以textField为例，点击textField 弹出键盘时改变所有的frame。
// 添加键盘将要显示的通知.
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
// 添加将要隐藏的通知.
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHiden:) name:UIKeyboardWillHideNotification object:nil];
#pragma mark ** 键盘将要显示
- (void)keyboardWillShow:(NSNotification *)noti {
// 监听方法会执行多次, 通过BOOL值筛选掉重复的执行.
if (!_isBegin) {
// 修改约束的优先级为 749.
[self textFieldConstraint:self.layoutConstraintForTextField priority:749 fromView:self.view];
[self textFieldConstraint:self.layoutConstraintForButton priority:749 fromView:self.view];
_isBegin ^= 1;
}
}
#pragma mark ** 键盘将要隐藏
- (void)keyboardWillHiden:(NSNotification *)noti {
// 如果isBegin为Yes.
// 说明键盘已经弹出.
if (_isBegin) {
// 修改约束的优先级 900.
[self textFieldConstraint:self.layoutConstraintForTextField priority:900 fromView:self.view];
[self textFieldConstraint:self.layoutConstraintForButton priority:900 fromView:self.view];
_isBegin ^= 1;
}
}
#pragma mark ** 修改优先级方法
- (void)textFieldConstraint:(NSLayoutConstraint *)constraint priority:(float)priority fromView:(UIView *)view {
constraint.priority = priority;
[UIView animateWithDuration:1.5f animations:^{
// 重新布局.
[view layoutIfNeeded];
}];
}
