这一次学习一下 updateConstraints 和 remakeConstraints
先看一下 updateConstraints ，我们做一个能够放大的按钮来实验一下
- (void)updateConstraints{
self.growingButton = [UIButton buttonWithType:UIButtonTypeSystem];
[self.growingButton setTitle:@"点我放大" forState:UIControlStateNormal];
self.growingButton.layer.borderColor = UIColor.greenColor.CGColor;
self.growingButton.layer.borderWidth = 3;
[self.growingButton addTarget:self action:@selector(onGrowButtonTaped:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:self.growingButton];
//记录增加的量
self.scacle = 1.0;
[self.growingButton mas_updateConstraints:^(MASConstraintMaker *make) {
//让按钮始终居中
make.center.mas_equalTo(self.view);
// 初始宽、高为100，优先级最低，就可以保证宽高不能超过屏幕。
make.width.height.mas_equalTo(100 * self.scacle).priorityLow();
// 最大放大到整个view
make.width.height.lessThanOrEqualTo(self.view);
}];
}
- (void)updateViewConstraints {
[self.growingButton mas_updateConstraints:^(MASConstraintMaker *make) {
make.center.mas_equalTo(self.view);
// 初始宽、高为100，优先级最低
make.width.height.mas_equalTo(100 * self.scacle).priorityLow();
// 最大放大到整个view
make.width.height.lessThanOrEqualTo(self.view);
}];
[super updateViewConstraints];
}
- (void)onGrowButtonTaped:(UIButton *)sender {
self.scacle += 0.5;
// 告诉self.view约束需要更新，这个比较重要
[self.view setNeedsUpdateConstraints];
// 调用此方法告诉self.view检测是否需要更新约束，若需要则更新，下面添加动画效果才起作用
[self.view updateConstraintsIfNeeded];
[UIView animateWithDuration:0.3 animations:^{
//我们要使约束立即生效，就必须调用layoutIfNeeded此方法
[self.view layoutIfNeeded];
}];
}
效果就是每次你点击按钮的时候都会变大
再看一下 remakeConstraints
- (void)remarkConstraints{
self.remarkButton = [UIButton buttonWithType:UIButtonTypeSystem];
[self.remarkButton setTitle:@"点我展开" forState:UIControlStateNormal];
self.remarkButton.layer.borderColor = UIColor.greenColor.CGColor;
self.remarkButton.layer.borderWidth = 3;
self.remarkButton.backgroundColor = [UIColor lightGrayColor];
[self.remarkButton addTarget:self action:@selector(onGrowButtonTaped:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:self.remarkButton];
self.isExpanded = NO;
[self.remarkButton mas_remakeConstraints:^(MASConstraintMaker *make) {
make.top.mas_equalTo(0);
make.left.right.mas_equalTo(0);
make.bottom.mas_equalTo(-350);
}];
}
- (void)updateViewConstraints {
// 这里使用update也是一样的。
// remake会将之前的全部移除，然后重新添加
WS(weakSelf);
[self.remarkButton mas_remakeConstraints:^(MASConstraintMaker *make) {
make.top.mas_equalTo(0);
make.left.right.mas_equalTo(0);
if (weakSelf.isExpanded) {
make.bottom.mas_equalTo(0);
} else {
make.bottom.mas_equalTo(-350);
}
}];
[super updateViewConstraints];
}
- (void)onGrowButtonTaped:(UIButton *)sender {
self.isExpanded = !self.isExpanded;
if (!self.isExpanded) {
[self.remarkButton setTitle:@"点我展开" forState:UIControlStateNormal];
} else {
[self.remarkButton setTitle:@"点我收起" forState:UIControlStateNormal];
}
// 告诉self.view约束需要更新，这个比较重要
[self.view setNeedsUpdateConstraints];
// 调用此方法告诉self.view检测是否需要更新约束，若需要则更新，下面添加动画效果才起作用
[self.view updateConstraintsIfNeeded];
[UIView animateWithDuration:0.3 animations:^{
//我们要使约束立即生效，就必须调用layoutIfNeeded此方法
[self.view layoutIfNeeded];
}];
}
来看一下效果
这里就是说明一下我们之前提到的
mas_makeConstraints 只负责新增约束 Autolayout不能同时存在两条针对于同一对象的约束 否则会报错
mas_updateConstraints 针对上面的情况 会更新在block中出现的约束 不会导致出现两个相同约束的情况
mas_remakeConstraints 则会清除之前的所有约束 仅保留最新的约束