iOS开发中常用代码解释

#include  /* 说明 malloc, NULL, size_t */
#include  /* 说明 va_ 相关类型和函数 */
#include  /* 说明 strcat 等 */
char *vstrcat(const char *first, ...)
{
size_t len;
char *retbuf;
va_list argp;
char *p;
if(first == NULL)
return NULL;
len = strlen(first);
va_start(argp, first);
while((p = va_arg(argp, char *)) != NULL)
len += strlen(p);
va_end(argp);
retbuf = malloc(len + 1); /* +1 包含终止符 \0 */
if(retbuf == NULL)
return NULL; /* 出错 */
(void)strcpy(retbuf, first);
va_start(argp, first); /* 重新开始扫描 */
while((p = va_arg(argp, char *)) != NULL)
(void)strcat(retbuf, p);
va_end(argp);
retbuf = malloc(len + 1); /* +1 包含终止符 \0 */
if(retbuf == NULL)
return NULL; /* 出错 */
(void)strcpy(retbuf, first);
va_start(argp, first); /* 重新开始扫描 */
while((p = va_arg(argp, char *)) != NULL)
(void)strcat(retbuf, p);
va_end(argp);
return retbuf;
}
 
%c 一个单一的字符
%d 一个十进制整数
%i 一个整数
%e, %f, %g 一个浮点数
%o 一个八进制数
%s 一个字符串
%x 一个十六进制数
%p 一个指针
%n 一个等于读取字符数量的整数
%u 一个无符号整数
%[] 一个字符集
%% 一个精度符号 
 
//一、NSString
    /*----------------创建字符串的方法----------------*/
 
    1、创建常量字符串。
    NSString *astring = @"This is a String!";
 
    2、创建空字符串，给予赋值。
    NSString *astring = [[NSString alloc] init];
    astring = @"This is a String!";
    NSLog(@"astring:%@",astring);
    [astring release];
 
    3、在以上方法中，提升速度:initWithString方法
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
    NSLog(@"astring:%@",astring);
    [astring release];
 
    4、用标准c创建字符串:initWithCString方法
    char *Cstring = "This is a String!";
    NSString *astring = [[NSString alloc] initWithCString:Cstring];
    NSLog(@"astring:%@",astring);
    [astring release];
 
    5、创建格式化字符串:占位符（由一个%加一个字符组成）
    int i = 1;
    int j = 2;
    NSString *astring = [[NSString alloc]
                        initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];
    NSLog(@"astring:%@",astring);
    [astring release];
 
    6、创建临时字符串
    NSString *astring;
    astring = [NSString stringWithCString:"This is a temporary string"];
    NSLog(@"astring:%@",astring);
 
    /*----------------从文件读取字符串:initWithContentsOfFile方法 ----------------*/
    NSString *path = @"astring.text";
    NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
    NSLog(@"astring:%@",astring);
    [astring release];
 
    /*----------------写字符串到文件:writeToFile方法 ----------------*/
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
    NSLog(@"astring:%@",astring);
    NSString *path = @"astring.text";
    [astring writeToFile: path atomically: YES];
    [astring release];    
 
    /*---------------- 比较两个字符串----------------*/
    用C比较:strcmp函数
    char string1[] = "string!";
    char string2[] = "string!";
    if(strcmp(string1, string2) = = 0)
    {
        NSLog(@"1");
    }
 
    isEqualToString方法
    NSString *astring01 = @"This is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 isEqualToString:astring02];
    NSLog(@"result:%d",result);
 
    compare方法(comparer返回的三种值)
    NSString *astring01 = @"This is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
    NSLog(@"result:%d",result);
    NSOrderedSame 判断两者内容是否相同
 
    NSString *astring01 = @"This is a String!";
    NSString *astring02 = @"this is a String!";
    BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
    NSLog(@"result:%d",result);
    //NSOrderedAscending 判断两对象值的大小(按字母顺序进行比较，astring02大于astring01为真)
 
    NSString *astring01 = @"this is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;
    NSLog(@"result:%d",result);
    //NSOrderedDescending 判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)
 
