iOS 自定义Tab页

在iOS里面可以用UISegmentedControl控件来表示Tab页，但其样式难以修改，我们一般会自定义Tab页。

1. 自定义Tab页

在这里我们首先定义UKTabItemView用来显示其中的标签页。

// 标签页代理
@protocol UKTabItemViewDelegate <NSObject>

- (void)onTabItemViewSelected:(UKTabItemView *)tabItemView;

@end

@interface UKTabItemView : UIView

@property(nonatomic, weak) id<UKTabItemViewDelegate> delegate;

// 设置标签页标题
- (void)setText:(NSString *)text;
// 设置标签页状态
- (void)setSelected:(BOOL)selected;

@end

@interface UKTabItemView ()

@property(nonatomic, strong) UIButton *itemButton;
@property(nonatomic, strong) UIView *indicatorView;

@end

@implementation UKTabItemView

- (instancetype)init {
    
    
    self = [super init];
    if (self) {
    
    
        [self setupInitialUI];
    }
    return self;
}

- (void)setupInitialUI {
    
    
    [self addSubview:self.itemButton];
    [self.itemButton mas_makeConstraints:^(MASConstraintMaker *make) {
    
    
        make.left.right.top.bottom.equalTo(self);
    }];
    
    [self addSubview:self.indicatorView];
    [self.indicatorView mas_makeConstraints:^(MASConstraintMaker *make) {
    
    
        make.bottom.equalTo(self);
        make.height.equalTo(@2);
        make.centerX.equalTo(self);
        make.width.equalTo(@60);
    }];
}

- (void)setText:(NSString *)text {
    
    
    [self.itemButton setTitle:text forState:UIControlStateNormal];
}

- (void)setSelected:(BOOL)selected {
    
    
    [self.itemButton setSelected:selected];
    self.indicatorView.hidden = !selected;

    if (selected) {
    
    
        [self.itemButton.titleLabel setFont:[UIFont systemFontOfSize:17]];
    } else {
    
    
        [self.itemButton.titleLabel setFont:[UIFont systemFontOfSize:15]];
    }
}

- (UIButton *)itemButton {
    
    
    if (!_itemButton) {
    
    
        _itemButton = [[UIButton alloc] init];
        [_itemButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [_itemButton setTitleColor:[UIColor blueColor] forState:UIControlStateSelected];
        
        [_itemButton.titleLabel setFont:[UIFont systemFontOfSize:15]];
        
        [_itemButton addTarget:self action:@selector(onItemClick:) forControlEvents:UIControlEventTouchUpInside];
    }
    
    return _itemButton;
}

- (void)onItemClick:(UIButton *)sender {
    
    
    if (self.delegate) {
    
    
        [self.delegate onTabItemViewSelected:self];
    }
}

- (UIView *)indicatorView {
    
    
    if (!_indicatorView) {
    
    
        _indicatorView = [[UIView alloc] init];
        
        _indicatorView.layer.backgroundColor = [UIColor blueColor].CGColor;
        _indicatorView.layer.cornerRadius = 1;
        _indicatorView.layer.masksToBounds = YES;
        _indicatorView.hidden = YES;
    }
    return _indicatorView;
}

@end

自定义UKTabView，包含若干个UKTabItemView，选中的选项卡字体和颜色会有变化，下面的提示也会变亮。

@protocol UKTabViewDelegate <NSObject>

- (void)onTabViewSelected:(UKTabView *)tabView position:(NSInteger)position;

@end

@interface UKTabView : UIView

@property(nonatomic, weak) id<UKTabViewDelegate> delegate;

- (void)setItems:(NSArray<NSString *> *)items selection:(NSInteger)selection;
- (void)setSelection:(NSInteger)selection;

@end

@interface UKTabView() <UKTabItemViewDelegate>

@property(nonatomic, assign) NSInteger selection;
@property(nonatomic, strong) NSMutableArray<UKTabItemView *> *tabItemViews;

@end

@implementation UKTabView

- (instancetype)init {
    
    
    self = [super init];
    if (self) {
    
    
        [self setupInitialUI];
    }
    return self;
}

- (instancetype)initWithFrame:(CGRect)frame {
    
    
    self = [super initWithFrame:frame];
    if (self) {
    
    
        [self setupInitialUI];
    }
    return self;
}

- (void)setupInitialUI {
    
    
   _selection = -1;
    self.tabItemViews = [[NSMutableArray alloc] init];
}

- (void)setItems:(NSArray<NSString *> *)items selection:(NSInteger)selection {
    
    
    [self.tabItemViews removeAllObjects];
    
