1，获取翻转事件，并开启翻转：

只要在viewcontroller的类中加入

-(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation{

//翻转后要执行的代码

return YES;

}

2，-(void)viewWillAppear:(BOOL)animated，- (void)viewDidLoad 的区别。

viewwillappear是每次视图控制器的视图出现前执行的代码。而viewdidload是每次视图控制器载入是执行的代码。

比如说：当a视图控制器的视图第一次出现是两个都要执行，但当a被push后有pop回来时，只有viewwillappear执行。

3，如何让视图始终跟着手指移动，并有反弹事件

xsum=photopositon.origin.x+photopositon.size.width/2-touchstart.x;

ysum=photopositon.origin.y+photopositon.size.height/2-touchstart.y;

currentview.center=CGPointMake(xsum+p.x, ysum+p.y);

if (pow(currentview.center.x-160,2.0)>pow(photopositon.size.width/2,2.0)||

pow(currentview.center.y-240,2.0)>pow(photopositon.size.height/2, 2.0))

{

[UIView beginAnimations:nil context:NULL];

[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];

[UIView setAnimationDuration:0.3];

currentview.center=CGPointMake(160, 240);

[UIView commitAnimations];

}

就是让currentview的视图中心始终与手指保持一定的方位。

4，控制导航条和toolbar

[self.navigationController   ...］

[self.navigationController.toolbar  ...］

比如说让他们都消失：

[self.navigationController setToolbarItems:NULL animated:YES];

[self.navigationController.toolbar setBarStyle:UIBarStyleBlackTranslucent];

[self.navigationController setToolbarHidden:NO animated:YES];

5，自定义控件事件：

addTarget:self action:@selector(....) forControlEvents:....

比如获取某个按钮的触摸事件；

[new addTarget:self action:@selector(onChooseItem:) forControlEvents:UIControlEventTouchUpInside]

则当按钮按下时，- (void)onChooseItem:(id) sender 就会被调用。

sender传的就是被按下按钮的指针。

6.获取文件的路径，即获取documents的路径

    //获取文件路径    NSArray *path=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *documentsPath=[path objectAtIndex:0];

NSLog(@"%@",documentsPath);

补充：

1. NSSearchPathForDirectoriesInDomains和NSHomeDirectory    iPhone和symbian 3rd一样，会为每一个应用程序生成一个私有目录，这个目录位于/Users/sundfsun2009/Library/Application Support/iPhone         Simulator/User/Applications下，并随即生成一个数字字母串作为目录名，在每一次应用程序启动时，这个字母数字串都是不同于上一次。

    通常使用Documents目录进行数据持久化的保存，而这个Documents目录可以通过 NSSearchPathForDirectoriesInDomains（NSDocumentDirectory，NSUserdomainMask，YES） 得到，代码如下：

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *documentsDirectory = [paths objectAtIndex:0];

// NSString *path = [documentsDirectory stringByAppendingPathComponent:@"aa.plist"];

    NSLog(@"path:   %@",path);

    打印结果如下：

    path:   /Users/apple/Library/Application Support/iPhone Simulator/4.3/Applications/550AF26D-174B-42E6-881B-B7499FAA32B7/Documents

    而这个目录还可以通过 NSHomeDirectory()来得到，代码如下：

    NSString *destPath = NSHomeDirectory();    NSLog(@"path:   %@",destPath);//destPath = [destPath stringByAppendingPathComponent: @"Documents"];//NSString *xmlpath = [destPath stringByAppendingPathComponent: @"menu/menu.xml"];

    打印结果如下：

    path:   /Users/apple/Library/Application Support/iPhone Simulator/4.2/Applications/6F4BC466-C5D6-440C-BAAC-BE20FA468C61

    看看两者打印出来的结果，我们可以看出这两种方法的不同。

2. 浏览document下所有图片资源

#define DOCUMENTS_FOLDER [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]    NSArray *fileList = [[[NSFileManager defaultManager] directoryContentsAtPath:DOCUMENTS_FOLDER]                pathsMatchingExtensions:[NSArray arrayWithObject:@"png"]] ;

3. 得到图片中的某一部分：

    UIImage *image = [UIImage imageNamed:filename];    CGImageRef imageRef = image.CGImage;

