目录
- UIDatePicker
- 如何暂停和恢复CALayer的动画
- requireGestureRecognizerToFail:
- URLEncode
- 用AVSpeechSynthesizer实现文本转语音
1.UIDatePicker
UIDatePicker在设置datePickerMode为UIDatePickerModeCountDownTimer时，当第一次valueChange的时候target的action不会调用，之后的valueChange都响应正常，解决代码如下:
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| self.datePicker = [UIDatePicker new];
self.datePicker.datePickerMode = UIDatePickerModeCountDownTimer;
self.datePicker.backgroundColor = [UIColor whiteColor];
[self.datePicker addTarget:self action:@selector(onDatePickerValueChanged:) forControlEvents:UIControlEventValueChanged];
//增加这三行代码
dispatch_async(dispatch_get_main_queue(), ^{
self.datePicker.countDownDuration = (NSTimeInterval) 1;
});
[self addSubview:self.datePicker];
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参考链接:http://stackoverflow.com/questions/20181980/uidatepicker-bug-uicontroleventvaluechanged-after-hitting-minimum-internal
2.如何暂停和恢复CALayer的动画:
示例代码如下：
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| -(void)pauseLayer:(CALayer*)layer
{
CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
layer.speed = 0.0;
layer.timeOffset = pausedTime;
}
-(void)resumeLayer:(CALayer*)layer
{
CFTimeInterval pausedTime = [layer timeOffset];
layer.speed = 1.0;
layer.timeOffset = 0.0;
layer.beginTime = 0.0;
CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
layer.beginTime = timeSincePause;
}
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参考链接:https://developer.apple.com/library/ios/qa/qa1673/_index.html
3.requireGestureRecognizerToFail:
UIView添加手势很常用，当添加两个或两个以上的手势时，需要使用requireGestureRecognizerToFail:方法来创建手势之间的依赖关系，常见的用法是当同时添加单击和双击手势时single-tap的手势会要求double-tap手势fail掉，示例如下:
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| //添加单击手势
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onSingleTapGestureHandled:)];
singleTap.numberOfTapsRequired = 1;
singleTap.numberOfTouchesRequired = 1;
[self.view addGestureRecognizer:singleTap];
//添加双击手势
UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onDoubleTapGestureHandled:)];
doubleTap.numberOfTapsRequired = 2;
doubleTap.numberOfTouchesRequired = 1;
//注意是单击手势requireGestureRecognizerToFail:双击
[singleTap requireGestureRecognizerToFail:doubleTap];
[self.view addGestureRecognizer:doubleTap];
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当单击和长按手势一起添加时，不需要调用requireGestureRecognizerToFail:方法，因为两者之间不会影响对方的state判断，如果调用了
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| [longPressGesture requireGestureRecognizerToFail:singleTapGesture];
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会导致长按手势响应时间变长，由默认的0.5秒变成1.5秒左右,而调用
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| [singleTapGesture requireGestureRecognizerToFail:longPressGesture];
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则不会出现这种情况。因为- (void)requireGestureRecognizerToFail:(UIGestureRecognizer *)otherGestureRecognizer会导致otherGestureRecognizer延迟进入Possible状态，进而使得longPressGesture转换成Recognized的时间变长从而严重影响用户体验。哎，官方文档还是得多看啊！
4.URLEncode
跟web服务器打交道的时候，经常需要对URL进行Encode，不然可能出现各种error，下面以图片加载为例:
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| NSString *urlString = @"http://s.checkin.tx2010.com/20160302175840/在路上.jpg";
NSURL *url = [NSURL URLWithString:urlString];
NSLog(@"url:%@",url);
//打印结果url:(null)
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因为没有对链接encode编码，导致用URLWithString:转成NSURL时对象为空，以至于用SDWebImage加载时图片显示不出来,修改逻辑如下：
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| NSString *urlString = @"http://s.checkin.tx2010.com/20160302175840/在路上.jpg";
//注:iOS9已废弃stringByAddingPercentEscapesUsingEncoding:方法
//urlString = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
//此处使用URLQueryAllowedCharacterSet来满足需求
urlString = [urlString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];
NSURL *url = [NSURL URLWithString:urlString];
NSLog(@"url:%@",url);
//打印结果url:http://s.checkin.tx2010.com/20160302175840/%E5%9C%A8%E8%B7%AF%E4%B8%8A.jpg
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转换后的url正常，使用SDWebImage加载时图片也显示正常了，问题解决。
5.用AVSpeechSynthesizer实现文本转语音
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| NSString *name = @"cocoa_chen你好";
AVSpeechSynthesizer *speechSynthesizer = [AVSpeechSynthesizer new];
AVSpeechUtterance *utterance = [[AVSpeechUtterance alloc]initWithString:name];
//设置为中文语音
utterance.voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"zh-CN"];
utterance.volume = 1.0f;
//说话速率
utterance.rate = 0.5f;
[speechSynthesizer speakUtterance:utterance];
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