图一
分析：MJRefresh框架主要使用了分层的设计思想，基类和很多子类，每个类做什么都分工明确，所以也就使得可扩展性很强。
基类所负责的事情主要是：
- 开始刷新、结束刷新、并用KVO来进行监听
- prepare：来添加子view、修改属性
- placeSubViews：修改子view的frame
- setState：通过设置刷新状态来调用刷新方法
由于这些方法子类也会更改，所以将方法公开，让子类能够继承
注意1
在给父类写分类的时候由于，分类可以写属性的方法，但是无法写实例变量，所以用运行时的方法给scrollView增加一个实例变量，如下：
#import <UIKit/UIKit.h>
#import "EOCRefreshBaseHeader.h"
@interface UIScrollView (EOCRefresh)
@property(nonatomic, strong)EOCRefreshBaseHeader *eocHeader;
@end
#import "UIScrollView+EOCRefresh.h"
#import <objc/runtime.h>
@implementation UIScrollView (EOCRefresh)
const static char EOCHeaderKey = 'H';
- (void)setEocHeader:(EOCRefreshBaseHeader *)eocHeader {
if (eocHeader != self.eocHeader) {
//删除旧的，添加新的header
[self.eocHeader removeFromSuperview];
[self insertSubview:eocHeader atIndex:0];
//分类可以写属性的方法，但是无法写实例变量，所以用运行时的方法给scrollView增加一个实例变量
objc_setAssociatedObject(self, &EOCHeaderKey, eocHeader, OBJC_ASSOCIATION_ASSIGN);
}
}
- (EOCRefreshBaseHeader *)eocHeader {
return objc_getAssociatedObject(self, &EOCHeaderKey);
}
@end
只有写了实例变量，我们才能
self.table.eocHeader = [EOCRefreshNormalHeader headerWithRefreshingBlock:^{
NSLog(@"header refreshing");
}];
这样的进行使用。
上面在将header加到tableView上面时，一共做了三件事情
- 创建header
- 加到superView
- 监听offset的改变，做出操作（kvo达成）
注意2
我们一般把控件的初始化方法写在initWithFrame方法中，因为调用init方法的时候，它会来调用initWithFrame。
- (instancetype)initWithFrame:(CGRect)frame {
//initWithFrame 你调用init方法的时候，它会来调用initWithFrame
if (self = [super initWithFrame:frame]) {
[self prepare];
self.state = EOCRefreshStateIdle;// 初始化默认状态,即闲置状态header是在屏幕外面的
}
return self;
}
比较简单的控件，我们可以使用autoresizingMask来适配，譬如这里self.autoresizingMask = UIViewAutoresizingFlexibleWidth;//autoSizing,self的宽度它会跟着superView一起改变
注意3
- 监听要放在基类的willMoveToSuperview方法中，并且当header被不同的tableView添加的时候，要移除原来的监听。当多个tableView创建多个header来监听。
- 这个时候还没有设置控件的frame，还可以在这里面设置它的一些固定的属性：宽和X值，而高度因头部控件和尾部控件的高度不一样，所以先不进行设置。
-(void)willMoveToSuperview:(UIView *)newSuperview {
//当self被添加到superView的时候，调用
if (newSuperview && [newSuperview isKindOfClass:[UIScrollView class]]) {
//非空，而且是UIScrollView
//同一个header被不同的table来添加的时候
[self.superview removeObserver:self forKeyPath:@"contentOffset"];
self.scrollView = (UIScrollView *)newSuperview;
self.originalScrollInsets = self.scrollView.contentInset;
//控件还没有设置frame
self.eoc_x = 0.f;
self.eoc_w = self.scrollView.eoc_w;
//footer和header都继承，这两者的高度是不一样
[newSuperview addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:nil];
}
}
注意4
当有子控件需要初始化时，要将父控件写为[[self alloc] init]，这样才会哪个子类调用就初始化成哪个子类。
+ (instancetype)headerWithRefreshingBlock:(eocRefreshingBlock)block {
EOCRefreshBaseHeader *header = [[self alloc] init];
header.refreshingBlock = block;
return header;
}
注意5
往下拉的时候yOffset是为负数。并且header它能够悬停：是通过contentInset来改变的，改变它的可见范围。
#import "EOCRefreshBaseHeader.h"
@implementation EOCRefreshBaseHeader
+ (instancetype)headerWithRefreshingBlock:(eocRefreshingBlock)block {
EOCRefreshBaseHeader *header = [[self alloc] init];
header.refreshingBlock = block;
return header;
}
- (void)prepare {
[super prepare];
//设置高度
self.eoc_h = 50.f;
// 不能再这里设置宽度，因为这个时候scrollView还为nil，因为alloc要比willMoveToSuperview先调用
// self.eoc_w = self.scrollView.eoc_w;
}
