如何在分段控制按钮中永久取消选择一个片段直到再次单击它

Question

我有一个包含4个选项的UISegmentedControl。当选项被选择后，其应该保持已选状态。当相同的选项再次被点击时，其应该取消选择。

如何实现这个功能？

- Pradeep Rajkumar

Answer 1

由于UISegmentedControl只有在选择未选中的段时才会发送操作，因此您需要子类化UISegmentedControl来对其触摸处理进行微小更改。我使用了这个类：

@implementation MBSegmentedControl

// this sends a value changed event even if we reselect the currently selected segment
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    NSInteger current = self.selectedSegmentIndex;
    [super touchesBegan:touches withEvent:event];
    if (current == self.selectedSegmentIndex) {
        [self sendActionsForControlEvents:UIControlEventValueChanged];
    }
}

@end

现在，即使分段已被选中，您也将获得“UIControlEventValueChanged”事件。只需将当前索引保存在变量中，并在操作中进行比较。如果两个索引匹配，则必须取消选择所触摸的分段。

// _selectedSegmentIndex is an instance variable of the view controller

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    _selectedSegmentIndex = self.segment.selectedSegmentIndex;
}

- (IBAction)segmentChanged:(UISegmentedControl *)sender {
    if (sender.selectedSegmentIndex == _selectedSegmentIndex) {
        NSLog(@"Segment %d deselected", sender.selectedSegmentIndex);
        sender.selectedSegmentIndex =  UISegmentedControlNoSegment;
        _selectedSegmentIndex = UISegmentedControlNoSegment;
    }
    else {
        NSLog(@"Segment %d selected", sender.selectedSegmentIndex);
        _selectedSegmentIndex = sender.selectedSegmentIndex;
    }
}

---

iOS 7改变了UISegmentedControl的触摸处理方式。现在，在touchesEnded:期间更改了selectedSegmentIndex。

因此，更新后的子类应该如下所示：

@implementation MBSegmentedControl

+ (BOOL)isIOS7 {
    static BOOL isIOS7 = NO;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSInteger deviceSystemMajorVersion = [[[[[UIDevice currentDevice] systemVersion] componentsSeparatedByString:@"."] objectAtIndex:0] integerValue];
        if (deviceSystemMajorVersion >= 7) {
            isIOS7 = YES;
        }
        else {
            isIOS7 = NO;
        }
    });
    return isIOS7;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    NSInteger previousSelectedSegmentIndex = self.selectedSegmentIndex;
    [super touchesBegan:touches withEvent:event];
    if (![[self class] isIOS7]) {
        // before iOS7 the segment is selected in touchesBegan
        if (previousSelectedSegmentIndex == self.selectedSegmentIndex) {
            // if the selectedSegmentIndex before the selection process is equal to the selectedSegmentIndex
            // after the selection process the superclass won't send a UIControlEventValueChanged event.
            // So we have to do this ourselves.
            [self sendActionsForControlEvents:UIControlEventValueChanged];
        }
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    NSInteger previousSelectedSegmentIndex = self.selectedSegmentIndex;
    [super touchesEnded:touches withEvent:event];
    if ([[self class] isIOS7]) {
        // on iOS7 the segment is selected in touchesEnded
        if (previousSelectedSegmentIndex == self.selectedSegmentIndex) {
            [self sendActionsForControlEvents:UIControlEventValueChanged];
        }
    }
}

@end

---

Swift 2.2版本修复了Grzegorz指出的问题。

class ReselectableSegmentedControl: UISegmentedControl {
    @IBInspectable var allowReselection: Bool = true

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let previousSelectedSegmentIndex = self.selectedSegmentIndex
        super.touchesEnded(touches, withEvent: event)
        if allowReselection && previousSelectedSegmentIndex == self.selectedSegmentIndex {
            if let touch = touches.first {
                let touchLocation = touch.locationInView(self)
                if CGRectContainsPoint(bounds, touchLocation) {
                    self.sendActionsForControlEvents(.ValueChanged)
                }
            }
        }
    }
}

Swift 3.0对此进行了修复，修复后的代码如下：

class MyDeselectableSegmentedControl: UISegmentedControl {
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        let previousIndex = selectedSegmentIndex

        super.touchesEnded(touches, with: event)

        if previousIndex == selectedSegmentIndex {
            let touchLocation = touches.first!.location(in: self)

            if bounds.contains(touchLocation) {
                sendActions(for: .valueChanged)
            }
        }
    }
}

- Matthias Bauch

---

这个答案在iOS7发布时又帮了我一次。我应该可以再次点赞它。 - Alyoshak

您可以通过在此子类中添加 self.selectedSegmentIndex = UISegmentedControlNoSegment; 在 [self sendActionsForControlEvents:UIControlEventValueChanged]; 之前来封装取消选择的代码。 - Mike Pollard

该解决方案的问题在于，当您开始触摸组件并将其拖动到组件外部以取消触摸时，它仍会取消选择该项。 - Grzegorz Krukowski

那是一个非常棒的解决方案！谢谢。 - Raheel Sadiq

Answer 2

这里有一个解决方案，可以解决当您尝试通过在UISegmentControl上开始点击并稍后完成在外部触摸时取消选择时仍然发生取消选择的问题。

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint locationPoint = [[touches anyObject] locationInView:self];
CGPoint viewPoint = [self convertPoint:locationPoint fromView:self];
if ([self pointInside:viewPoint withEvent:event]) {
    int oldValue = self.selectedSegmentIndex;
    [super touchesEnded:touches withEvent:event];
    if (oldValue == self.selectedSegmentIndex)
    {
        [super setSelectedSegmentIndex:UISegmentedControlNoSegment];
        [self sendActionsForControlEvents:UIControlEventValueChanged];
    }
}
}

