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当当当当，我胡汉三又回来了。今天介绍实现聊天的聊天框随文本升高，效果图如下
接下来让我们一步一步实现这个功能吧
1.创建一个UITextView的分类 UITextView+AutoRise
@interface UITextView (AutoRise) @property (nonatomic, assign) CGFloat defaultHeight; @property (nonatomic, assign) CGFloat maxHeight; @property (nonatomic, copy) void (^handler)(CGFloat expectHeight); - (void)addAutoRiseHandlerWithdefaultHeight:(CGFloat)defaultHeight maxHeight:(CGFloat)maxHeight handler:(void (^)(CGFloat expectHeight))handler; @end
接下来实现
- (void)addAutoRiseHandlerWithdefaultHeight:maxHeight:handler:方法
- (void)addAutoRiseHandlerWithdefaultHeight:(CGFloat)defaultHeight maxHeight:(CGFloat)maxHeight handler:(void (^)(CGFloat))handler { self.defaultHeight = defaultHeight; self.maxHeight = maxHeight; self.handler = handler; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChange:) name:UITextViewTextDidChangeNotification object:nil]; }
因为是在分类中添加属性，所以需要使用runtime的关联对象(AssociatedObject)来添加。
- (CGFloat)maxHeight { return [objc_getAssociatedObject(self, UITextRiseMaxHeight) floatValue]; } - (CGFloat)defaultHeight { return [objc_getAssociatedObject(self, UITextRiseDefaultHeight) floatValue]; } - (void (^)(CGFloat))handler { return objc_getAssociatedObject(self, UITextRiseHandler); } -(void)setDefaultHeight:(CGFloat)defaultHeight { objc_setAssociatedObject(self, UITextRiseDefaultHeight, @(defaultHeight), OBJC_ASSOCIATION_RETAIN); } - (void)setMaxHeight:(CGFloat)maxHeight { objc_setAssociatedObject(self, UITextRiseMaxHeight, @(maxHeight), OBJC_ASSOCIATION_RETAIN); } - (void)setHandler:(void (^)(CGFloat))handler { objc_setAssociatedObject(self, UITextRiseHandler, handler, OBJC_ASSOCIATION_COPY_NONATOMIC); }
现在我们来实现textChange:方法
- (void)textChange:(NSNotification *)noti { UITextView *inputTextView = noti.object; if (inputTextView != self) { return; } CGFloat expectHeight = 0.f; CGSize contentSize = inputTextView.contentSize; if(contentSize.height <= self.defaultHeight){ expectHeight = self.defaultHeight; }else{ expectHeight = contentSize.height; expectHeight = expectHeight > self.maxHeight ? self.maxHeight : expectHeight; if (expectHeight < self.maxHeight) { [inputTextView setContentOffset:CGPointMake(0, 0) animated:NO]; } } if (self.handler) { self.handler(expectHeight); } }
2.在StoryBoard中添加一个TextView，并设置好约束
将高度约束关联到控制器
3.在ViewDidLoad:中根据自己的需求设置自动升高
- (void)viewDidLoad { [super viewDidLoad]; [_textView addAutoRiseHandlerWithdefaultHeight:_textViewHeightConstraint.constant maxHeight:100 handler:^(CGFloat expectHeight) { _textViewHeightConstraint.constant = expectHeight; [_textView layoutIfNeeded]; }]; }
至此自动升高就完成了。
1.在StoryBoard中创建一个控制器(省略)
2.在控制器中添加一个view作为聊天的背景框 bottomBackgroundView
为背景设置一个背景色，并且设置好约束，见图
3.在bottomBackgroundView中添加一个textView
为textView添加好约束，见图
4.将添加的控件与控制器关联
5.在控制器中设置处理代码
- (void)viewDidLoad { [super viewDidLoad]; __weak typeof(self)weakSelf = self; CGFloat defaultHeight = _bottomBackgroundViewHeightConstraint.constant - 8 * 2;//默认高度 [_textView addAutoRiseHandlerWithdefaultHeight:defaultHeight maxHeight:100.f handler:^(CGFloat expectHeight) { __strong typeof(weakSelf) strongSelf = weakSelf; strongSelf.bottomBackgroundViewHeightConstraint.constant = expectHeight + 8 * 2; [strongSelf.bottomBackgroundView layoutIfNeeded]; }]; }
效果如下：
你可以从这里下载[demo]
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原文地址：http://www.cnblogs.com/pretty-guy/p/5783545.html