- (void)placeSubviews {
[super placeSubviews];
//设置y坐标,跟superView紧密相关 placeSubviews写在layoutSubviews中的，所以要在这里面设置Y值
self.eoc_y = -self.eoc_h-self.originalScrollInsets.top;
}
- (void)scrollOffsetDidChange:(NSDictionary *)change {
[super scrollOffsetDidChange:change];
// 我们的header它能够悬停：contentInset来改变的
//1、正在refreshing， 你滑动的时候，contentInset是改变的，因为你滑动到了临界点 进行刷新的时候，有EOCRefreshStateIdle和EOCRefreshStateRefreshing两种状态，两种状态的contentInset不同的
CGFloat yOffset = self.scrollView.eoc_offsetY;
CGFloat boundaryOffset = self.originalScrollInsets.top+self.eoc_h; // 临界值
CGFloat pullingPercent = -yOffset/boundaryOffset;
if (self.state == EOCRefreshStateRefreshing) {
self.alpha = 1.f; //如果不写它的话，刷新的情况下，alpha值会渐变的，实际效果是在refresh状态下不渐变
//往下拉的时候，yOffset是为负的，下拉的距离大于临界值就是刷新，InsetTop为临界值，不然就是下拉的距离
CGFloat finalInsetTop = (-yOffset > boundaryOffset)?boundaryOffset:-yOffset;
self.scrollView.eoc_insetT = finalInsetTop;
}
if (self.scrollView.dragging) { //正在滑动
self.alpha = pullingPercent; // 往下拉的时候，颜色渐变
if (self.state == EOCRefreshStateIdle && -yOffset > boundaryOffset) {
//处于闲置状态、而且大于边界值
self.state = EOCRefreshStatePulling; //设置为正在拉的状态
} else if (self.state == EOCRefreshStatePulling && -yOffset < boundaryOffset) {
self.state = EOCRefreshStateIdle; // 设置为闲置状态
}
} else { //松手了
if (self.state == EOCRefreshStatePulling) {
self.state = EOCRefreshStateRefreshing; // 设置为刷新状态
} else if (pullingPercent < 1) {
self.alpha = pullingPercent; // 小于1，即还没有到刷新状态的时候，header回去的时候也是渐变
}
}
}
- (void)setState:(EOCRefreshState)state {
[super setState:state];
if (state == EOCRefreshStateRefreshing) {
[UIView animateWithDuration:0.4f animations:^{
self.scrollView.eoc_insetT = self.originalScrollInsets.top+self.eoc_h;
//因为弹簧效果，当往下拉，松手后往上弹得时候，会使有yOffset小于临界值，从而调用上面的 CGFloat finalInsetTop = (-yOffset > boundaryOffset)?boundaryOffset:-yOffset; self.scrollView.eoc_insetT = finalInsetTop; 这句代码使header被隐藏了一部分，所以要加上下面这句代码
self.scrollView.eoc_offsetY = -(self.originalScrollInsets.top+self.eoc_h);
}];
//刷新block
[self beginRefresh];
} else if (state == EOCRefreshStateIdle) {
[UIView animateWithDuration:0.4f animations:^{
self.scrollView.contentInset = self.originalScrollInsets;
}];
}
}
@end
注意6
访问bundle中的image资源方法
_arrowImageView =
[[UIImageView alloc] initWithImage:[UIImage imageWithContentsOfFile:[[NSBundle bundleWithPath:[[NSBundle bundleForClass:[EOCRefreshNormalHeader class]] pathForResource:@"MJRefresh" ofType:@"bundle"]] pathForResource:@"arrow@2x" ofType:@"png"]]];
从MJRefresh.bundle中获取图片到EOCRefreshNormalHeader类中
注意7
如果一个控件经常用到，而且属性都一样，可以写成它的分类，并且放在基类里面， 如下面的label：
#import <UIKit/UIKit.h>
@interface EOCRefreshBaseView : UIView
typedef NS_ENUM(NSInteger, EOCRefreshState) {
EOCRefreshStateIdle = 1, //闲置状态
EOCRefreshStatePulling, //释放就刷新的状态
EOCRefreshStateRefreshing, //正在刷新状态
};
typedef void (^eocRefreshingBlock)();
//刷新数据的block
@property(nonatomic, strong)eocRefreshingBlock refreshingBlock;
@property(nonatomic, strong)UIScrollView *scrollView;
@property(nonatomic, assign)UIEdgeInsets originalScrollInsets;
@property(nonatomic, assign)EOCRefreshState state;
- (void)prepare; // 来添加子view、修改属性
- (void)placeSubviews; // 修改子view的frame
