: UInt8)var people:People?
let man:Man = Man()
people = man
print(people)//可选型变量
let beMan = people as! Man
print (beMan)//强制转化后beMan不是可选型var people:People?
let man:Man = Man()
people = man
print(people)//可选型变量
let beMan = people as! Man?
print (beMan)//强制转化后beMan为可选型以上是关于Swift3.0学习实践-一个简单的画板(七色轨迹可撤销可清除带橡皮擦)的主要内容，如果未能解决你的问题，请参考以下文章