- Grzegorz Krukowski

---

[self pointInside:withEvent] 使用分段控件的可见尺寸。如果我使用它并在内部触摸，然后在释放前稍微拖动到外部，它会使该片段呈浅蓝色，就像我的手指仍在按下，并且不发送事件。是否有一种方法可以知道控件的 hitTest 区域以查看点是否在其中？ - LavaSlider

Answer 3

您可以使用以下方法实现（感谢 Grzegorz的答案 和 Matthias的答案）：

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    NSInteger previousSelectedSegmentIndex = self.selectedSegmentIndex;

    [super touchesEnded:touches withEvent:event];

    CGPoint locationPoint = [[touches anyObject] locationInView:self];
    CGPoint viewPoint = [self convertPoint:locationPoint fromView:self];
    if ([self pointInside:viewPoint withEvent:event] && previousSelectedSegmentIndex == self.selectedSegmentIndex) {
        self.selectedSegmentIndex = UISegmentedControlNoSegment;
        [self sendActionsForControlEvents:UIControlEventValueChanged];
    }
}

我制作了一个开源（MIT许可证）的类STASegmentedControl（支持iOS 7+），其中包含了这个功能（以及更多功能）。

- Stunner

Answer 4

关于@Matthias Bauch发布的答案，针对Xcode 7.3中的Swift 2.2，我需要进行些许修改:

class ReselectableSegmentedControl: UISegmentedControl {
    @IBInspectable var allowReselection: Bool = true
    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        let previousSelectedSegmentIndex = self.selectedSegmentIndex
        super.touchesEnded(touches, withEvent: event)
        if allowReselection && previousSelectedSegmentIndex == self.selectedSegmentIndex {
            if let touch = touches.first {
                let touchLocation = touch.locationInView(self)
                if CGRectContainsPoint(bounds, touchLocation) {
                    self.sendActionsForControlEvents(.ValueChanged)
                }
            }
        }
    }
}

- Kushal Ashok

Answer 5

由@Kushal Ashok发布的Swift3.1版本

class ReselectableSegmentedControl: UISegmentedControl {
    @IBInspectable var allowReselection: Bool = true

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        let previousSelectedSegmentIndex = self.selectedSegmentIndex
        super.touchesEnded(touches, with: event)
        if allowReselection && previousSelectedSegmentIndex == self.selectedSegmentIndex {
            if let touch = touches.first {
                let touchLocation = touch.location(in: self)
                if bounds.contains(touchLocation) {
                    self.sendActions(for: .valueChanged)
                }
            }
        }
    }
}

- Talles Borges

Answer 6

这是一个与iOS版本无关的解决方案。它自己选择行为方式。

@interface CustomSegmentedControl : UISegmentedControl
@end




@implementation CustomSegmentedControl{


BOOL _touchBegan;
BOOL _reactOnTouchBegan;
}



- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    _touchBegan = YES;

    NSInteger previousSelectedSegmentIndex = self.selectedSegmentIndex;
    [super touchesBegan:touches withEvent:event];
    if (_reactOnTouchBegan) {
        // before iOS7 the segment is selected in touchesBegan
        if (previousSelectedSegmentIndex == self.selectedSegmentIndex) {
            [self sendActionsForControlEvents:UIControlEventValueChanged];
        }
    }
}


-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    _touchBegan = NO;

    NSInteger previousSelectedSegmentIndex = self.selectedSegmentIndex;
    [super touchesEnded:touches withEvent:event];
    if (!_reactOnTouchBegan) {
        CGPoint locationPoint = [[touches anyObject] locationInView:self];
        CGPoint viewPoint = [self convertPoint:locationPoint fromView:self];
        if ([self pointInside:viewPoint withEvent:event]) {
            // on iOS7 the segment is selected in touchesEnded
            if (previousSelectedSegmentIndex == self.selectedSegmentIndex) {
                [self sendActionsForControlEvents:UIControlEventValueChanged];
            }
        }
    }
}


- (void)sendActionsForControlEvents:(UIControlEvents)controlEvents {
    if(controlEvents == UIControlEventValueChanged){
        _reactOnTouchBegan = _touchBegan;
    }
    [super sendActionsForControlEvents:controlEvents];
}


@end

- EisenRatte

Answer 7

非常有帮助！谢谢！我想对我的项目事件有更多的控制，所以我改编了@Matthias的答案，发送了一个自定义的“值未改变”事件。我在GitHub上放了一个例子。

我还加入了@Grzegorz的修复，使其在用户将手指拖出分段控件时能够正常工作。

- Geoff Hom

Answer 8

关于@Stunner的问题，这是我为实现目标做出的贡献。我改变了一些东西，并添加了属性_previousSelectedSegmentIndex；在@Stunner的代码中，变量previousSelectedSegmentIndex是无用的：

@implementation STASegmentedControl
{
    NSInteger _previousSelectedSegmentIndex;
}

- (void)setSelectedSegmentIndex:(NSInteger)selectedSegmentIndex
{
    [super setSelectedSegmentIndex: selectedSegmentIndex];

    _previousSelectedSegmentIndex = self.selectedSegmentIndex;
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesEnded:touches withEvent:event];

    CGPoint locationPoint = [[touches anyObject] locationInView:self];
    CGPoint viewPoint = [self convertPoint:locationPoint fromView:self];
    if (self.toggleableSegments) { // toggle selected segment on/off
        if ([self pointInside:viewPoint withEvent:event] && _previousSelectedSegmentIndex == self.selectedSegmentIndex) {
            self.selectedSegmentIndex = UISegmentedControlNoSegment;
            [self sendActionsForControlEvents:UIControlEventValueChanged];
        }
    }
    _previousSelectedSegmentIndex = self.selectedSegmentIndex;
}

- Gio Cat