- (void)endRefresh; //结束刷新
- (void)beginRefresh; //开始刷新
- (void)scrollOffsetDidChange:(NSDictionary *)change;
@end
@interface UILabel (EOCLabel)
+ (instancetype)eocLabel;
- (CGFloat)textWidth;
@end
#import "EOCRefreshBaseView.h"
@interface EOCRefreshBaseView ()
@end
@implementation EOCRefreshBaseView
//head加进来：创建header、加到superView、监听offset的改变，做出操作（kvo达成）
-(instancetype)initWithFrame:(CGRect)frame {
//initWithFrame 你调用init方法的时候，它会来调用initWithFrame
if (self = [super initWithFrame:frame]) {
[self prepare];
self.state = EOCRefreshStateIdle; // 初始化默认状态,即闲置状态header是在屏幕外面的
}
return self;
}
-(void)prepare {
self.backgroundColor = [UIColor redColor];
self.autoresizingMask = UIViewAutoresizingFlexibleWidth;//autoSizing,self的宽度它会跟着superView一起改变
}
-(void)layoutSubviews {
[super layoutSubviews];
//修改子view的frame
[self placeSubviews];
}
-(void)placeSubviews {}
-(void)willMoveToSuperview:(UIView *)newSuperview {
//当self被添加到superView的时候，调用
if (newSuperview && [newSuperview isKindOfClass:[UIScrollView class]]) {
//非空，而且是UIScrollView
//同一个header被不同的table来添加的时候
[self.superview removeObserver:self forKeyPath:@"contentOffset"];
self.scrollView = (UIScrollView *)newSuperview;
self.originalScrollInsets = self.scrollView.contentInset;
//控件还没有设置frame
self.eoc_x = 0.f;
self.eoc_w = self.scrollView.eoc_w;
//footer和header都继承，这两者的高度是不一样
[newSuperview addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:nil];
}
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
if ([keyPath isEqualToString:@"contentOffset"]) {
[self scrollOffsetDidChange:change];
}
}
-(void)scrollOffsetDidChange:(NSDictionary *)change {}
-(void)setState:(EOCRefreshState)state {
_state = state;
}
-(void)endRefresh {
//把当前的时间存起来
[[NSUserDefaults standardUserDefaults]setObject:[NSDate date] forKey:@"lastUpdateDate"];
self.state = EOCRefreshStateIdle;
}
-(void)beginRefresh {
if (_refreshingBlock) {
_refreshingBlock();
}
}
@end
@implementation UILabel (EOCLabel)
+ (instancetype)eocLabel {
UILabel *label = [[UILabel alloc] init];
label.font = [UIFont systemFontOfSize:14.f];
label.backgroundColor = [UIColor clearColor];
label.textColor = [UIColor blueColor];
label.autoresizingMask = UIViewAutoresizingFlexibleWidth;
label.textAlignment = NSTextAlignmentCenter;
return label;
}
- (CGFloat)textWidth {
NSString *text = self.text;
UIFont *font = self.font;
CGSize textSize = [text sizeWithAttributes:@{NSFontAttributeName:font}];
return textSize.width;
}
@end
注意8
箭头旋转的时候，如果要实现顺时针旋转下来，逆时针旋转回去，需要将其中一个设置为CGAffineTransformMakeRotation(0.00001-M_PI)，用0.00001减去M_PI，因为旋转的时候遵循下面的三点
- 基本按照最短路径来，如果顺时针、逆时针角度一样的，按顺时针来
- CGAffineTransformMakeRotation会根据最初始的值来计算角度
- 角度为正，顺时针；角度为负，逆时针
所以当用0.00001减去M_PI的时候，那么来的路径变短了，所以就原路返回了
- (void)setState:(EOCRefreshState)state {
[super setState:state];
//1、刷新的时候，箭头要隐藏，loadview显示； 2、pulling的时候，箭头的方向改变
if (state == EOCRefreshStateIdle) {
[UIView animateWithDuration:0.4f animations:^{
self.loadView.alpha = 1.f;
_arrowImageView.transform = CGAffineTransformIdentity;
} completion:^(BOOL finished) {
// self.loadView.hidden = YES;
self.loadView.alpha = 0.f;
[self.loadView stopAnimating];