    UKTabItemView *lastItemView = nil;
    for (NSString *item in items) {
    
    
        UKTabItemView *tabItemView = [[UKTabItemView alloc] init];
        [tabItemView setText:item];
        [self addSubview:tabItemView];
        
        // 所有的选项卡都等分排列
        [tabItemView mas_makeConstraints:^(MASConstraintMaker *make) {
    
    
            if (lastItemView) {
    
    
                make.left.equalTo(lastItemView.mas_right);
            } else {
    
    
                make.left.equalTo(self);
            }
            make.top.bottom.equalTo(self);
            make.width.equalTo(self).multipliedBy(1.0/item.length);
        }];
        
        lastItemView = tabItemView;
        
        [self internalAddTabItemView:tabItemView];
    }
    
    [self setSelection:selection];
}

- (void)internalAddTabItemView:(UKTabItemView *)itemView {
    
    
    // 添加itemView，并用tag记录位置
    itemView.tag = self.tabItemViews.count;
    [self.tabItemViews addObject:itemView];
    
    itemView.delegate = self;
}

- (void)setSelection:(NSInteger)selection {
    
    
    if (selection >= 0) {
    
    
        if (selection != self.selection) {
    
    
            if (self.selection >= 0) {
    
    
                [self.tabItemViews[self.selection] setSelected:NO];
            }
            
            _selection = selection;
            [self.tabItemViews[self.selection] setSelected:YES];
        }
    }
}

#pragma mark - UKTabItemViewDelegate -
- (void)onTabItemViewSelected:(UKTabItemView *)tabItemView {
    
    
    [self setSelection:tabItemView.tag];
    
    [self.delegate onTabViewSelected:self position:tabItemView.tag];
}

@end

在UIViewController里面，我们定义一个UKTabView，并添加三个选项卡

UKTabView *tabView = [[UKTabView alloc] initWithFrame:CGRectMake(10, 100, 320, 50)]
[tabView setItems:@[@"选项1", @"选项2", @"选项3"] selection:0];

[self.view addSubview:self.tabView];

效果如下

2. 与UIScrollView的互动

一个Tab页往往下面会有互动的界面，比如说UIScrollView、UICollectionView等，这里我们以UIScrollView来举例说明。一般这里的互动有两种，一种是Tab选项卡被选中后UIScrollView跟着变化，另一种是UIScrollView滚动后Tab选项卡跟着变化。

我们先添加一个显示图片的UIScrollView，

UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(10, 170, 320, 150)];
scrollView.contentSize = CGSizeMake(320*3, 150);
scrollView.pagingEnabled = YES;
scrollView.showsHorizontalScrollIndicator = NO;
        
scrollView.delegate = self;
[self.view addSubview: scrollView];

for (int index = 1; index <= 3; index++) {
    
    
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(320 * (index - 1), 0, 320, 150)];
    imageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"switcher%d", index]];
    [scrollView addSubview:imageView];
}

添加UKTabView的代理，监听每次Tab选项卡变化

#pragma mark - UKTabViewDelegate -
- (void)onTabViewSelected:(UKTabView *)tabView position:(NSInteger)position {
    
    
    [self.scrollView setContentOffset:CGPointMake(320 * position, 0) animated:YES];
}

添加UIScrollView的代理，当UIScrollView的滚动结束时，修改Tab选项卡的状态

#pragma mark - UIScrollViewDelegate -
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    
    
    CGFloat width = scrollView.contentOffset.x;
    NSInteger page = width/320 + 0.5;

    [self.tabView setSelection:page];
}

效果如下

3. 动态添加Tab选项卡

动态添加UKTabItemView，我们需要修改前面所有UKTabItemView的间距

- (void)addItemView:(UKTabItemView *)itemView {
    
    
    NSInteger len = self.subviews.count;

    for (UIView *view in self.subviews) {
    
    
        [view mas_updateConstraints:^(MASConstraintMaker *make) {
    
    
            make.width.equalTo(self).multipliedBy(1.0/(len + 1));
        }];
    }

    [self addSubview:itemView];
    [itemView mas_makeConstraints:^(MASConstraintMaker *make) {
    
    
        if (len == 0) {
    
    
            make.left.equalTo(self);
        } else {
    
    
            make.left.equalTo(self.subviews[len - 1].mas_right);
        }
        make.top.bottom.equalTo(self);
        make.width.equalTo(self).multipliedBy(1.0/(len + 1));
    }];