    CGRect rect = CGRectMake(origin.x, origin.y ,size.width, size.height);

    CGImageRef imageRefRect = CGImageCreateWithImageInRect(imageRef, rect);

    UIImage *imageRect = [[UIImage alloc] initWithCGImage:imageRefRect];

7.在documents的路径下创建文件。

首先要获取documents的路径，如上第6条。

其次就是下面的语句了：

NSString *writePath=[NSString stringWithFormat:@"%@/%@.txt",documentsPath,@"aaa"];NSData *data = [@"" dataUsingEncoding:NSUTF8StringEncoding];//新文件的初始数据，设为空[[NSFileManager defaultManager] createFileAtPath:writePath contents:data attributes:nil];//创建文件的命令在这里

这样就可以在documents文件夹下创建一个aaa.txt的文件了。哈哈哈哈哈。

或者是用下面的语句，

NSString *writePath=[NSString stringWithFormat:@"%@/%@.txt",documentsDirectory,@"bbb"];NSError *error;[@"fasdfasdasddaa" writeToFile:writePath atomically:YES encoding:NSUTF8StringEncoding error:&error];

这样就可以在documents文件夹下创建一个bbb.txt的文件了。并且，文件中的有"fasdfasdasddaa"字符。

总结起来就是，先给要存储的东西取一个名字，然后，找到它的路径。然后以这个名字创建。创建的时候可以添加内容。

当然，图片也可以批量的生成，假如说让你把一张图片复制500遍，并且给他按照（1－500）重命名。

你可以用上面的方法，用一个循环批量的生成500张图片。

    UIImage *image = [UIImage imageNamed:@"240*360.png"];    NSData *data = UIImagePNGRepresentation(image);    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];    NSMutableArray *muArray;    NSString *filePath = nil;for (int j = 1; j<=500; j++) {        filePath = [[NSString alloc] initWithFormat:@"%@/%d.png",documentPath,j];        [data writeToFile:filePath atomically:YES];        NSString *newPath = [[NSString alloc] initWithFormat:@"%@",documentPath];        muArray = [[NSMutableArray alloc] initWithContentsOfFile:newPath];        [muArray addObject:filePath];        [filePath release];

｝

7.iphone开发中随机数的产生。

// Get random number between 0 and 99 int x = arc4random() % 81; // Get random number between 500 and 999 int y = ((arc4random()%501)+500);

NSLog(@"0－－99之间的随机数%d",x);NSLog(@"500－－999之间的随机数%d",y);

8.好看的文字处理

以tableView中cell的textLabel为例子：

    cell.backgroundColor  = [UIColor scrollViewTexturedBackgroundColor];//设置文字的字体    cell.textLabel.font = [UIFont fontWithName:@"American Typewriter" size:100.0f];//设置文字的颜色    cell.textLabel.textColor = [UIColor orangeColor];//设置文字的背景颜色    cell.textLabel.shadowColor = [UIColor whiteColor];//设置文字的显示位置    cell.textLabel.textAlignment = UITextAlignmentCenter;

9.新手学习webview

//Web view//A basic UIWebView. 

CGRect webFrame = CGRectMake(0.0, 0.0, 320.0, 460.0); UIWebView *webView = [[UIWebView alloc] initWithFrame:webFrame]; [webView setBackgroundColor:[UIColor whiteColor]]; NSString *urlAddress = @"http://www.google.com"; NSURL *url = [NSURL URLWithString:urlAddress];NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; [webView loadRequest:requestObj];[self addSubview:webView]; [webView release]

10。———————-隐藏Status Bar—————————–
读者可能知道一个简易的方法,那就是在程序的viewDidLoad中加入

[[UIApplication sharedApplication] setStatusBarHidden:YES animated:NO];

13。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。

UITextInputTraits属性

autocapitalizationType            设置键盘自动大小写的属性     UITextAutocapitalizationTypeNone 
autocorrectionType  property  设置是否有自动修改提示   UITextAutocorrectionTypeNo
enablesReturnKeyAutomatically   Boolean值－设置在用户没有输入是returnKey禁用，默认值NO
keyboardAppearance  设置键盘显示方式  除了默认模式  还有一个UIKeyboardAppearanceAlert模式
keyboardType               设置键盘类型   UIKeyboardTypePhonePad 等
returnKeyType              设置renturnKey按键上的提示文字     UIReturnKeyGo   UIReturnKeyNext
secureTextEntry           BOOL值  －－ 设置是否是密码保护模式输入