    不考虑大 小写比较字符串1
    NSString *astring01 = @"this is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
    NSLog(@"result:%d",result);
    //NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为 真)
 
    不考虑大小写比较字符串2
    NSString *astring01 = @"this is a String!";
    NSString *astring02 = @"This is a String!";
    BOOL result = [astring01 compare:astring02
                            options:NSCaseInsensitiveSearch | NSNumericSearch] = = NSOrderedSame;
    NSLog(@"result:%d",result);     
 
    //NSCaseInsensitiveSearch:不区分大小写比较 NSLiteralSearch:进行完全比较，区分大小写 NSNumericSearch:比较字符串的字符个数，而不是字符值。
 
    /*----------------改变字符串的大小写----------------*/
    NSString *string1 = @"A String";
    NSString *string2 = @"String";
    NSLog(@"string1:%@",[string1 uppercaseString]);//大写
    NSLog(@"string2:%@",[string2 lowercaseString]);//小写
    NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小
 
    /*----------------在串中搜索子串 ----------------*/
    NSString *string1 = @"This is a string";
    NSString *string2 = @"string";
    NSRange range = [string1 rangeOfString:string2];
    int location = range.location;
    int leight = range.length;
    NSString *astring = [[NSString alloc]
                        initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i"
                        ,location,leight]];
    NSLog(@"astring:%@",astring);
    [astring release];
 
    /*----------------抽取子串 ----------------*/
    -substringToIndex: 从字符串的开头一直截取到指定的位置，但不包括该位置的字符
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringToIndex:3];
    NSLog(@"string2:%@",string2);
 
    -substringFromIndex: 以指定位置开始（包括指定位置的字符），并包括之后的全部字符
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringFromIndex:3];
    NSLog(@"string2:%@",string2);
 
    -substringWithRange: //按照所给出的位置，长度，任意地从字符串中截取子串
    NSString *string1 = @"This is a string";
    NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
    NSLog(@"string2:%@",string2); 
 
const char *fieldValue = [value  cStringUsingEncoding:NSUTF8StringEncoding];
const char *fieldValue = [value UTF8String];
 
NSString 转 NSData
NSString* str= @"kilonet";
NSData* data=[str dataUsingEncoding:NSUTF8StringEncoding]; 
 
   Date format用法：
  -(NSString *) getDay:(NSDate *) d
{
    NSString *s ;
    NSDateFormatter *format = [[NSDateFormatter alloc] init];
    [format setDateFormat:@"YYYY/MM/dd hh:mm:ss"];
    s = [format stringFromDate:d];
    [format release];
    return s;
}
 
各地时区获取：
 
NSDate *nowDate = [NSDate new];
    NSDateFormatter *formatter    =  [[NSDateFormatter alloc] init];
    [formatter    setDateFormat:@"yyyy/MM/dd HH:mm:ss"];
    //    根据时区名字获取当前时间，如果该时区不存在，默认获取系统当前时区的时间
    //    NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:@"Europe/Andorra"];
    //    [formatter setTimeZone:timeZone];
    //获取所有的时区名字
    NSArray *array = [NSTimeZone knownTimeZoneNames];
    //    NSLog(@"array:%@",array);
    //for循环
    //    for(int i=0;i<[array count];i++)
    //    {
    //        NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:[array objectAtIndex:i]];
    //        [formatter setTimeZone:timeZone];
    //        NSString *locationTime = [formatter stringFromDate:nowDate];
    //        NSLog(@"时区名字:%@   : 时区当前时间: %@",[array objectAtIndex:i],locationTime);
    //        //NSLog(@"timezone name is:%@",[array objectAtIndex:i]);
    //    }
    //快速枚举法
    for(NSString *timeZoneName in array){
        [formatter setTimeZone:[NSTimeZone timeZoneWithName:timeZoneName]];
        NSLog(@"%@,%@",timeZoneName,[formatter stringFromDate:nowDate]);
    }
 
    [formatter release];
    [nowDate release];
 
