TMMuiLazyScrollView的使用详解

LazyScrollView 是一个高性能的 scrollView 重用布局框架, 实现了视图的重用和自动加载。

使用时候的核心代码：

// This protocol represents the data model object.@class TMMuiLazyScrollView;@protocol TMMuiLazyScrollViewDataSource <NSObject>@required- (NSUInteger)numberOfItemInScrollView:(nonnull TMMuiLazyScrollView *)scrollView; - (nonnull TMMuiRectModel *)scrollView:(nonnull TMMuiLazyScrollView *)scrollView                      rectModelAtIndex:(NSUInteger)index;- (nullable UIView *)scrollView:(nonnull TMMuiLazyScrollView *)scrollView itemByMuiID:(nonnull NSString *)muiID;@end

类似UITableView的用法，最大的区别就是在布局前计算出每个view的位置frame：

1、获取要展示的个数

2、获取每个view的数据model

3、创建每个视图view

这里的model继承TMMuiRectModel，那么TMMuiRectModel又是怎样的呢？

/** * It is a view model that holding information of view. At least holding absoluteRect and muiID. */@interface TMMuiRectModel: NSObject// A rect that relative to the scroll view.@property (nonatomic, assign) CGRect absoluteRect;// A uniq string that identify a model.@property (nonatomic, copy, nonnull) NSString *muiID;@end

从这里可以看出，每个model必须赋值frame，所以这里需要在布局前计算出每个view的位置frame，还有一个参数muiID，它是View的唯一标识符。

对于创建的每个view，可以继承<TMMuiLazyScrollViewCellProtocol>，来监测view的生命周期

protocol  TMMuiLazyScrollViewCellProtocol<NSObject>@optional// if call dequeueReusableItemWithIdentifier to get a reuseable view,the same as "prepareForReuse" in UITableViewCell- (void)mui_prepareForReuse;// When view enter the visible area of LazyScrollView ，call this method.// First 'times' is 0- (void)mui_didEnterWithTimes:(NSUInteger)times;// When we need render the view, call this method.// The difference between this method and 'mui_didEnterWithTimes' is there is a buffer area in LazyScrollView(RenderBufferWindow), first we will call 'mui_afterGetView'.- (void)mui_afterGetView;@end

具体的实现代码如下：

////  ViewController.m//  Demo////  Created by 胡梦驰 on 2017/8/2.//  Copyright © 2017年 胡梦驰. All rights reserved.//#import "ViewController.h"#import "TMMuiLazyScrollView.h"@interface LazyScrollViewCustomView : UIView<TMMuiLazyScrollViewCellProtocol>@end@implementation LazyScrollViewCustomView//在即将被复用时调用，通常用于清空View内展示的数据。类似与UITableViewCell 的 prepareForReuse- (void)mui_prepareForReuse{    NSLog(@"- Prepare For Reuse -");}//进入屏幕LazyScroll可视范围内时执行，times是进入可视范围的次数，从0开始。重置times可以调用LazyScrollView的resetViewEnterTimes重置times- (void)mui_didEnterWithTimes:(NSUInteger)times{    NSLog(@"- Did Enter With Times -");}//LazyScroll获取到View后执行。也就是执行完- (UIView *)scrollView:(TMMuiLazyScrollView *)scrollView itemByMuiID:(NSString *)muiID方法获取到视图之后。- (void)mui_afterGetView{    NSLog(@"- AfterGetView -");}@end@interface ViewController ()<TMMuiLazyScrollViewDataSource>@property (nonatomic, strong) NSMutableArray *rectArray;@end#define WIDTH self.view.frame.size.width#define HEIGHT self.view.frame.size.height@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];        self.rectArray = [NSMutableArray array];    CGFloat height = 0;    //一行只放一个view    for(int i = 0; i < 2; i++){        CGRect frame = CGRectMake(16, 10+i*60, WIDTH-32, 50);        [self.rectArray addObject:[NSValue valueWithCGRect:frame]];    }    height += 120;        //一行放两个    for(int i = 0; i < 4; i++){        CGRect frame = CGRectMake(16+i%2*((WIDTH-42)/2+10), height+10+i/2*60, (WIDTH-42)/2, 50);        [self.rectArray addObject:[NSValue valueWithCGRect:frame]];    }    height+= 120;        //一行放三个    for(int i = 0; i < 6; i++){        CGRect frame = CGRectMake(16+i%3*((WIDTH-52)/3+10), height+10+i/3*60, (WIDTH-52)/3, 50);        [self.rectArray addObject:[NSValue valueWithCGRect:frame]];    }    height+= 120;        //创建scrollView    TMMuiLazyScrollView *scrollView = [[TMMuiLazyScrollView alloc] init];    scrollView.frame = CGRectMake(0, 20, WIDTH, HEIGHT-20);    scrollView.dataSource = self;    [self.view addSubview:scrollView];        //对scrollview的content大小设置，并加载reloadData    scrollView.contentSize = CGSizeMake(WIDTH, height);    [scrollView reloadData];}#pragma mark -- DataSource/Delegate- (NSUInteger)numberOfItemInScrollView:(TMMuiLazyScrollView *)scrollView{    return self.rectArray.count;}- (TMMuiRectModel*)scrollView:(TMMuiLazyScrollView *)scrollView rectModelAtIndex:(NSUInteger)index{    CGRect frame = [(NSValue*)self.rectArray[index] CGRectValue];    TMMuiRectModel *model = [[TMMuiRectModel alloc] init];    model.absoluteRect = frame;    model.muiID = [NSString stringWithFormat:@"%ld", index];    return model;}- (UIView*)scrollView:(TMMuiLazyScrollView *)scrollView itemByMuiID:(NSString *)muiID{    NSInteger index = muiID.integerValue;    CGRect frame = [(NSValue*)self.rectArray[index] CGRectValue];    static NSString *identify = @"hmc";    LazyScrollViewCustomView *view = (LazyScrollViewCustomView*)[scrollView dequeueReusableItemWithIdentifier:identify];    if(!view){        view = [[LazyScrollViewCustomView alloc] initWithFrame:frame reuseIdentifier:identify];        view.backgroundColor = [UIColor cyanColor];    }    view.frame = frame;    view.backgroundColor = [self randomColor];    //切记要把创建的view添加到scrollview中    [scrollView addSubview:view];    return view;}//随机颜色- (UIColor *)randomColor{    CGFloat hue = ( arc4random() % 256 / 256.0 ); //0.0 to 1.0    CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5; // 0.5 to 1.0,away from white    CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5; //0.5 to 1.0,away from black    return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];    }@end