圖一
分析：MJRefresh框架主要使用了分層的設(shè)計思想貌虾，基類和很多子類，每個類做什么都分工明確裙犹，所以也就使得可擴展性很強尽狠。
基類所負(fù)責(zé)的事情主要是：
- 開始刷新、結(jié)束刷新叶圃、并用KVO來進行監(jiān)聽
- prepare：來添加子view袄膏、修改屬性
- placeSubViews：修改子view的frame
- setState：通過設(shè)置刷新狀態(tài)來調(diào)用刷新方法
由于這些方法子類也會更改，所以將方法公開掺冠，讓子類能夠繼承
注意1
在給父類寫分類的時候由于沉馆，分類可以寫屬性的方法，但是無法寫實例變量德崭，所以用運行時的方法給scrollView增加一個實例變量斥黑，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) {
//刪除舊的，添加新的header
[self.eocHeader removeFromSuperview];
[self insertSubview:eocHeader atIndex:0];
//分類可以寫屬性的方法眉厨，但是無法寫實例變量锌奴，所以用運行時的方法給scrollView增加一個實例變量
objc_setAssociatedObject(self, &EOCHeaderKey, eocHeader, OBJC_ASSOCIATION_ASSIGN);
}
}
- (EOCRefreshBaseHeader *)eocHeader {
return objc_getAssociatedObject(self, &EOCHeaderKey);
}
@end
只有寫了實例變量，我們才能
self.table.eocHeader = [EOCRefreshNormalHeader headerWithRefreshingBlock:^{
NSLog(@"header refreshing");
}];
這樣的進行使用缺猛。
上面在將header加到tableView上面時缨叫，一共做了三件事情
- 創(chuàng)建header
- 加到superView
- 監(jiān)聽offset的改變，做出操作（kvo達(dá)成）
注意2
我們一般把控件的初始化方法寫在initWithFrame方法中荔燎，因為調(diào)用init方法的時候耻姥，它會來調(diào)用initWithFrame。
- (instancetype)initWithFrame:(CGRect)frame {
//initWithFrame 你調(diào)用init方法的時候有咨，它會來調(diào)用initWithFrame
if (self = [super initWithFrame:frame]) {
[self prepare];
self.state = EOCRefreshStateIdle;// 初始化默認(rèn)狀態(tài),即閑置狀態(tài)header是在屏幕外面的
}
return self;
}
比較簡單的控件琐簇，我們可以使用autoresizingMask來適配，譬如這里self.autoresizingMask = UIViewAutoresizingFlexibleWidth;//autoSizing,self的寬度它會跟著superView一起改變
注意3
- 監(jiān)聽要放在基類的willMoveToSuperview方法中，并且當(dāng)header被不同的tableView添加的時候婉商，要移除原來的監(jiān)聽似忧。當(dāng)多個tableView創(chuàng)建多個header來監(jiān)聽。
- 這個時候還沒有設(shè)置控件的frame丈秩，還可以在這里面設(shè)置它的一些固定的屬性：寬和X值盯捌，而高度因頭部控件和尾部控件的高度不一樣，所以先不進行設(shè)置蘑秽。
-(void)willMoveToSuperview:(UIView *)newSuperview {
//當(dāng)self被添加到superView的時候饺著，調(diào)用
if (newSuperview && [newSuperview isKindOfClass:[UIScrollView class]]) {
//非空，而且是UIScrollView
//同一個header被不同的table來添加的時候
[self.superview removeObserver:self forKeyPath:@"contentOffset"];
self.scrollView = (UIScrollView *)newSuperview;
self.originalScrollInsets = self.scrollView.contentInset;
//控件還沒有設(shè)置frame
self.eoc_x = 0.f;
self.eoc_w = self.scrollView.eoc_w;
//footer和header都繼承肠牲，這兩者的高度是不一樣
[newSuperview addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:nil];
}
}
注意4
當(dāng)有子控件需要初始化時幼衰，要將父控件寫為[[self alloc] init]，這樣才會哪個子類調(diào)用就初始化成哪個子類缀雳。
+ (instancetype)headerWithRefreshingBlock:(eocRefreshingBlock)block {
EOCRefreshBaseHeader *header = [[self alloc] init];
header.refreshingBlock = block;
return header;
}
注意5
往下拉的時候yOffset是為負(fù)數(shù)渡嚣。并且header它能夠懸停：是通過contentInset來改變的，改變它的可見范圍肥印。
#import "EOCRefreshBaseHeader.h"
@implementation EOCRefreshBaseHeader
+ (instancetype)headerWithRefreshingBlock:(eocRefreshingBlock)block {