 NSCalendar用法：
 
 -(NSString *) getWeek:(NSDate *) d {
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    unsigned units = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit | NSWeekdayCalendarUnit;
    NSDateComponents *components = [calendar components:units fromDate:d];
    [calendar release];
 
    switch ([components weekday]) {
        case 2:
            return @"Monday";
            break;
        case 3:
            return @"Tuesday";
            break;
        case 4:
            return @"Wednesday";
            break;
        case 5:
           return @"Thursday";
            break;
        case 6:
            return  @"Friday";
            break;
        case 7:
            return  @"Saturday";
            break;
        case 1:
            return @"Sunday";
            break;
        default:
            return @"No Week";
            break;
    }
 
    // 用components，我们可以读取其他更多的数据。
 
}
 
4. 用Get方式读取网络数据：
 
将网络数读取为字符串
- (NSString *) getDataByURL:(NSString *) url {
    return [[NSString alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]] encoding:NSUTF8StringEncoding];
}
 
//读取网络图片
- (UIImage *) getImageByURL:(NSString *) url {
    return [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]]];
}
 
多线程
[NSThread detachNewThreadSelector:@selector(scheduleTask) toTarget:self withObject:nil];
 
-(void) scheduleTask {
    //create a pool
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 
    //release the pool;
    [pool release];
}
 
//如果有参数，则这么使用：
[NSThread detachNewThreadSelector:@selector(scheduleTask:) toTarget:self withObject:[NSDate date]];
 
-(void) scheduleTask:(NSDate *) mdate {
    //create a pool
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 
    //release the pool;
    [pool release];
}
 
//注意selector里有冒号。
    //在线程里运行主线程里的方法 
 
    [self performSelectorOnMainThread:@selector(moveToMain) withObject:nil waitUntilDone:FALSE];
 
6. 定时器NSTimer用法:
 
代码
  // 一个可以自动关闭的Alert窗口
 
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil
                                                    message:[@"一个可以自动关闭的Alert窗口"
                                                   delegate:nil
                                          cancelButtonTitle:nil //NSLocalizedString(@"OK", @"OK")   //取消任何按钮
                                          otherButtonTitles:nil];
    //[alert setBounds:CGRectMake
      (alert.bounds.origin.x, alert.bounds.origin.y,
      alert.bounds.size.width, alert.bounds.size.height+30.0)];
    [alert show];
 
    UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
 
    // Adjust the indicator so it is up a few pixels from the bottom of the alert
    indicator.center = CGPointMake(alert.bounds.size.width/2,  alert.bounds.size.height-40.0);
    [indicator startAnimating];
    [alert insertSubview:indicator atIndex:0];
    [indicator release];
 
    [NSTimer scheduledTimerWithTimeInterval:3.0f
                                     target:self
                                   selector:@selector(dismissAlert:)
                                   userInfo:[NSDictionary dictionaryWithObjectsAndKeys:alert,
                   @"alert", @"testing ", @"key" ,nil]  //如果不用传递参数，那么可以将此项设置为nil.
                                    repeats:NO];
 
    NSLog(@"release alert");
    [alert release];
 
-(void) dismissAlert:(NSTimer *)timer{
 
    NSLog(@"release timer");
    NSLog([[timer userInfo]  objectForKey:@"key"]);
 
    UIAlertView *alert = [[timer userInfo]  objectForKey:@"alert"];
    [alert dismissWithClickedButtonIndex:0 animated:YES];
 
}
 
定时器停止使用：
 
[timer invalidate];
timer = nil;
 
     7. 用户缺省值NSUserDefaults读取：
 
    //得到用户缺省值
    NSUserDefaults *defs = [NSUserDefaults standardUserDefaults];
 
    //在缺省值中找到AppleLanguages, 返回值是一个数组
    NSArray* languages = [defs objectForKey:@"AppleLanguages"];
    NSLog(@"all language语言 is %@", languages);
 
    //在得到的数组中的第一个项就是用户的首选语言了
    NSLog(@"首选语言 is %@",[languages objectAtIndex:0]);  
 