如下：
设置登录用的 输入框 UITextField
用户名输入框：
m_TF_username = [[UITextField alloc] initWithFrame:my_frame];
m_TF_username.borderStyle = UITextBorderStyleNone;
m_TF_username.clearButtonMode = UITextFieldViewModeWhileEditing;
m_TF_username.delegate = self;
m_TF_username.returnKeyType = UIReturnKeyNext;
m_TF_username.autocapitalizationType = UITextAutocapitalizationTypeNone;
[m_TF_username becomeFirstResponder];
密码输入框：
m_TF_password = [[UITextField alloc] initWithFrame:my_frame];
m_TF_password.borderStyle = UITextBorderStyleNone;
m_TF_password.clearButtonMode = UITextFieldViewModeWhileEditing;
m_TF_password.delegate = self;
m_TF_password.returnKeyType = UIReturnKeyGo;
m_TF_password.secureTextEntry =YES;

键盘透明
textField.keyboardAppearance = UIKeyboardAppearanceAlert;

状态栏的网络活动风火轮是否旋转
[UIApplication sharedApplication].networkActivityIndicatorVisible，默认值是NO。

截取屏幕图片
//创建一个基于位图的图形上下文并指定大小为CGSizeMake(200,400)
UIGraphicsBeginImageContext(CGSizeMake(200,400));

//renderInContext 呈现接受者及其子范围到指定的上下文
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
   
 //返回一个基于当前图形上下文的图片
 UIImage *aImage = UIGraphicsGetImageFromCurrentImageContext();
 
 //移除栈顶的基于当前位图的图形上下文
UIGraphicsEndImageContext();

//以png格式返回指定图片的数据
imageData = UIImagePNGRepresentation(aImage);

更改cell选中的背景
    UIView *myview = [[UIView alloc] init];
    myview.frame = CGRectMake(0, 0, 320, 47);
    myview.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"0006.png"]];
    cell.selectedBackgroundView = myview;

在数字键盘上添加button：
//定义一个消息中心
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil]; //addObserver:注册一个观察员 name:消息名称
- (void)keyboardWillShow:(NSNotification *)note {
    // create custom button
    UIButton *doneButton = [UIButton buttonWithType:UIButtonTypeCustom];
    doneButton.frame = CGRectMake(0, 163, 106, 53);
    [doneButton setImage:[UIImage imageNamed:@"5.png"] forState:UIControlStateNormal];
    [doneButton addTarget:self action:@selector(addRadixPoint) forControlEvents:UIControlEventTouchUpInside];
    
    // locate keyboard view
    UIWindow* tempWindow = [[[UIApplication sharedApplication] windows] objectAtIndex:1];//返回应用程序window
    UIView* keyboard;
    for(int i=0; i<[tempWindow.subviews count]; i++) //遍历window上的所有subview
    {
        keyboard = [tempWindow.subviews objectAtIndex:i];
        // keyboard view found; add the custom button to it
        if([[keyboard description] hasPrefix:@"<UIKeyboard"] == YES)
        [keyboard addSubview:doneButton];
    }
}

正则表达式使用：
被用于正则表达式的字串必须是可变长的，不然会出问题

将一个空间放在视图之上
[scrollView insertSubview:searchButton aboveSubview:scrollView];

从本地加载图片
NSString *boundle = [[NSBundle mainBundle] resourcePath];
[web1 loadHTMLString:[NSString stringWithFormat:@"<img src='http://fei263.blog.163.com/blog/0001.png'/>"] baseURL:[NSURL fileURLWithPath:boundle]];

