iOS开发——使用Autolayout弹出键盘

参考：

http://segmentfault.com/q/1010000002420050

http://blog.csdn.net/qq448631961/article/details/40345653

 

思路：

在整个View下面塞进一个高度为0的视图(使用低优先级约束)，当键盘改变时改变该View的高度即可。

 

constraint 有一个唯一可以修改的属性 constant，我承认它的名字确实很具有迷惑性。。。
以题主提到的高度问题为例，可以保存这个高度 constraint 的引用，在键盘出现和收起时

- (void)keyboardDidShowNotification
{
    self.viewHeightConstraint.constant = 100.f;
    [self.myView layoutIfNeed];
}

- (void)keyboardDidHideNotification
{
    self.viewHeightConstraint.constant = 300.f;
    [self.myView layoutIfNeed];
}

 

 

我的代码：

注册通知：

 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillChangeFrameNotification object:nil];

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

 

 

约束

@property (nonatomic,strong) NSLayoutConstraint* keyboardConstraint;

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

 

初始为0

self.keyboardConstraint = [NSLayoutConstraint constraintWithItem:self.keyboardView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0];

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

 

 

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


[code]CGRect kbFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

self.keyboardConstraint.constant = kbFrame.size.height;

[self.view addConstraint:self.keyboardConstraint];

//[self.inputView needsUpdateConstraints];

[self.view setNeedsLayout];

[self.view layoutIfNeeded];

if (self.messages.count > 0){

NSIndexPath *idxP = [NSIndexPath indexPathForRow:(self.messages.count - 1) inSection:0];

[self.tableView scrollToRowAtIndexPath:idxP atScrollPosition:UITableViewScrollPositionBottom animated:YES];}

}

- (void)keyboardWillHidden{

[self.view endEditing:YES];

[UIView animateWithDuration:0.25 animations:^{

//self.keyboardConstraint.constant = 0;

self.keyboardConstraint.constant = 0;

//[self.view removeConstraint:self.keyboardConstraint];

[self.view setNeedsLayout];

[self.view layoutIfNeeded];

}];

}

[/code]

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }