如何使用約束添加兩個視圖

Question

我試圖用相同的X，Y添加2個視圖。他們使用addConstraints:[NSLayoutConstraint constraintsWithVisualFormat...]從邊緣有空間addConstraints:[NSLayoutConstraint constraintsWithVisualFormat...]

我試過字符串"H:|20-[A][B]-20-[C]-20-[D]-20|" 和V:|20-[A][B]-20-[C]-20-[D]-20| ，和centreX == CenterX和centerY==centerY ，但他們保持沖突，認為A和B應該是彼此相鄰的。

A被隱藏，點擊某個按鈕，B被隱藏，並顯示A.

Answer 1

要添加具有相同中心X的視圖，Y您需要先使用constatins放置一個視圖bView（底視圖）

NSArray * bVerticalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"|-20-[bView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(bView)];
    NSArray * bHorizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[bView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(bView)];

這將bView置於superview中，並將20作為邊緣偏移。

現在將tView（頂視圖）放在與bView相同的中心。 這里的自我是bView和tView的超級視圖

[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[bView]-(<=1)-[tView]" options:NSLayoutFormatAlignAllCenterX metrics:nil views:NSDictionaryOfVariableBindings(bView,tView)]];
    [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[bView]-(<=1)-[tView]" options:NSLayoutFormatAlignAllCenterY metrics:nil views:NSDictionaryOfVariableBindings(bView,tView)]];

然后將tView的邊緣固定為所需的偏移量40

NSArray * tVerticalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"|-40-[tView]-40-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(tView)];
    NSArray * tHorizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-40-[tView]-40-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(tView)];

編輯：

這是怎么做的。

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    bView = [UIView new];
    bView.backgroundColor = [UIColor redColor];
    bView.translatesAutoresizingMaskIntoConstraints = NO;

    tView = [UIView new];
    tView.backgroundColor = [UIColor blackColor];
    tView.translatesAutoresizingMaskIntoConstraints = NO;

    // Firdt bView is added then tView hence tView is exaclty above the bView.
    [self.view addSubview:bView];
    [self.view addSubview:tView];


    // Edges Constrints for bView
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-20-[bView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(bView)]];
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[bView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(bView)]];

    // Edges Constints for tView
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-20-[tView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(tView)]];
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[tView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(tView)]];

    // Centring for bView and tView
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[bView]-(<=1)-[tView]" options:NSLayoutFormatAlignAllCenterX metrics:nil views:NSDictionaryOfVariableBindings(bView,tView)]];
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[bView]-(<=1)-[tView]" options:NSLayoutFormatAlignAllCenterY metrics:nil views:NSDictionaryOfVariableBindings(bView,tView)]];

}

-(IBAction)toggleViews:(id)sender {
    NSArray * subViews = self.view.subviews;
    [self.view exchangeSubviewAtIndex:[subViews indexOfObject:tView] withSubviewAtIndex:[subViews indexOfObject:bView]];
}