iOS 8 UIView 没有得到更新的问题

Question

我有一个带有 UITextField 的 UIView 位于屏幕底部，我想在出现键盘时将其向上移动。我添加了 keyboardFrameDidChange 观察器，以便在键盘出现/消失时得到通知。这是方法:

-(void)keyboardFrameDidChange:(NSNotification*)notification{

NSDictionary* info = [notification userInfo];

CGRect kKeyBoardFrame = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

[bottomView layoutIfNeeded];

[UIView animateWithDuration:[notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue] delay:0 options:[[[notification userInfo] objectForKey:UIKeyboardAnimationCurveUserInfoKey] integerValue] animations:^{

    [bottomView setFrame:CGRectMake(0, kKeyBoardFrame.origin.y - bottomView.frame.size.height, 320, bottomView.frame.size.height)];

} completion:^(BOOL finished) {

    [bottomView layoutIfNeeded];

    NSLog(@"frame ** %f",self.bottomView.frame.origin.y);
}];
}

此处 bottomView 的框架 发生了变化，但 UI 中没有任何反应。 bottomView 只保留在底部。可能是什么原因？

Answer 1

这听起来像是一个自动布局问题。如果自动布局打开，那么您应该通过调整其约束来更改 View 的位置，而不是设置框架。为文本字段和 super View 底部(在我的示例中为bottomCon)之间的约束创建一个IBOutlet，并对其进行调整。

-(void)keyboardFrameDidChange:(NSNotification*)notification{

    NSDictionary* info = [notification userInfo];

    CGRect kKeyBoardFrame = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

    [_bottomView layoutIfNeeded];

    [UIView animateWithDuration:[notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue] delay:0 options:[[[notification userInfo] objectForKey:UIKeyboardAnimationCurveUserInfoKey] integerValue] animations:^{

        self.bottomCon.constant = kKeyBoardFrame.origin.y;
        [_bottomView layoutIfNeeded];
    } completion:^(BOOL finished) {
        NSLog(@"frame ** %f",self.bottomView.frame.origin.y);
    }];
}