NSData 与 NSString，Byte数组，UIImage 的相互转换

本文详细介绍了在iOS开发中，如何在`NSData`与`NSString`之间进行转换，并展示了实际的应用场景，如图像数据的加载与保存，以及16进制数与字节数组之间的相互转换。

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1. NSData 与 NSString  
  
NSData－> NSString  
  
NSString *aString = [[NSString alloc] initWithData:adataencoding:NSUTF8StringEncoding];  
  
   
  
NSString－>NSData  
  
NSString *aString = @"1234abcd";  
  
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];  
  
   
  
2.NSData 与 Byte  
  
NSData－> Byte数组  
  
NSString *testString = @"1234567890";  
  
NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];  
  
Byte *testByte = (Byte *)[testData bytes];  
  
for(int i=0;i<[testData length];i++)  
  
printf("testByte = %d\n",testByte[i]);  
  
   
  
Byte数组－> NSData  
  
Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};  
  
NSData *adata = [[NSData alloc] initWithBytes:byte length:24];  
  
   
  
Byte数组－>16进制数  
  
Byte *bytes = (Byte *)[aData bytes];  
  
NSString *hexStr=@"";  
  
for(int i=0;i<[encryData length];i++)  
  
{  
  
NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数  
  
if([newHexStr length]==1)  
  
hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];  
  
else   
  
hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];  
  
}  
  
NSLog(@"bytes 的16进制数为:%@",hexStr);  
  
   
  
16进制数－>Byte数组  
  
///// 将16进制数据转化成Byte 数组  
  
NSString *hexString = @"3e435fab9c34891f"; //16进制字符串  
  
int j=0;  
  
Byte bytes[128];  ///3ds key的Byte 数组， 128位  
  
for(int i=0;i<[hexString length];i++)  
  
{  
  
int int_ch;  /// 两位16进制数转化后的10进制数  
  
   
  
unichar hex_char1 = [hexString characterAtIndex:i]; ////两位16进制数中的第一位(高位*16)  
  
int int_ch1;  
  
if(hex_char1 >= '0' && hex_char1 <='9')  
  
int_ch1 = (hex_char1-48)*16;   //// 0 的Ascll - 48  
  
else if(hex_char1 >= 'A' && hex_char1 <='F')  
  
int_ch1 = (hex_char1-55)*16; //// A 的Ascll - 65  
  
else   
  
int_ch1 = (hex_char1-87)*16; //// a 的Ascll - 97  
  
i++;  
  
   
  
unichar hex_char2 = [hexString characterAtIndex:i]; ///两位16进制数中的第二位(低位)  
  
int int_ch2;  
  
if(hex_char2 >= '0' && hex_char2 <='9')  
  
int_ch2 = (hex_char2-48); //// 0 的Ascll - 48  
  
else if(hex_char1 >= 'A' && hex_char1 <='F')  
  
int_ch2 = hex_char2-55; //// A 的Ascll - 65  
  
else   
  
int_ch2 = hex_char2-87; //// a 的Ascll - 97  
  
   
  
int_ch = int_ch1+int_ch2;  
  
NSLog(@"int_ch=%d",int_ch);  
  
bytes[j] = int_ch;  ///将转化后的数放入Byte数组里  
  
j++;  
  
}  
  
NSData *newData = [[NSData alloc] initWithBytes:bytes length:128];  
  
NSLog(@"newData=%@",newData);  
  
   
  
3. NSData 与 UIImage  
  
NSData－>UIImage  
  
UIImage *aimage = [UIImage imageWithData: imageData];  
  
   
  
//例：从本地文件沙盒中取图片并转换为NSData  
  
NSString *path = [[NSBundle mainBundle] bundlePath];  
  
NSString *name = [NSString stringWithFormat:@"ceshi.png"];  
  
NSString *finalPath = [path stringByAppendingPathComponent:name];  
  
NSData *imageData = [NSData dataWithContentsOfFile: finalPath];  
  
UIImage *aimage = [UIImage imageWithData: imageData];  
  
   
  
UIImage－> NSData  
  
NSData *imageData = UIImagePNGRepresentation(aimae);