    //get the language & country code
    NSLocale *currentLocale = [NSLocale currentLocale];
 
    NSLog(@"Language Code is %@", [currentLocale objectForKey:NSLocaleLanguageCode]);
    NSLog(@"Country Code is %@", [currentLocale objectForKey:NSLocaleCountryCode
 
8. View之间切换的动态效果设置：
 
    SettingsController *settings = [[SettingsController alloc]initWithNibName:@"SettingsView" bundle:nil];
    settings.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;  //水平翻转
    [self presentModalViewController:settings animated:YES];
    [settings release];
 
9.NSScrollView 滑动用法：
 
-(void) scrollViewDidScroll:(UIScrollView *)scrollView{
    NSLog(@"正在滑动中...");
}
 
//用户直接滑动NSScrollView，可以看到滑动条
-(void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
 
}
 
// 通过其他控件触发NSScrollView滑动，看不到滑动条
- (void) scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
 
}
 
    11.键盘处理系列
 
 //set the UIKeyboard to switch to a different text field when you press return
 
//switch textField to the name of your textfield
[textField becomeFirstResponder];
 
srandom(time(NULL)); //随机数种子
 
id d = random(); // 随机数
 
   4. iPhone的系统目录:
 
//得到Document目录：
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
 
//得到temp临时目录：
NSString *tempPath = NSTemporaryDirectory();
 
//得到目录上的文件地址：
NSString *文件地址 = [目录地址 stringByAppendingPathComponent:@"文件名.扩展名"];
 
 5. 状态栏显示Indicator：
 
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES; 
 
  6.app Icon显示数字：
 
- (void)applicationDidEnterBackground:(UIApplication *)application{
    [[UIApplication sharedApplication] setApplicationIconBadgeNumber:5];
}
 
   7.sqlite保存地址： 
 
代码
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *thePath = [paths objectAtIndex:0];
    NSString *filePath = [thePath stringByAppendingPathComponent:@"kilonet1.sqlite"];
 
    NSString *dbPath = [[[NSBundle mainBundle] resourcePath]
                        stringByAppendingPathComponent:@"kilonet2.sqlite"]; 
 
   8.Application退出：exit(0);
 
      9. AlertView，ActionSheet的cancelButton点击事件：
 
代码
-(void) actionSheet :(UIActionSheet *) actionSheet didDismissWithButtonIndex:(NSInteger) buttonIndex {
    NSLog(@"cancel actionSheet........");
    //当用户按下cancel按钮
    if( buttonIndex == [actionSheet cancelButtonIndex]) {
        exit(0);
    }
//    //当用户按下destructive按钮
//    if( buttonIndex == [actionSheet destructiveButtonIndex]) {
//        // DoSomething here.
//    }
}
 
- (void)alertView:(UIAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex {
     NSLog(@"cancel alertView........");
    if (buttonIndex == [alertView cancelButtonIndex]) {
        exit(0);
    }
}
 
  10.给Window设置全局的背景图片：
window.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"coolblack.png"]];
 
    11. UITextField文本框显示及对键盘的控制:
 
代码
#pragma mark -
#pragma mark UITextFieldDelegate
//控制键盘跳转
- (BOOL)textFieldShouldReturn:(UITextField *)textField {
 
    if (textField == _txtAccount) {
        if ([_txtAccount.text length]==0) {
            return NO;
        }
        [_txtPassword becomeFirstResponder];
    } else if (textField == _txtPassword) {
        [_txtPassword resignFirstResponder];
    }
 
    return YES;
}
 
//输入框背景更换
-(BOOL) textFieldShouldBeginEditing:(UITextField *)textField{
 
    [textField setBackground:[UIImage imageNamed:@"ctext_field_02.png"]];
 
    return YES;
}
 
-(void) textFieldDidEndEditing:(UITextField *)textField{
    [textField setBackground:[UIImage imageNamed:@"ctext_field_01.png"]];
}
 