_arrowImageView.alpha = 1.f;
}];
} else if (state == EOCRefreshStatePulling) {
[UIView animateWithDuration:0.4f animations:^{
_arrowImageView.transform = CGAffineTransformMakeRotation(0.0001-M_PI);
}];
} else if (state == EOCRefreshStateRefreshing) {
_arrowImageView.alpha = 0.f;
// _loadView.hidden = NO;
_loadView.alpha = 0.f;
[_loadView startAnimating];
}
}
附注：
在iOS11过后，我们需要的contentInset的上下左右都要减去安全边距。
如下：
#import <UIKit/UIKit.h>
@interface UIScrollView (EOCExtention)
@property (readonly, nonatomic) UIEdgeInsets eoc_inset;
@property (assign, nonatomic) CGFloat eoc_insetT;
@property (assign, nonatomic) CGFloat eoc_insetB;
@property (assign, nonatomic) CGFloat eoc_insetL;
@property (assign, nonatomic) CGFloat eoc_insetR;
@property (assign, nonatomic) CGFloat eoc_offsetX;
@property (assign, nonatomic) CGFloat eoc_offsetY;
@property (assign, nonatomic) CGFloat eoc_contentW;
@property (assign, nonatomic) CGFloat eoc_contentH;
@end
#import "UIScrollView+EOCExtention.h"
@implementation UIScrollView (EOCExtention)
- (UIEdgeInsets)eoc_inset {
UIEdgeInsets insets = self.contentInset;
if (@available(iOS 11, *)) {
// https://www.jianshu.com/p/4f60d45097f0
insets = self.adjustedContentInset;
}
return insets;
}
- (void)setEoc_insetT:(CGFloat)eoc_insetT
{
//右边是不是等于adjustContentInsets：safeAreaInset+contentInset
UIEdgeInsets inset = self.contentInset;
inset.top = eoc_insetT;
if (@available(iOS 11, *)) {
inset.top -= self.safeAreaInsets.top;
}
self.contentInset = inset;
}
- (CGFloat)eoc_insetT
{
return self.eoc_inset.top;
}
- (void)setEoc_insetB:(CGFloat)eoc_insetB
{
UIEdgeInsets inset = self.contentInset;
inset.bottom = eoc_insetB;
if (@available(iOS 11, *)) {
inset.bottom -= self.safeAreaInsets.bottom;
}
self.contentInset = inset;
}
- (CGFloat)eoc_insetB
{
return self.eoc_inset.bottom;
}
- (void)setEoc_insetL:(CGFloat)eoc_insetL
{
UIEdgeInsets inset = self.contentInset;
inset.left = eoc_insetL;
if (@available(iOS 11, *)) {
inset.left -= self.safeAreaInsets.left;
}
self.contentInset = inset;
}
- (CGFloat)eoc_insetL
{
return self.eoc_inset.left;
}
- (void)setEoc_insetR:(CGFloat)eoc_insetR
{
UIEdgeInsets inset = self.contentInset;
inset.right = eoc_insetR;
if (@available(iOS 11, *)) {
inset.right -= self.safeAreaInsets.right;
}
self.contentInset = inset;
}
- (CGFloat)eoc_insetR
{
return self.eoc_inset.right;
}
- (void)setEoc_offsetX:(CGFloat)eoc_offsetX
{
CGPoint offset = self.contentOffset;
offset.x = eoc_offsetX;
self.contentOffset = offset;
}
- (CGFloat)eoc_offsetX
{
return self.contentOffset.x;
}
- (void)setEoc_offsetY:(CGFloat)eoc_offsetY
{
CGPoint offset = self.contentOffset;
offset.y = eoc_offsetY;
self.contentOffset = offset;
}
- (CGFloat)eoc_offsetY
{
return self.contentOffset.y;
}
- (void)setEoc_contentW:(CGFloat)eoc_contentW
{
CGSize size = self.contentSize;
size.width = eoc_contentW;
self.contentSize = size;
}
- (CGFloat)eoc_contentW
{
return self.contentSize.width;
}
- (void)setEoc_contentH:(CGFloat)eoc_contentH
{
CGSize size = self.contentSize;
size.height = eoc_contentH;
self.contentSize = size;
}
- (CGFloat)eoc_contentH
{
return self.contentSize.height;
}
@end
