更改NSLayoutConstraint常量在layoutSubviews中不起作用 [英] Change NSLayoutConstraint constant not working in layoutSubviews

问题描述

当视图动画化为横向模式时，我正在尝试更改UIButton的宽度.但是之所以调用该方法，是因为我在此处设置了一个断点，但是按钮的宽度没有改变.我将IBOutlet约束添加到名为widthglobalButtonWidthConstraint的按钮宽度上.

I am trying to change a UIButton's width when the view animates to landscape mode. But the method is called because I set a break point there, but the button's width doesn't change. I add a IBOutlet constraint to button's width named: globalButtonWidthConstraint.

我当前的代码:

- (void)layoutSubviews {
    [super layoutSubviews];

    CGSize screenSize = [[UIScreen mainScreen] bounds].size;
    CGFloat screenH = screenSize.height;
    CGFloat screenW = screenSize.width;
    BOOL isLandscape =  !(self.frame.size.width == (screenW*(screenW<screenH))+(screenH*(screenW>screenH)));

    if (isLandscape) {
        self.globalButtonWidthConstraint.constant = 100;
        [self layoutIfNeeded];
    } else {
        self.globalButtonWidthConstraint.constant = 47;
        [self layoutIfNeeded];
    }
}

推荐答案

尝试在"viewDidLayoutSubviews"中更新约束常量.

Try updating constraint constant in "viewDidLayoutSubviews".

 -(void)viewDidLayoutSubviews
{

   [super viewDidLayoutSubviews];

  // Update constraint constant

   [self.view layoutSubviews];

}

对我有用.

编辑:确保没有其他与该宽度约束冲突的约束.

Make sure that there is no other constraints that conflicting this width constraint.

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