从网页加载图片并让图片在规定长宽中缩小
[cell.img loadHTMLString:[NSString stringWithFormat:@"<html><body><img src='http://fei263.blog.163.com/blog/%@' height='90px' width='90px'></body></html>",goodsInfo.GoodsImg] baseURL:nil];
将网页加载到webview上通过javascript获取里面的数据，如果只是发送了一个连接请求获取到源码以后可以用正则表达式进行获取数据
NSString *javaScript1 = @"document.getElementsByName('.u').item(0).value";
NSString *javaScript2 = @"document.getElementsByName('.challenge').item(0).value";
NSString *strResult1 = [NSString stringWithString:[theWebView stringByEvaluatingJavaScriptFromString:javaScript1]];
NSString *strResult2 = [NSString stringWithString:[theWebView stringByEvaluatingJavaScriptFromString:javaScript2]];

用NSString怎么把UTF8转换成unicode
utf8Str //
NSString *unicodeStr = [NSString stringWithCString:[utf8Str UTF8String] encoding:NSUnicodeStringEncoding];

View自己调用自己的方法:
[self performSelector:@selector(loginToNext) withObject:nil afterDelay:2];//黄色段为方法名,和延迟几秒执行.

显示图像:
CGRect myImageRect = CGRectMake(0.0f, 0.0f, 320.0f, 109.0f); 
UIImageView *myImage = [[UIImageView alloc] initWithFrame:myImageRect];
[myImage setImage:[UIImage imageNamed:@"myImage.png"]]; 
myImage.opaque = YES; //opaque是否透明
[self.view addSubview:myImage]; 
[myImage release];

WebView:
CGRect webFrame = CGRectMake(0.0, 0.0, 320.0, 460.0); 
UIWebView *webView = [[UIWebView alloc] initWithFrame:webFrame]; 
[webView setBackgroundColor:[UIColor whiteColor]]; 
NSString *urlAddress = @"http://www.google.com"; 
NSURL *url = [NSURL URLWithString:urlAddress];
NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; 
[webView loadRequest:requestObj];
[self addSubview:webView]; 
[webView release];

显示网络活动状态指示符
这是在iPhone左上部的状态栏显示的转动的图标指示有背景发生网络的活动。
UIApplication* app = [UIApplication sharedApplication]; 
app.networkActivityIndicatorVisible = YES;

动画:一个接一个地显示一系列的图象
NSArray *myImages = [NSArray arrayWithObjects: [UIImage imageNamed:@"myImage1.png"], [UIImage imageNamed:@"myImage2.png"], [UIImage imageNamed:@"myImage3.png"], [UIImage imageNamed:@"myImage4.gif"], nil];
UIImageView *myAnimatedView = [UIImageView alloc]; 
[myAnimatedView initWithFrame:[self bounds]]; 
myAnimatedView.animationImages = myImages; //animationImages属性返回一个存放动画图片的数组
myAnimatedView.animationDuration = 0.25; //浏览整个图片一次所用的时间
myAnimatedView.animationRepeatCount = 0; // 0 = loops forever 动画重复次数
[myAnimatedView startAnimating]; 
[self addSubview:myAnimatedView]; 
[myAnimatedView release];

动画:显示了something在屏幕上移动。注：这种类型的动画是“开始后不处理” -你不能获取任何有关物体在动画中的信息(如当前的位置) 。如果您需要此信息，您会手动使用定时器去调整动画的X和Y坐标
这个需要导入QuartzCore.framework
CABasicAnimation *theAnimation; 
theAnimation=[CABasicAnimation animationWithKeyPath:@"transform.translation.x"]; 
//Creates and returns an CAPropertyAnimation instance for the specified key path.
//parameter:the key path of the property to be animated
theAnimation.duration=1; 
theAnimation.repeatCount=2; 
theAnimation.autoreverses=YES; 
theAnimation.fromValue=[NSNumber numberWithFloat:0]; 
theAnimation.toValue=[NSNumber numberWithFloat:-60]; 
[view.layer addAnimation:theAnimation forKey:@"animateLayer"];

Draggable items//拖动项目
Here's how to create a simple draggable image.//这是如何生成一个简单的拖动图象
1. Create a new class that inherits from UIImageView 
@interface myDraggableImage : UIImageView { } 
2. In the implementation for this new class, add the 2 methods: 
- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event 
{ 
// Retrieve the touch point 检索接触点
CGPoint pt = [[touches anyObject] locationInView:self]; 
startLocation = pt; 
[[self superview] bringSubviewToFront:self]; 
}
- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{ 
// Move relative to the original touch point 相对以前的触摸点进行移动
CGPoint pt = [[touches anyObject] locationInView:self]; 
CGRect frame = [self frame]; 
frame.origin.x += pt.x - startLocation.x; 
frame.origin.y += pt.y - startLocation.y; 
[self setFrame:frame]; 
} 
3. Now instantiate the new class as you would any other new image and add it to your view 
//实例这个新的类,放到你需要新的图片放到你的视图上
dragger = [[myDraggableImage alloc] initWithFrame:myDragRect]; 
[dragger setImage:[UIImage imageNamed:@"myImage.png"]]; 
[dragger setUserInteractionEnabled:YES];