12.UITextField文本框前面空白宽度设置以及后面组合按钮设置：
 
代码
    //给文本输入框后面加入空白
    _txtAccount.rightView = _btnDropDown;
    _txtAccount.rightViewMode =  UITextFieldViewModeAlways;
 
    //给文本输入框前面加入空白
    CGRect frame = [_txtAccount frame];
    frame.size.width = 5;
    UIView *leftview = [[UIView alloc] initWithFrame:frame];
    _txtAccount.leftViewMode = UITextFieldViewModeAlways;
    _txtAccount.leftView = leftview;
 
  13. UIScrollView 设置滑动不超出本身范围：
 
 [fcScrollView setBounces:NO]; 
 
 14. 在drawRect里画文字：
 
     UIFont * f = [UIFont systemFontOfSize:20]; 
 
    [[UIColor darkGrayColor] set]; 
 
    NSString * text = @"hi \nKiloNet"; 
 
    [text drawAtPoint:CGPointMake(center.x,center.y) withFont:f];
 
    15. NSArray查找是否存在对象时用indexOfObject,如果不存在则返回为NSNotFound.
 
    16. NString与NSArray之间相互转换：
 
array = [string componentsSeparatedByString:@","];
string = [[array valueForKey:@"description"] componentsJoinedByString:@","];
 
     17. TabController随意切换tab bar：
 
[self.tabBarController setSelectedIndex:tabIndex];
 
或者 self.tabBarController.selectedIndex = tabIndex;
 
或者实现下面的delegate来扑捉tab bar的事件： 
 
代码-(BOOL) tabBarController:(UITabBarController *)tabBarController
shouldSelectViewController:(UIViewController *)viewController
{        if ([viewController.tabBarItem.title isEqualToString: NSLocalizedString(@"Logout",nil)])
{        [self showLogout];        return NO;    }    return YES;}
 
    18. 自定义View之间切换动画：
代码
- (void) pushController: (UIViewController*) controller
         withTransition: (UIViewAnimationTransition) transition
{
    [UIView beginAnimations:nil context:NULL];
    [self pushViewController:controller animated:NO];
    [UIView setAnimationDuration:.5];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationTransition:transition forView:self.view cache:YES];
    [UIView commitAnimations];
}
 
CATransition *transition = [CATransition animation];
transition.duration = kAnimationDuration;
transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
transition.type = kCATransitionPush;
transition.subtype = kCATransitionFromTop;
transitioning = YES;
transition.delegate = self;
[self.navigationController.view.layer addAnimation:transition forKey:nil];
 
self.navigationController.navigationBarHidden = NO;
[self.navigationController pushViewController:tableViewController animated:YES];
 
     20.计算字符串长度：
 
CGFloat w = [title sizeWithFont:[UIFont fontWithName:@"Arial" size:18]].width; 
 
  23.在使用UISearchBar时，将背景色设定为clearColor，或者将translucent设为YES，都不能使背景透明，经过一番研究，发现了一种超级简单和实用的方法：
 
1
 [[searchbar.subviews objectAtIndex:0]removeFromSuperview]; 
 
背景完全消除了，只剩下搜索框本身了。 
 
  24.  图像与缓存 :
 
UIImageView *wallpaper = [[UIImageView alloc] initWithImage:
 
        [UIImage imageNamed:@"icon.png"]]; // 会缓存图片
 
UIImageView *wallpaper = [[UIImageView alloc] initWithImage:
 
        [UIImage imageWithContentsOfFile:@"icon.png"]]; // 不会缓存图片 
 
  25. iphone-常用的对视图图层(layer)的操作
 
对图层的操作：
 
(1.给图层添加背景图片：
myView.layer.contents = (id)[UIImage imageNamed:@"view_BG.png"].CGImage;
 
(2.将图层的边框设置为圆脚
myWebView.layer.cornerRadius = 8;
myWebView.layer.masksToBounds = YES;
 
(3.给图层添加一个有色边框
myWebView.layer.borderWidth = 5;
myWebView.layer.borderColor = [[UIColor colorWithRed:0.52 green:0.09 blue:0.07 alpha:1] CGColor];