EOCRefreshBaseHeader *header = [[self alloc] init];
header.refreshingBlock = block;
return header;
}
- (void)prepare {
[super prepare];
//設(shè)置高度
self.eoc_h = 50.f;
// 不能再這里設(shè)置寬度识椰，因為這個時候scrollView還為nil，因為alloc要比willMoveToSuperview先調(diào)用
// self.eoc_w = self.scrollView.eoc_w;
}
- (void)placeSubviews {
[super placeSubviews];
//設(shè)置y坐標(biāo),跟superView緊密相關(guān) placeSubviews寫在layoutSubviews中的竖独，所以要在這里面設(shè)置Y值
self.eoc_y = -self.eoc_h-self.originalScrollInsets.top;
}
- (void)scrollOffsetDidChange:(NSDictionary *)change {
[super scrollOffsetDidChange:change];
// 我們的header它能夠懸停：contentInset來改變的
//1裤唠、正在refreshing挤牛， 你滑動的時候莹痢，contentInset是改變的，因為你滑動到了臨界點 進行刷新的時候墓赴，有EOCRefreshStateIdle和EOCRefreshStateRefreshing兩種狀態(tài)竞膳，兩種狀態(tài)的contentInset不同的
CGFloat yOffset = self.scrollView.eoc_offsetY;
CGFloat boundaryOffset = self.originalScrollInsets.top+self.eoc_h; // 臨界值
CGFloat pullingPercent = -yOffset/boundaryOffset;
if (self.state == EOCRefreshStateRefreshing) {
self.alpha = 1.f; //如果不寫它的話，刷新的情況下诫硕，alpha值會漸變的坦辟，實際效果是在refresh狀態(tài)下不漸變
//往下拉的時候，yOffset是為負(fù)的章办，下拉的距離大于臨界值就是刷新锉走，InsetTop為臨界值，不然就是下拉的距離
CGFloat finalInsetTop = (-yOffset > boundaryOffset)?boundaryOffset:-yOffset;
self.scrollView.eoc_insetT = finalInsetTop;
}
if (self.scrollView.dragging) { //正在滑動
self.alpha = pullingPercent; // 往下拉的時候藕届，顏色漸變
if (self.state == EOCRefreshStateIdle && -yOffset > boundaryOffset) {
//處于閑置狀態(tài)挪蹭、而且大于邊界值
self.state = EOCRefreshStatePulling; //設(shè)置為正在拉的狀態(tài)
} else if (self.state == EOCRefreshStatePulling && -yOffset < boundaryOffset) {
self.state = EOCRefreshStateIdle; // 設(shè)置為閑置狀態(tài)
}
} else { //松手了
if (self.state == EOCRefreshStatePulling) {
self.state = EOCRefreshStateRefreshing; // 設(shè)置為刷新狀態(tài)
} else if (pullingPercent < 1) {
self.alpha = pullingPercent; // 小于1，即還沒有到刷新狀態(tài)的時候休偶，header回去的時候也是漸變
}
}
}
- (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;
//因為彈簧效果梁厉，當(dāng)往下拉，松手后往上彈得時候踏兜，會使有yOffset小于臨界值词顾，從而調(diào)用上面的 CGFloat finalInsetTop = (-yOffset > boundaryOffset)?boundaryOffset:-yOffset; self.scrollView.eoc_insetT = finalInsetTop; 這句代碼使header被隱藏了一部分八秃，所以要加上下面這句代碼
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
訪問bundle中的image資源方法
_arrowImageView =
[[UIImageView alloc] initWithImage:[UIImage imageWithContentsOfFile:[[NSBundle bundleWithPath:[[NSBundle bundleForClass:[EOCRefreshNormalHeader class]] pathForResource:@"MJRefresh" ofType:@"bundle"]] pathForResource:@"arrow@2x" ofType:@"png"]]];
從MJRefresh.bundle中獲取圖片到EOCRefreshNormalHeader類中
注意7
如果一個控件經(jīng)常用到，而且屬性都一樣肉盹，可以寫成它的分類昔驱，并且放在基類里面， 如下面的label：
#import <UIKit/UIKit.h>
@interface EOCRefreshBaseView : UIView
typedef NS_ENUM(NSInteger, EOCRefreshState) {
EOCRefreshStateIdle = 1, //閑置狀態(tài)
EOCRefreshStatePulling, //釋放就刷新的狀態(tài)