线程:
1. Create the new thread: 
[NSThread detachNewThreadSelector:@selector(myMethod) toTarget:self withObject:nil]; 
2. Create the method that is called by the new thread: 
- (void)myMethod
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; 
*** code that should be run in the new thread goes here ***
[pool release]; 
} 
//What if you need to do something to the main thread from inside your new thread (for example, show a loading //symbol)? Use performSelectorOnMainThread.
[self performSelectorOnMainThread:@selector(myMethod) withObject:nil waitUntilDone:false];

Plist files
Application-specific plist files can be stored in the Resources folder of the app bundle. When the app first launches, it should check if there is an existing plist in the user's Documents folder, and if not it should copy the plist from the app bundle. 
// Look in Documents for an existing plist file
NSArray *paths = NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *documentsDirectory = [paths objectAtIndex:0]; 
myPlistPath = [documentsDirectory stringByAppendingPathComponent: 
[NSString stringWithFormat: @"%@.plist", plistName] ]; 
[myPlistPath retain]; 
// If it's not there, copy it from the bundle 
NSFileManager *fileManger = [NSFileManager defaultManager]; 
if ( ![fileManger fileExistsAtPath:myPlistPath] ) 
{ 
NSString *pathToSettingsInBundle = [[NSBundle mainBundle] pathForResource:plistName ofType:@"plist"]; 
} 
//Now read the plist file from Documents 
NSArray *paths = NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *documentsDirectoryPath = [paths objectAtIndex:0]; 
NSString *path = [documentsDirectoryPath stringByAppendingPathComponent:@"myApp.plist"]; 
NSMutableDictionary *plist = [NSDictionary dictionaryWithContentsOfFile: path];
//Now read and set key/values 
myKey = (int)[[plist valueForKey:@"myKey"] intValue]; 
myKey2 = (bool)[[plist valueForKey:@"myKey2"] boolValue]; 
[plist setValue:myKey forKey:@"myKey"]; 
[plist writeToFile:path atomically:YES];

Alerts
Show a simple alert with OK button. 
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:
@"An Alert!" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; 
[alert show]; 
[alert release];

Info button
Increase the touchable area on the Info button, so it's easier to press. 
CGRect newInfoButtonRect = CGRectMake(infoButton.frame.origin.x-25, infoButton.frame.origin.y-25, infoButton.frame.size.width+50, infoButton.frame.size.height+50); 
[infoButton setFrame:newInfoButtonRect];

Detecting Subviews
You can loop through subviews of an existing view. This works especially well if you use the "tag" property on your views.
for (UIImageView *anImage in [self.view subviews])
{
if (anImage.tag == 1) 
        { // do something } 
}

16.

//UILabel 和字体大小的匹配，可以用到制作电子书的时候。

    //UILabel 和字体大小的匹配，可以用到制作电子书的时候。    NSString *str = @"UILabel 和字体大小的匹配.亲爱的,在一起的日子很平淡，似乎波澜不惊，只是，这种平凡的日子是最浪漫的，对吗？遇到你之前，世界像一片荒草原；遇到你之后，世界像一个游乐园。过去的许多岁月，对我来说像一缕轻烟，未来的无限生涯，因你而幸福无边。爱一个人是在夜里等待另一个人的呼吸,虽然隔着千里万里,但我知道你在手机的那一端,于是我便会夜夜等待.守株待兔是人间最大的幸福,因为我有目标，你就是我要逮那只兔子,是我一生要好好照顾保护那个人.没有你的时候，你就是我的世界；和你在一起时，世界就是你的。亲爱的，情人节快乐。";    UIFont *font = [UIFont fontWithName:@"Arial" size:36.0f];    CGSize size = CGSizeMake(320, 2000);

    UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];//先设为“0”的大小状态    label.numberOfLines = 0;//当设为0的时候，label显示多行。

    CGSize labelSize = [str sizeWithFont:font constrainedToSize:size lineBreakMode:UILineBreakModeWordWrap];//得到size的宽和高    NSLog(@"%f",labelSize.height);    label.frame = CGRectMake(0, 0, labelSize.width, labelSize.height);    label.text = str;    label.font = font;    label.textColor = [UIColor blueColor];    [self.view addSubview:label];

    [label release];

17.选中某一行的时候，该行颜色变化

[tableView deselectRowAtIndexPath:indexPath animated:NO];//选择当前行，使得改行颜色变化，选中后的反显颜色即刻消失。

18.ios 音频后台播放

在按Home的情况下，后台如何播放音乐？

在Info.plist增加一项 Required backgroound modes默然是数组，在其下增加一个元素App plays audio

之后在代码中添加：

[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: nil];[[AVAudioSession sharedInstance] setActive:YES error: nil];

或者是下面的代码：

        AVAudioSession *session = [AVAudioSession sharedInstance];          [session setActive:YES error:nil];          [session setCategory:AVAudioSessionCategoryPlayback error:nil];11:47:36

放到初始化的中或在播放音乐前的即可。

19。数组排序

for (int j=0;j<[arr count];j++)    {for (int i=0; i<[arr count]-1-j; i++) {if ([[arr objectAtIndex:i] intValue]>[[arr objectAtIndex:i+1] intValue]) {                aa = [arr objectAtIndex:i+1];                [arr replaceObjectAtIndex:i+1 withObject:[arr objectAtIndex:i]];                [arr replaceObjectAtIndex:i withObject:aa];

            }        }    }

或者这样。。。。。。。。

//对数组进行排序-(void)paixuForArray:(NSMutableArray *)_array{    NSString *aa;    for (int j=0;j<[_array count];j++)    {        for (int i=0; i<[_array count]-1-j; i++) {            if ([[[_array objectAtIndex:i] substringWithRange:NSMakeRange(3, 4)] intValue]<[[[_array objectAtIndex:i+1] substringWithRange:NSMakeRange(3, 4)] intValue]) {                aa = [_array objectAtIndex:i+1];                [_array replaceObjectAtIndex:i+1 withObject:[_array objectAtIndex:i]];                [_array replaceObjectAtIndex:i withObject:aa];

            }        }    }

}

20。获取当前的日期，时间，星期几

    NSDate *date = [NSDate date];    NSCalendar *calendar = [NSCalendar currentCalendar];    NSDateComponents *comps;

// 年月日获得    comps = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)                         fromDate:date];    NSInteger year = [comps year];    NSInteger month = [comps month];    NSInteger day = [comps day];    NSLog(@"year: %d month: %d, day: %d", year, month, day);

//当前的时分秒获得    comps = [calendar components:(NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit)                        fromDate:date];    NSInteger hour = [comps hour];    NSInteger minute = [comps minute];    NSInteger second = [comps second];    NSLog(@"hour: %d minute: %d second: %d", hour, minute, second);

// 周几和星期几获得    comps = [calendar components:(NSWeekCalendarUnit | NSWeekdayCalendarUnit | NSWeekdayOrdinalCalendarUnit)                        fromDate:date];    NSInteger week = [comps week]; // 今年的第几周    NSInteger weekday = [comps weekday]; // 星期几（注意，周日是“1”，周一是“2”。。。。）    NSInteger weekdayOrdinal = [comps weekdayOrdinal]; // 这个月的第几周    NSLog(@"week: %d weekday: %d weekday ordinal: %d", week, weekday, weekdayOrdinal);

参考相关文章介绍，下面两篇文章介绍的很像细。http://www.2cto.com/kf/201202/118985.htmlhttp://www.cppblog.com/walkklookk/archive/2011/09/15/155852.aspx

21。

iPhone随机数

@interface UINavigationBar (ImageBackground) @end @implementation UINavigationBar (ImageBackground) - (void) drawRect:(CGRect)rect {     [[UIImage imageNamed:@"bkimage.png"] drawInRect:rect]; } @end