为什么使用 UISegmentedControl 时 UIImageView 不隐藏？

Question

我有一个 UISegmentedControl，其中第一个控件将在 UITextView 中显示文本，而第二个控件将显示可滚动的 UIImageView。

在初始启动时，如果我切换到第二个控件，图像显示并切换回第一个控件，图像消失并显示 UITextView。

但是，当我第二次切换到第二个控件并切换回第一个控件时，图像仍然存在，我无法再显示 UITextView。

我的代码将图像隐藏在第一个控件中，文本显示在第二个控件中，反之亦然。

为什么第一次可以正常工作，但第二次切换控件时却不能正常工作？

我做错了什么？

谢谢

-(void)viewDidLoad
{
self.scrollView.delegate = self;

    self.textView.text = @"THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST.";

    self.textView.hidden = NO;
}

-(void)setScroller
{
    CGSize scrollableSize = CGSizeMake(self.view.frame.size.width, self.view.frame.size.height);
    [self.scrollView setContentSize:scrollableSize];

    self.imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"test.png"] ];
    self.imageView.frame = CGRectMake(0, 0, self.scrollView.frame.size.width, self.view.frame.size.height);

    self.scrollView.backgroundColor = [UIColor blackColor];
    self.scrollView.minimumZoomScale = 1.0  ;
    self.scrollView.maximumZoomScale = self.imageView.image.size.width / self.scrollView.frame.size.width;
    //self.scrollView.zoomScale = 1.0;
    [self.scrollView addSubview:self.imageView];
}

-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return self.imageView;
}

- (IBAction)segmentedControl:(UISegmentedControl *)sender
{
    if (self.segmentedControl.selectedSegmentIndex == 0)
    {
        // Display apppropriate info for About
        self.imageView.hidden = YES;
        self.textView.hidden = NO;
    }
    else
    {
        self.imageView.hidden = NO;
        self.textView.hidden = YES;

        [self setScroller];
    }
}

Answer 1

您应该从- (IBAction)segmentedControl:(UISegmentedControl *)sender 方法中删除[self setScroller];，并将其放入-(void)viewDidLoad。每次切换到第二段时，您都会调用[self setScroller];。

您的代码应如下所示：

-(void)viewDidLoad
{
    [super viewDidLoad];
    self.scrollView.delegate = self;
    [self setupScroller];
}

-(void)setupScroller
{
    // Set contentSize
    CGSize scrollableSize = CGSizeMake(self.view.frame.size.width, self.view.frame.size.height);
    self.scrollView.contentSize = scrollableSize;

    // Add textView
    self.textView.text = @"THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST.";
    self.textView.hidden = NO;

    // Add ImageView
    self.imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"test.png"]];
    self.imageView.frame = CGRectMake(0, 0, self.scrollView.frame.size.width, self.view.frame.size.height);
    self.imageView.hidden = YES;
    [self.scrollView addSubview:self.imageView];

    // Configure Zoom Scales and backgroundColor
    self.scrollView.backgroundColor = [UIColor blackColor];
    self.scrollView.minimumZoomScale = 1.0  ;
    self.scrollView.maximumZoomScale = self.imageView.image.size.width / self.scrollView.frame.size.width;
}

-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return self.imageView;
}

- (IBAction)segmentedControl:(UISegmentedControl *)sender
{
    if (self.segmentedControl.selectedSegmentIndex == 0)
    {
        // Display appropriate info for About
        self.imageView.hidden = YES;
        self.textView.hidden = NO;
    }
    else
    {
        self.imageView.hidden = NO;
        self.textView.hidden = YES;
    }
}

Answer 2

您的问题可能是您创建了很多“imageView”实例 为了解决您的问题，我建议：

    -(void)setScroller
    {
        CGSize scrollableSize = CGSizeMake(self.view.frame.size.width, self.view.frame.size.height);
        [self.scrollView setContentSize:scrollableSize];


        if(self.imageView == nil) {
        self.imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"test.png"]];

    [self.scrollView addSubview:self.imageView];
        }

self.imageView.frame = CGRectMake(0, 0, self.scrollView.frame.size.width, self.view.frame.size.height);

self.scrollView.backgroundColor = [UIColor blackColor];
        self.scrollView.minimumZoomScale = 1.0  ;
        self.scrollView.maximumZoomScale = self.imageView.image.size.width / self.scrollView.frame.size.width;
        //self.scrollView.zoomScale = 1.0;


        [self.imageView setNeedsDisplay];

        [self.imageView setImage:[UIImage imageNamed: @"test.png"]];
    }

我只把 self.imageView 的 Alloc + addSubView 放到了 if 中， 其余的都在外面，

现在可以了