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前言：这个系列的目的是为了提供一些思路，在Demo的过程中让读者学会一些自定义控件的思路，所以不适宜太复杂。当然，仅仅是抛砖引玉。这个控件我会上传Github，由于最近一直在搞IOT的应用，所以没时间把进行完善，有时间了我会把这个控件完善了，，让读者那去直接就可以用。 完善好了我会更新下博客
Demo效果，支持两种显示过程的方式，沿着border绘制一圈和frame逐渐填充。
思路
NSURLSessionDataTask下载图片 用Layer的方式展示下载的过程
接口设计 头文件源代码
#import <UIKit/UIKit.h>typedef NS_ENUM(NSUInteger, WCProgressType) {WCProgressTypeBorder,WCProgressTypeFrame,};typedef void(^WCCompeltionBlock)(UIImage * image,NSError *error);(nonatomic,getter=currentProgress,readonly)CGFloat progress;@property (nonatomic,strong) NSString * url;@property (nonatomic)WCProgressType type;-(void)resume;-(instancetype)initWithFrame:(CGRect)frame ImageURL:(NSString *)url Type:(WCProgressType)type;-(instancetype)initWithFrame:(CGRect)frame ImageURL:(NSString *)url Type:(WCProgressType)type ComepetionHander:(WCCompeltionBlock)block;@end
1.由于这个要支持两种类型，所以定义枚举代表分别为两种类型 2.定义block来给用户异步传递imageview加载完成的时间 3.只读属性progress获得当前下载的进度 4.url和type分别代表image的url和进度条的类型 5.提供两个API来初始化对象
实现
(strong,nonatomic)NSMutableData * buffer;@property (nonatomic)NSUInteger expectlength;@property (nonatomic,strong)CALayer * frameProgressLayer;@property (nonatomic,strong)CAShapeLayer * borderProgressLayer;@property (strong,nonatomic)NSURLSessionDataTask * dataTask;@property (strong,nonatomic) NSURLSession * session;@property (nonatomic,strong) WCCompeltionBlock completionBlock;@property (nonatomic,getter=currentProgress,readwrite)CGFloat progress;#pragma mark – property-(NSMutableData *)buffer{if (!_buffer) {_buffer = [[NSMutableData alloc] init];}return _buffer;}-(CALayer *)frameProgressLayer{if (!_frameProgressLayer) {_frameProgressLayer = [CALayer layer];_frameProgressLayer.backgroundColor = [UIColor lightGrayColor].CGColor;_frameProgressLayer.bounds = CGRectMake(0,0,0,CGRectGetHeight(self.frame));_frameProgressLayer.anchorPoint = CGPointMake(0,0);_frameProgressLayer.position = CGPointMake(0,0);}return _frameProgressLayer;}-(CAShapeLayer *)borderProgressLayer{if (!_borderProgressLayer) {_borderProgressLayer = [CAShapeLayer layer];_borderProgressLayer));_borderProgressLayer.anchorPoint = CGPointMake(0,0);_borderProgressLayer.position = CGPointMake(0,0);_borderProgressLayer.fillColor = [UIColor clearColor].CGColor;_borderProgressLayer.lineWidth = 3.0;_borderProgressLayer.path = [UIBezierPath bezierPathWithRoundedRect:_borderProgressLayer.bounds cornerRadius:10.0].CGPath;_borderProgressLayer.strokeColor = [UIColor blueColor].CGColor;_borderProgressLayer.strokeStart = 0.0;_borderProgressLayer.strokeEnd = 0.0;}return _borderProgressLayer;}-(CGPathRef)createPathWith:(CGPoint *)center Radius:(CGFloat)radius Progress:(CGFloat)progress{CGMutablePathRef mutablepath = CGPathCreateMutable();return mutablepath;}-(NSURLSession *)session{if (!_session) {_session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]delegate:selfdelegateQueue:[NSOperationQueue mainQueue]];}return _session;}-(void)setUrl:(NSString *)url{self.progress = 0;dataTaskWithURL:[NSURL URLWithString:url]];}#pragma mark – API-(instancetype)initWithFrame:(CGRect)frame ImageURL:(NSString *)url Type:(WCProgressType)type{if (self = [super initWithFrame:frame]) {self.url = url;self.type = type;self.progress = 0;}return self;}-(instancetype)initWithFrame:(CGRect)frame ImageURL:(NSString *)url Type:(WCProgressType)type ComepetionHander:(WCCompeltionBlock)block{if (self = [super initWithFrame:frame]) {self.url = url;self.completionBlock = block;self.type = type;self.progress = 0;}return self;}-(void)resume{[self.dataTask resume];switch (self.type) {case WCProgressTypeFrame:[];break;case WCProgressTypeBorder:[];break;default:break;}}#pragma mark – URLSessionDelegate-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler{NSHTTPURLResponse * httpresponse = (NSHTTPURLResponse *)response;self.expectlength = [httpresponse expectedContentLength];completionHandler(NSURLSessionResponseAllow);}-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data{[self.buffer appendData:data];/(double)self.expectlength;NSLog(@”%f”,self.progress);if (self.expectlength > 0) {switch (self.type) {case WCProgressTypeFrame:= CGRectMake(,CGRectGetHeight(self.frame));break;case WCProgressTypeBorder:= self.progress;break;default:break;}}}-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error{[self.frameProgressLayer removeFromSuperlayer];self.frameProgressLayer = nil;[self.borderProgressLayer removeFromSuperlayer];self.borderProgressLayer = nil;if (!error) {UIImage * image = [UIImage imageWithData:self.buffer];self.image = image;if (self.completionBlock) {self.completionBlock(image,error);}}else{self.completionBlock(nil,error);}[self clean];}-(void)clean{self.buffer = nil;[self.session invalidateAndCancel];self.session = nil;}@end
讲解 1.属性采用惰性初始化 2.用CAShape Layer的StrokeEnd属性来代表进度 3.用NSURLSessionDelegate和NSURLSessionDataDelegate来获取数据和进度。
是清晰的又是朦胧的，是一杯苦茶，最后却品出清雅之香。
