以编程方式滚动 UIScrollView

Question

I have a UIScrollView which has several views. When a user flicks their finger, the view scrolls to the right or left depending on the direction of the finger flick. Basically my code works in a way similar to the iPhone photo app. Now, is there a way that I can programmatically do the same thing so that I end up with a slideshow that runs on its own with a click of a button and a configurable pause between each scroll?

How do you really do slideshows with UIScrollView ?

Answer 1

You can scroll to some point in a scroll view with one of the following statements in Objective-C

[scrollView setContentOffset:CGPointMake(x, y) animated:YES];

or Swift

scrollView.setContentOffset(CGPoint(x: x, y: y), animated: true)

See the guide " Scrolling the Scroll View Content " from Apple as well .

To do slideshows with UIScrollView , you arrange all images in the scroll view, set up a repeated timer, then -setContentOffset:animated: when the timer fires.

But a more efficient approach is to use 2 image views and swap them using transitions or simply switching places when the timer fires. See iPhone Image slideshow for details.

Answer 2

If you want control over the duration and style of the animation, you can do:

[UIView animateWithDuration:2.0f delay:0 options:UIViewAnimationOptionCurveLinear animations:^{
    scrollView.contentOffset = CGPointMake(x, y);
} completion:NULL];

Adjust the duration ( 2.0f ) and options ( UIViewAnimationOptionCurveLinear ) to taste!

Answer 3

另一种方式是

scrollView.contentOffset = CGPointMake(x,y);

Answer 4

Swift 中的动画

scrollView.setContentOffset(CGPointMake(x, y), animated: true)

Answer 5

I'm amazed that this topic is 9 years old and the actual straightforward answer is not here!

What you're looking for is scrollRectToVisible(_:animated:) .

Example:

extension SignUpView: UITextFieldDelegate {
    func textFieldDidBeginEditing(_ textField: UITextField) {
        scrollView.scrollRectToVisible(textField.frame, animated: true)
    }
}

What it does is exactly what you need, and it's far better than hacky contentOffset

This method scrolls the content view so that the area defined by rect is just visible inside the scroll view. If the area is already visible, the method does nothing.

From: https://developer.apple.com/documentation/uikit/uiscrollview/1619439-scrollrecttovisible

Answer 6

Swift 3

let point = CGPoint(x: 0, y: 200) // 200 or any value you like.
scrollView.contentOffset = point

Answer 7

scrollView.setContentOffset(CGPoint(x: y, y: x), animated: true)

Answer 8

[Scrollview setContentOffset:CGPointMake(x, y) animated:YES];

Answer 9

- (void)viewDidLoad
{
    [super viewDidLoad];
    board=[[UIView alloc]initWithFrame:CGRectMake(0, 0, self.view.frame.size.height, 80)];
    board.backgroundColor=[UIColor greenColor];
    [self.view addSubview:board];
    // Do any additional setup after loading the view.
}


-(void)viewDidLayoutSubviews
{


    NSString *str=@"ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    index=1;
    for (int i=0; i<20; i++)
    {
        UILabel *lbl=[[UILabel alloc]initWithFrame:CGRectMake(-50, 15, 50, 50)];
        lbl.tag=i+1;
        lbl.text=[NSString stringWithFormat:@"%c",[str characterAtIndex:arc4random()%str.length]];
        lbl.textColor=[UIColor darkGrayColor];
        lbl.textAlignment=NSTextAlignmentCenter;
        lbl.font=[UIFont systemFontOfSize:40];
        lbl.layer.borderWidth=1;
        lbl.layer.borderColor=[UIColor blackColor].CGColor;
        [board addSubview:lbl];
    }

    [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(CallAnimation) userInfo:nil repeats:YES];

    NSLog(@"%d",[board subviews].count);
}


-(void)CallAnimation
{

    if (index>20) {
        index=1;
    }
    UIView *aView=[board viewWithTag:index];
    [self doAnimation:aView];
    index++;
    NSLog(@"%d",index);
}

-(void)doAnimation:(UIView*)aView
{
    [UIView animateWithDuration:10 delay:0 options:UIViewAnimationOptionCurveLinear  animations:^{
        aView.frame=CGRectMake(self.view.frame.size.height, 15, 50, 50);
    }
                     completion:^(BOOL isDone)
     {
         if (isDone) {
             //do Somthing
                        aView.frame=CGRectMake(-50, 15, 50, 50);
         }
     }];
}

Answer 10

Here is another use case which worked well for me.

1. User tap a button/cell.
2. Scroll to a position just enough to make a target view visible.

Code: Swift 5.3

// Assuming you have a view named "targeView"
scrollView.scroll(to: CGPoint(x:targeView.frame.minX, y:targeView.frame.minY), animated: true)

As you can guess if you want to scroll to make a bottom part of your target view visible then use maxX and minY.

Answer 11

I am showing how to create a simple scroll view with two UIView and add some auto layout constraints so that it will scroll smoothly.

I am supposing that you have an empty view controller in main.storyboard.

1.Add a UIView .

let view = UIView()
    view.backgroundColor = UIColor.green
    self.view.addSubview(view)
    view.translatesAutoresizingMaskIntoConstraints = false
    top = view.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 0)
    left = view.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 0)
    right = view.rightAnchor.constraint(equalTo: self.view.rightAnchor, constant: 0)
    bottom = view.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: 0)
    height = view.heightAnchor.constraint(equalToConstant: self.view.frame.height)
    NSLayoutConstraint.activate([top, right, left, height, bottom])

2.Add a ScrollView .

let scroll = UIScrollView()
    scroll.backgroundColor = UIColor.red
    view.addSubview(scroll)
    scroll.translatesAutoresizingMaskIntoConstraints = false
    top = scroll.topAnchor.constraint(equalTo: view.topAnchor, constant: 10)
    left = scroll.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0)
    right = scroll.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0)
    bottom = scroll.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -10)
    NSLayoutConstraint.activate([top, right, left, bottom])

3.Add first UILabel .

 let l2 = UILabel()
        l2.text = "Label1"
        l2.textColor = UIColor.black
        l2.backgroundColor = UIColor.blue
        scroll.addSubview(l2)
        l2.translatesAutoresizingMaskIntoConstraints = false
        top = l2.topAnchor.constraint(equalTo: scroll.topAnchor, constant: 10)
        left = l2.leadingAnchor.constraint(equalTo: scroll.leadingAnchor, constant: 10)
        height = l2.heightAnchor.constraint(equalToConstant: 100)
        right = l2.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -10)
        NSLayoutConstraint.activate([top, left, right, height])

4.Add Second UILabel .

let l1 = UILabel()
    l1.text = "Label2"
    l1.textColor = UIColor.black
    l1.backgroundColor = UIColor.blue
    scroll.addSubview(l1)
    l1.translatesAutoresizingMaskIntoConstraints = false
    top = l1.topAnchor.constraint(equalTo: scroll.topAnchor, constant: 1000)
    left = l1.leadingAnchor.constraint(equalTo: scroll.leadingAnchor, constant: 10)
    bottom = l1.bottomAnchor.constraint(equalTo: scroll.bottomAnchor, constant: -10)
    height = l1.heightAnchor.constraint(equalToConstant: 100)
    right = l1.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -10)
    NSLayoutConstraint.activate([left, bottom, right, height, top])