1实现原理

 创建一个自定义控件，控件中显示文本，同时设置一个动画，三秒钟后，控件的alpha为0,动画完成后，控件移出掉ViewControl

 

2 创建PopView

2.1 PopView.h 部分

@interface PopView : UIView{    UILabel         *_textLabel;    int             _queueCount;}- (void) setText:(NSString *) text;@end

2.2 PopView.m

#import "PopView.h"#import 
     
      @implementation PopView- (id)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self) {        self.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent: 0.75f];        self.layer.cornerRadius = 5.0f;        _textLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 10)];        _textLabel.numberOfLines = 0;        _textLabel.font = [UIFont systemFontOfSize:17];        _textLabel.textColor = [UIColor whiteColor];        _textLabel.textAlignment = NSTextAlignmentCenter;        _textLabel.backgroundColor = [UIColor clearColor];        _textLabel.textAlignment = NSTextAlignmentCenter;        [self addSubview:_textLabel];        _queueCount = 0;    }    return self;}- (void) setText:(NSString *) text{    _textLabel.frame = CGRectMake(0, 0, 100, 10);    _queueCount ++;    self.alpha = 1.0f;    _textLabel.text = text;    [_textLabel sizeToFit];    CGRect frame = CGRectMake(5, 0, _textLabel.frame.size.width, _textLabel.frame.size.height);    _textLabel.frame = frame;   frame =  CGRectMake(self.frame.origin.x, self.frame.origin.y, _textLabel.frame.size.width+10, _textLabel.frame.size.height+10);    self.frame = frame;    [UIView animateWithDuration:3.0                          delay:0.0                        options:UIViewAnimationOptionCurveEaseIn                     animations:^{                         self.alpha = 0;                     }                     completion:^(BOOL finished){                         if (_queueCount == 1) {                             [self removeFromSuperview];                         }                        _queueCount--;                     }     ];    }@end
     

3 调用方式：

[self.view addSubview:_popView];    [_popView setText:@"合成恢复"];