ios - 单击时将 UiScrollView 元素置于中心

Question

我有的是 UIScrollView，里面有不同大小的按钮。

- (void)viewDidLoad {
    [super viewDidLoad];

    myScrollView.frame = CGRectMake(0, 100, 375, 50.0);

    int totalButtonsToAdd = 20;

    startX = 0;
    int buttonWidth =  60;
    for (int i=0;i<totalButtonsToAdd;i++) {
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        [button addTarget:self
                   action:@selector(aMethod:)
         forControlEvents:UIControlEventTouchUpInside];
        [button setTitle:[NSString stringWithFormat:@"Btn-%d", i] forState:UIControlStateNormal];
        [button setTitleColor:[UIColor greenColor] forState:UIControlStateNormal];
        button.accessibilityValue = [NSString stringWithFormat:@"%d", i+1];
        button.frame = CGRectMake(startX, 0, buttonWidth, 50.0);
        [[button layer] setBorderWidth:2.0f];
        [[button layer] setBorderColor:[UIColor greenColor].CGColor];
        button.layer.cornerRadius = 5;
        startX = startX + buttonWidth + 5;
        buttonWidth = buttonWidth + 5;
        [myScrollView addSubview:button];
    }

    NSLog(@"startX===%d", startX);

    myScrollView.contentSize = CGSizeMake(startX, 50.0);
}

-(IBAction)aMethod:(id)sender {
    UIButton *mButton = (UIButton *)sender;
    NSLog(@"clicked button index is %@", mButton.accessibilityValue);
}

我想做的是当我点击任何按钮时，我想把那个按钮放在中间。为此，我相信我需要将 ScrollView 滚动到特定位置。

为此我所做的如下。

- (void)viewDidLoad {
    [super viewDidLoad];

    myScrollView.frame = CGRectMake(0, 100, 375, 50.0);

    int totalButtonsToAdd = 20;

    startX = 0;
    int buttonWidth =  60;
    for (int i=0;i<totalButtonsToAdd;i++) {
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        [button addTarget:self
                   action:@selector(aMethod:)
         forControlEvents:UIControlEventTouchUpInside];
        [button setTitle:[NSString stringWithFormat:@"Btn-%d", i] forState:UIControlStateNormal];
        [button setTitleColor:[UIColor greenColor] forState:UIControlStateNormal];
        button.accessibilityValue = [NSString stringWithFormat:@"%d", i+1];
        button.frame = CGRectMake(startX, 0, buttonWidth, 50.0);
        [[button layer] setBorderWidth:2.0f];
        [[button layer] setBorderColor:[UIColor greenColor].CGColor];
        button.layer.cornerRadius = 5;
        startX = startX + buttonWidth + 5;
        NSLog(@"startX===%d==%d", i, startX);
        buttonWidth = buttonWidth + 5;
        [myScrollView addSubview:button];
    }

    NSLog(@"startX final===%d", startX);

    myScrollView.contentSize = CGSizeMake(startX, 50.0);
}

-(IBAction)aMethod:(id)sender {
    UIButton *mButton = (UIButton *)sender;
    NSLog(@"clicked button index is %@", mButton.accessibilityValue);
    focusPosition = 0;
    int totalButtonsToAdd = 20;
    int buttonWidth = 60;
    startX = 0;
    for (int i=0;i<totalButtonsToAdd;i++) {
        startX = startX + buttonWidth + 5;
        buttonWidth = buttonWidth + 5;

        if (i==[mButton.accessibilityValue intValue]) {
            focusPosition = startX;
        }
    }

    NSLog(@"focusPosition===%d", focusPosition);

    CGRect frame = CGRectMake(focusPosition, 0, buttonWidth, 50); //wherever you want to scroll
    [myScrollView scrollRectToVisible:frame animated:NO];


}

然而，这并没有给我我想要的东西。 scrollview 是否有任何属性可以将该按钮置于中心？

Project with above code

注意:此示例仅适用于 iPhone 6。因此，请仅在 iPhone 6 模拟器上运行项目

Answer 1

UICollectionView 可能是比 UIScrollView 更好的选择，因为它添加了一个方法来实现您想要的 (scrollToItemAtIndexPath:atScrollPosition:animated: )。

如果您坚持使用 UIScrollView，则需要改用 setContentOffset:animated:，并计算所需的偏移量，例如:

-(IBAction)aMethod:(UIButton *)button {
    CGPoint contentOffset = CGPointMake(CGRectGetMidX(button.frame) - (CGRectGetWidth(self.scrollView.frame) / 2.0),0.0);

    [myScrollView setContentOffset:contentOffset animated:YES];
}