EOCRefreshStateRefreshing, //正在刷新狀態(tài)
};
typedef void (^eocRefreshingBlock)();
//刷新數(shù)據(jù)的block
@property(nonatomic, strong)eocRefreshingBlock refreshingBlock;
@property(nonatomic, strong)UIScrollView *scrollView;
@property(nonatomic, assign)UIEdgeInsets originalScrollInsets;
@property(nonatomic, assign)EOCRefreshState state;
- (void)prepare; // 來添加子view上忍、修改屬性
- (void)placeSubviews; // 修改子view的frame
- (void)endRefresh; //結(jié)束刷新
- (void)beginRefresh; //開始刷新
- (void)scrollOffsetDidChange:(NSDictionary *)change;
@end
@interface UILabel (EOCLabel)
+ (instancetype)eocLabel;
- (CGFloat)textWidth;
@end
#import "EOCRefreshBaseView.h"
@interface EOCRefreshBaseView ()
@end
@implementation EOCRefreshBaseView
//head加進來：創(chuàng)建header舍悯、加到superView、監(jiān)聽offset的改變睡雇，做出操作（kvo達(dá)成）
-(instancetype)initWithFrame:(CGRect)frame {
//initWithFrame 你調(diào)用init方法的時候萌衬，它會來調(diào)用initWithFrame
if (self = [super initWithFrame:frame]) {
[self prepare];
self.state = EOCRefreshStateIdle; // 初始化默認(rèn)狀態(tài),即閑置狀態(tài)header是在屏幕外面的
}
return self;
}
-(void)prepare {
self.backgroundColor = [UIColor redColor];
self.autoresizingMask = UIViewAutoresizingFlexibleWidth;//autoSizing,self的寬度它會跟著superView一起改變
}
-(void)layoutSubviews {
[super layoutSubviews];
//修改子view的frame
[self placeSubviews];
}
-(void)placeSubviews {}
-(void)willMoveToSuperview:(UIView *)newSuperview {
//當(dāng)self被添加到superView的時候，調(diào)用
if (newSuperview && [newSuperview isKindOfClass:[UIScrollView class]]) {
//非空它抱，而且是UIScrollView
//同一個header被不同的table來添加的時候
[self.superview removeObserver:self forKeyPath:@"contentOffset"];
self.scrollView = (UIScrollView *)newSuperview;
self.originalScrollInsets = self.scrollView.contentInset;
//控件還沒有設(shè)置frame
self.eoc_x = 0.f;
self.eoc_w = self.scrollView.eoc_w;
//footer和header都繼承秕豫，這兩者的高度是不一樣
[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 {
//把當(dāng)前的時間存起來
[[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
箭頭旋轉(zhuǎn)的時候，如果要實現(xiàn)順時針旋轉(zhuǎn)下來观蓄，逆時針旋轉(zhuǎn)回去混移，需要將其中一個設(shè)置為CGAffineTransformMakeRotation(0.00001-M_PI)，用0.00001減去M_PI侮穿，因為旋轉(zhuǎn)的時候遵循下面的三點
- 基本按照最短路徑來歌径，如果順時針、逆時針角度一樣的亲茅，按順時針來
- CGAffineTransformMakeRotation會根據(jù)最初始的值來計算角度
- 角度為正回铛，順時針；角度為負(fù)克锣，逆時針
所以當(dāng)用0.00001減去M_PI的時候茵肃，那么來的路徑變短了，所以就原路返回了
- (void)setState:(EOCRefreshState)state {
[super setState:state];
//1袭祟、刷新的時候验残，箭頭要隱藏，loadview顯示巾乳； 2您没、pulling的時候，箭頭的方向改變
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過后胆绊，我們需要的contentInset的上下左右都要減去安全邊距氨鹏。
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, *)) {
// http://www.reibang.com/p/4f60d45097f0
insets = self.adjustedContentInset;
}
return insets;
}
- (void)setEoc_insetT:(CGFloat)eoc_insetT
{
//右邊是不是等于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