    [self internalAddTabItemView:itemView];
}

4. 提示栏

在上面的例子里面，提示栏都是包含在UITabItemView里面的，有时候我们可能需要提示栏有动态移动的效果，那么我们就把提示栏在UKTabView中定义。

// 设置提示栏的宽度、高度和颜色等
- (void)setIndicatorWidth:(NSInteger)width height:(NSInteger)height radius:(NSInteger)radius color:(UIColor *)color {
    
    
    self.indicatorWidth = width;
    self.indicatorHeight = height;
    self.indicatorRadius = radius;
    self.indicatorColor = color;

    if (width > 0) {
    
    
        self.indicatorLayer.fillColor = self.indicatorColor.CGColor;
        [self.layer addSublayer:self.indicatorLayer];
    } else {
    
    
        [self.indicatorLayer removeFromSuperlayer];
    }
}

// 修改当前选项卡后，重新绘制提示栏
- (void)setSelection:(NSInteger)selection {
    
    
    if (selection >= 0) {
    
    
        if (selection != self.selection) {
    
    
            if (self.selection >= 0) {
    
    
                [self.tabItemViews[self.selection] setSelected:NO];
            }

            _selection = selection;
            [self.tabItemViews[self.selection] setSelected:YES];
        }
        [self drawIndicatorView];
    }
}

// ratio为偏移度
- (void)setSelection:(NSInteger)selection offsetRatio:(CGFloat)ratio {
    
    
    if (selection >= 0) {
    
    
        self.offsetRatio = ratio;
        
        [self setSelection:selection];
    }
}

// 绘制提示栏，我们利用CALayer的隐式动画来给提示栏添加动态效果
// 每次添加选项卡后，提示栏宽度都会被清空
// 提示栏宽度不能超过选项卡本身宽度
- (void)drawIndicatorView {
    
    
    if (self.indicatorWidth > 0 && self.frame.size.width > 0 && self.tabItemViews.count > 0) {
    
    
        CGFloat itemWidth = self.frame.size.width*1.0/self.tabItemViews.count;
        BOOL initialized = self.indicatorActualWidth != 0;

        CGFloat startX = itemWidth * self.selection + itemWidth * self.offsetRatio;

        if (!initialized) {
    
    
            self.indicatorActualWidth = self.indicatorWidth;

            if (itemWidth <= self.indicatorWidth) {
    
    
                self.indicatorActualWidth = itemWidth;
            }
        }

        if (self.indicatorActualWidth < itemWidth) {
    
    
            startX += (itemWidth - self.indicatorActualWidth) / 2;
        }

        // 绘制选项卡
        if (!initialized) {
    
    
            UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, self.indicatorActualWidth, self.indicatorHeight) cornerRadius:self.indicatorRadius];
            self.indicatorLayer.path = path.CGPath;
        }
        
        // 如果有偏移量，去除CALayer隐式动画
        BOOL anim = self.offsetRatio == 0;        
        if (!anim) {
    
    
            [CATransaction begin];
            [CATransaction setDisableActions:true];
        }

        self.indicatorLayer.frame = CGRectMake(startX, self.frame.size.height - self.indicatorHeight, self.indicatorActualWidth, self.indicatorHeight);

        if (!anim) {
    
    
            [CATransaction commit];
        }
    }
}

我们在scrollViewWillBeginDragging方法 里面区分UIScrollView的滚动是由手势触发的还是代码触发的。在scrollViewDidScroll方法里面，如果是手势触发的移动，状态栏按照比例跟着移动。

#pragma mark - UIScrollViewDelegate -
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    
    
    self.dragging = YES;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    
    
    if (self.dragging) {
    
    
        CGFloat width = scrollView.contentOffset.x;
        NSInteger page = width/320 + 0.5;

        [self.tabView setSelection:page offsetRatio:(width/320 - page)];
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    
    
    CGFloat width = scrollView.contentOffset.x;
    NSInteger page = width/320 + 0.5;

    [self.tabView setSelection:page];
    self.dragging = NO;
}

效果如下