简单的选择切换视图

简单的选择切换视图，自定义选择类目和默认类目。

SelectiveView.h

#import <UIKit/UIKit.h>

@protocol SelectiveViewDelegate <NSObject>
//此代理方法中可做数据切换等操作
- (void)selectiveTag:(NSInteger)selectiveTag;

@end

@interface SelectiveView : UIView
{
    //按钮个数
    NSInteger buttonCount;
    //选中的按钮
    UIButton *selectedButton;
    //滑动视图
    UIScrollView *containerView;
}

@property (nonatomic, assign) id<SelectiveViewDelegate>delegate;
//selectiveArray自定义选择类目数组，startTag默认类目
- (instancetype)initWithFrame:(CGRect)frame andArray:(NSArray *)selectiveArray andStartTag:(NSInteger)startTag;

@end

SelectiveView.m

#import "SelectiveView.h"

@implementation SelectiveView
@synthesize delegate;

- (instancetype)initWithFrame:(CGRect)frame andArray:(NSArray *)selectiveArray andStartTag:(NSInteger)startTag
{
    self = [super initWithFrame:frame];
    if (self)
    {
        buttonCount = selectiveArray.count;
        //滑动视图
        containerView = [[UIScrollView alloc] init];
        containerView.showsHorizontalScrollIndicator = NO;
        [self addSubview:containerView];
        //按钮的宽度
        CGFloat buttonW;
        if (buttonCount <5)
        {
            buttonW = frame.size.width/buttonCount;
            containerView.frame = CGRectMake(0, 0, frame.size.width, frame.size.height);
            containerView.contentSize = CGSizeMake(frame.size.width, frame.size.height);
        }
        else
        {
            buttonW = (frame.size.width-frame.size.height)/4;
            containerView.frame = CGRectMake(0, 0, frame.size.width, frame.size.height);
            containerView.contentSize = CGSizeMake(buttonW*selectiveArray.count, frame.size.height);
            [self drawCoverView];
        }
        for (int i=0; i < buttonCount; i++)
        {
            UIButton *selectButton = [[UIButton alloc] initWithFrame:CGRectMake(i*buttonW, 0, buttonW, frame.size.height)];
            selectButton.tag = 100+i;
            [selectButton setTitle:selectiveArray[i] forState:UIControlStateNormal];
            [selectButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
            [selectButton.titleLabel setFont:[UIFont systemFontOfSize:16]];
            [selectButton addTarget:self action:@selector(clickedSelectButton:) forControlEvents:UIControlEventTouchUpInside];
            [containerView addSubview:selectButton];
        }
        [self clickedSelectButton:(UIButton *)[containerView viewWithTag:100+startTag]];
    }
    return self;
}

- (void)clickedSelectButton:(UIButton *)sender
{
    UIButton *button = sender;
    if (button != selectedButton)
    {
        [selectedButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [selectedButton.titleLabel setFont:[UIFont systemFontOfSize:16]];
        [button setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
        [button.titleLabel setFont:[UIFont systemFontOfSize:19]];
        selectedButton = button;
        if (buttonCount >= 5)
        {
            if (button.center.x > self.frame.size.width/2)
            {
                [containerView setContentOffset:CGPointMake(button.center.x-self.frame.size.width/2, 0) animated:YES];
            }
            else
            {
                [containerView setContentOffset:CGPointMake(0, 0) animated:YES];
            }
        }
    }
    [self.delegate selectiveTag:button.tag-100];
}
//绘制透明渐变视图
- (void)drawCoverView
{
    CAGradientLayer *colorLayer = [CAGradientLayer layer];
    colorLayer.frame = (CGRect){CGPointZero, CGSizeMake(self.frame.size.height, self.frame.size.height)};
    colorLayer.position = CGPointMake(self.frame.size.width-self.frame.size.height/2, self.frame.size.height/2);
    [self.layer addSublayer:colorLayer];
    
    // 颜色分配
    colorLayer.colors = @[(__bridge id)[UIColor colorWithRed:255/255.0 green:255/255.0 blue:255/255.0 alpha:                      0.0].CGColor,
                          (__bridge id)[UIColor colorWithRed:255/255.0 green:255/255.0 blue:255/255.0 alpha:1.0].CGColor];
    // 颜色分割线
    colorLayer.locations  = @[@(0.0), @(0.8)];
    // 起始点
    colorLayer.startPoint = CGPointMake(0, 0);
    // 结束点
    colorLayer.endPoint   = CGPointMake(1, 0);
}
@end