• (void)viewDidLoad {
  //增加监听，当键盘出现或改变时收出消息
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];

//增加监听，当键退出时收出消息
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}
//当键盘出现或改变时调用

• (void)keyboardWillShow:(NSNotification *)aNotification
  {
  //获取键盘的高度
  NSDictionary *userInfo = [aNotification userInfo];
  NSValue *aValue = [userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];
  CGRect keyboardRect = [aValue CGRectValue];
  int height = keyboardRect.size.height;
  NSLog(@"==%d",height);
  }

//当键退出时调用

• (void)keyboardWillHide:(NSNotification *)aNotification{}

//获取键盘的高度
NSDictionary *userInfo = [aNotification userInfo];
NSValue *aValue = [userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];
CGRect keyboardRect = [aValue CGRectValue];
int height = keyboardRect.size.height;
NSLog(@"===%d",height);
// 获取键盘弹出动画时间
NSValue *animationDurationValue = [userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey];
NSTimeInterval animationDuration;
[animationDurationValue getValue:&animationDuration];

 NSLog(@"键盘弹起的时间===%@",animationDurationValue);

UIGraphics

• (void)drawViewsWithRect:(CGRect)rect
  {
  self.backgroundColor = [UIColor whiteColor];
  UIImageView *ima = [[UIImageView alloc] initWithFrame:rect];
  UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
  UIImage *myIma = _iconImage;
  [myIma drawInRect:CGRectMake(20, 5, 34, 34)];
  NSString *nameStr = _nameString;
  [nameStr drawInRect:CGRectMake(60, 5, 200, 34) withAttributes:@{NSFontAttributeName: [UIFont fontWithName: @"Zapfino" size: 15]}];
  UIImage* im = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  ima.image = im;
  [self addSubview:ima];
  NSLog(@"%s",FUNCTION)
  }

屏幕刷新

_disPlayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateWave:)];
_disPlayLink.frameInterval = 3;//刷新频率 1-60 2-30 3-20
[_disPlayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
/**
保持和屏幕的刷新速度相同，iphone的刷新速度是60Hz,即每秒60次的刷新
*/
-(void)updateWave:(CADisplayLink *)link
{
}

• (void)viewDidLoad {
  NSString *str = @"000068976897230253444b2076657273696f00106e3a322e302e302835613837356261290020776966693a312e30";
  NSString *charStr = [self convertHexStrToString:str];
  NSLog(@"%@",charStr);
  }

//16进制转字符串

• (NSString *)convertHexStrToString:(NSString *)str {
  if (!str || [str length] == 0) {
  return nil;
  }

NSMutableData *hexData = [[NSMutableData alloc] initWithCapacity:8];
NSRange range;
if ([str length] % 2 == 0) {
range = NSMakeRange(0, 2);
} else {
range = NSMakeRange(0, 1);
}
for (NSInteger i = range.location; i < [str length]; i += 2) {
unsigned int anInt;
NSString *hexCharStr = [str substringWithRange:range];
NSNumber *nb = [self numberHexString:hexCharStr];
NSScanner *scanner = [[NSScanner alloc] initWithString:hexCharStr];
[scanner scanHexInt:&anInt];
NSData *entity = [[NSData alloc] initWithBytes:&anInt length:1];
if ([nb integerValue] > 32 && [nb integerValue] < 127)
{
[hexData appendData:entity];
}
range.location += range.length;
range.length = 2;
}
NSString *string = [[NSString alloc]initWithData:hexData encoding:NSASCIIStringEncoding];
return string;
}

//16进制转10进制

• (NSNumber *) numberHexString:(NSString *)aHexString
  {
  // 为空,直接返回.
  if (nil == aHexString)
  {
  return nil;
  }
  NSScanner * scanner = [NSScanner scannerWithString:aHexString];
  unsigned long long longlongValue;
  [scanner scanHexLongLong:&longlongValue];
  //将整数转换为NSNumber,存储到数组中,并返回.
  NSNumber * hexNumber = [NSNumber numberWithLongLong:longlongValue];
  return hexNumber;
  }

//语音合成

import <AVFoundation/AVFoundation.h>

AVSpeechSynthesizer *synth2 = [[AVSpeechSynthesizer alloc] init];
AVSpeechUtterance *utterance1 = [AVSpeechUtterance speechUtteranceWithString:@" 你瞅啥，瞅你咋滴"];//播放语
AVSpeechSynthesisVoice *voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"zh-CN"];//汉语
utterance1.voice = voice;
utterance1.rate = 0.5;//语速
[synth2 speakUtterance:utterance1];//播放

//一篇介绍音频的帖子

http://www.cnblogs.com/SunnyOMGi/p/5620762.html

//判断文件是否已经在沙盒中已经存在？

-(BOOL) isFileExist:(NSString *)fileName
{
//NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);//判断Caches
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);//判断Document
NSString *path = [paths objectAtIndex:0];
NSString *filePath = [path stringByAppendingPathComponent:fileName];
NSFileManager *fileManager = [NSFileManager defaultManager];
BOOL result = [fileManager fileExistsAtPath:filePath];
NSLog(@"这个文件已经存在：%@",result?@"是的":@"不存在");
return result;
}

- (void)setupTextView
{
    UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0, 100, [UIScreen mainScreen].bounds.size.width, 100];

    [textView setBackgroundColor:[UIColor greenColor]];
    [self.view addSubview:textView];
    
    // _placeholderLabel
    UILabel *placeHolderLabel = [[UILabel alloc] init];
    placeHolderLabel.text = @"请输入内容";
    placeHolderLabel.numberOfLines = 0;
    placeHolderLabel.textColor = [UIColor lightGrayColor];
    [placeHolderLabel sizeToFit];
    [textView addSubview:placeHolderLabel];

    // same font
    textView.font = [UIFont systemFontOfSize:13.f];
    placeHolderLabel.font = [UIFont systemFontOfSize:13.f];

    [textView setValue:placeHolderLabel forKey:@"_placeholderLabel"];
}