autolayout1.gif

//遍历父控件的约束,通过 firstItem 和firstAttribute 来确定某一约束,或者通过 identifier(xib必须先设置好)确定,
  for (NSLayoutConstraint * con in _titleLabel.superview.constraints) {
        
        if (con.firstItem == _titleLabel && con.firstAttribute == NSLayoutAttributeCenterX) {
            con.constant = isMenuOpen ? -100:0;
            continue;
        }
        
        if ([con.identifier isEqualToString:@"TitleCenterY"]) {
            con.active = false;
            [_titleLabel.superview removeConstraint:con];
            //代码添加约束
            NSLayoutConstraint * newCon = [NSLayoutConstraint constraintWithItem:_titleLabel attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:_titleLabel.superview attribute:NSLayoutAttributeCenterY multiplier:isMenuOpen? 0.67 :1.0 constant:0.5];
            newCon.identifier = @"TitleCenterY";
            newCon.active = YES;
            continue;
        }
    }

3.如何让约束产生动画效果? [self.view layoutIfNeeded];

// 旋转 + 按钮
    [UIView animateWithDuration:1 delay:0 usingSpringWithDamping:0.3 initialSpringVelocity:10 options:UIViewAnimationOptionCurveEaseInOut animations:^{
        [self.view layoutIfNeeded];
        CGFloat angle = isMenuOpen ? M_PI_4 : 0;
        _menuBtn.transform = CGAffineTransformMakeRotation(angle);
    } completion:^(BOOL finished) {
        
    }];

4.如何给通过代码创建的控件添加约束?

//6.0
UIImageView * imageView = [[UIImageView alloc] initWithImage:image];
    [self.view addSubview:imageView];
imageView.translatesAutoresizingMaskIntoConstraints = NO;
NSLayoutConstraint * newCon = [NSLayoutConstraint constraintWithItem:_imageView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:_self.view attribute:NSLayoutAttributeCenterY multiplier:isMenuOpen? 0.67 :1.0 constant:0.5];
            newCon.identifier = @"TitleCenterY";
            newCon.active = YES;

//9.0 新出的方法
UIImageView * imageView = [[UIImageView alloc] initWithImage:image];
    [self.view addSubview:imageView];
  imageView.translatesAutoresizingMaskIntoConstraints = NO;
    NSLayoutConstraint *conX = [imageView.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor]; // centerX
     NSLayoutConstraint * conBottom = [imageView.bottomAnchor constraintEqualToAnchor:self.view.bottomAnchor constant:imageView.frame.size.height]; // bottom 往下移动imageViewHeight距离
    NSLayoutConstraint * conWidth = [imageView.widthAnchor constraintEqualToAnchor:self.view.widthAnchor multiplier:0.33 constant:-50]; // 确定宽度
    CGFloat scale = image.size.height / image.size.width;
    NSLayoutConstraint * conHeight = [imageView.heightAnchor constraintEqualToAnchor:imageView.widthAnchor multiplier:scale]; // 宽高相等
    [NSLayoutConstraint activateConstraints:@[conX,conBottom,conHeight,conWidth]];
    [self.view layoutIfNeeded];

871DB054-1AF5-4338-ADB1-983B029BB4FF.png

5.如何给刚创建出来的控件,添加动画效果?
重写 didMoveToSuperview,

-(void)didMoveToSuperview{
    [super didMoveToSuperview];
    if (!self.superview) {
        return;
    }
    
    [UIView animateWithDuration:1 delay:0.03 usingSpringWithDamping:0.3 initialSpringVelocity:10 options:UIViewAnimationOptionCurveEaseIn animations:^{
        self.alpha = 1.0;
        CGPoint center = self.center;
        center.x -= self.superview.bounds.size.width;
        self.center = center;
    } completion:^(BOOL finished) {
        
    }];
}