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];
2、判断设备是iphone还是iphone4的代码：
#define isRetina ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640 , 960 ), [[UIScreen mainScreen] currentMode].size) : NO)
3、判断邮箱输入的是否正确：
- (BOOL ) validateEmail: (NSString *) candidate {
NSString *emailRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
NSPredicate *emailTest = [NSPredicate predicateWithFormat :@"SELF MATCHES %@" , emailRegex];
return [emailTest evaluateWithObject :candidate];
}
4、如何把当前的视图作为照片保存到相册中去：
#import
UIGraphicsBeginImageContext(currentView.bounds .size ); //currentView 当前的 view
[currentView. layer renderInContext: UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, nil , nil , nil );
5、本地通知（类似于push通知）按home键到后台 十秒后触发：
UILocalNotification *notification=[[UILocalNotification alloc ] init ];
if (notification!=nil ) {
NSLog ( @">> support local notification");
NSDate *now=[NSDate new ];
notification.fireDate =[now addTimeInterval :10 ];
notification.timeZone =[NSTimeZone defaultTimeZone ];
notification.alertBody =@" 该去吃晚饭了！ " ;
[[ UIApplication sharedApplication]. scheduleLocalNotification:notification];
}
6、捕获iphone通话事件：
CTCallCenter *center = [[CTCallCenter alloc ] init ];
center.callEventHandler = ^(CTCall *call )
{
NSLog (@"call:%@" , call .callState);
}
7、 iOS 4 引入了多任务支持，所以用户按下 “Home” 键以后程序可能并没有退出而是转入了后台运行。如果您想让应用直接退出，最简单的方法是：在 info－plist 里面找到 Application does not run in background 一项，勾选即可。
8、使UIimageView的图像旋转：
float rotateAngle = M_PI ;
CGAffineTransform transform =CGAffineTransformMakeRotation (rotateAngle);
imageView.transform = transform;
9、设置旋转的原点：
#import
UIImageView *imageView = [[UIImageView alloc ] initWithImage :[UIImage imageNamed :@"bg.png" ]];
imageView.layer.anchorPoint = CGPointMake (0.5 , 1.0 );
10、实现自定义的状态栏（遮盖状态栏）：
CGRect frame = {{0 , 0 }, {320 , 20 }};
UIWindow* wd = [[UIWindow alloc ] initWithFrame :frame];
[wd setBackgroundColor:[ UIColor clearColor]];
[wd setWindowLevel : UIWindowLevelStatusBar];
frame = CGRectMake (100 , 0 , 30 , 20 );
UIImageView* img = [[UIImageView alloc ] initWithFrame :frame];
[img setContentMode: UIViewContentModeCenter];
[img setImage:[ UIImage imageNamed: @"00_0103.png" ]];
[wd addSubview :img];
[wd makeKeyAndVisible];
[ UIView beginAnimations: nil context: nil ];
[ UIView setAnimationDuration: 2 ];
frame.origin.x += 150 ;
[img setFrame :frame];
[ UIView commitAnimations];
11、在程序中实现电话的拨打：
// 添加电话图标按钮
UIButton *btnPhone = [[ UIButton buttonWithType: UIButtonTypeCustom] retain];
btnPhone.frame = CGRectMake (280 ,10 ,30 ,30 );
UIImage *image = [UIImage imageNamed :@"phone.png" ];
[btnPhone setBackgroundImage:image forState: UIControlStateNormal];
// 点击拨号按钮直接拨号
[btnPhone addTarget: self action: @selector (callAction:event:) forControlEvents: UIControlEventTouchUpInside];
[cell. contentView addSubview :btnPhone]; //cell是一个 UITableViewCell
// 定义点击拨号按钮时的操作
- (void )callAction:(id )sender event:(id )event{
NSSet *touches = [event allTouches ];
UITouch *touch = [touches anyObject ];
CGPoint currentTouchPosition = [touch locationInView :self .listTable];
NSIndexPath *indexPath = [self .listTable indexPathForRowAtPoint : currentTouchPosition];
if (indexPath == nil ) {
return;
}
NSInteger section = [indexPath section ];
NSUInteger row = [indexPath row ];
NSDictionary *rowData = [datas objectAtIndex :row];
NSString *num = [[NSString alloc ] initWithFormat :@"tel://%@" ,number]; //number 为号码字符串
[[ UIApplication sharedApplication] openURL:[ NSURL URLWithString:num]]; // 拨号
}
12、更改iphone的键盘颜色：
1. 只有这 2种数字键盘才有效果。 UIKeyboardTypeNumberPad， UIKeyboardTypePhonePad
2. keyboardAppearance ＝ UIKeyboardAppearanceAlert
- (void )textViewDidBeginEditing:(UITextView *)textView{
NSArray *ws = [[ UIApplication sharedApplication] windows];
for (UIView *w in ws){
NSArray *vs = [w subviews ];
for (UIView *v in vs)
{
if ([[ NSString stringWithUTF8String: object_getClassName(v)] isEqualToString: @"UIKeyboard" ])
{
v. backgroundColor = [ UIColor redColor ];
}
}
}
13、设置时区
NSTimeZone *defaultTimeZone = [NSTimeZone defaultTimeZone ];
NSTimeZone *tzGMT = [ NSTimeZone timeZoneWithName : @"GMT" ];
[ NSTimeZone setDefaultTimeZone:tzGMT];
上面两个时区任意用一个。
14、Ipad隐藏键盘的同时触发方法。
[[ NSNotificationCenter defaultCenter] addObserver: self
selector :@selector (keyboardWillHide:)
name : UIKeyboardWillHideNotification
object :nil ];
- (IBAction )keyboardWillHide:(NSNotification *)note
14、在一个程序中打开另一个程序的方法。
/iphonedev/sdk/2010/0322/768.html
15、计算字符串的字数
-(int )calculateTextNumber:(NSString *)text
{
float number = 0.0 ;
int index = 0 ;
for (index; index < [text length ]; index++)
{
NSString *protoText = [text substringToIndex :[text length ] - index];
NSString *toChangetext = [text substringToIndex :[text length ] -1 -index];
NSString *charater;
if ([toChangetext length ]==0 )
{
charater = protoText;
}
else
{
NSRange range = [text rangeOfString :toChangetext];
charater = [protoText stringByReplacingCharactersInRange:range withString: @"" ];
}
NSLog (charater);
if ([charater lengthOfBytesUsingEncoding: NSUTF8StringEncoding] == 3 )
{
number++;
}
else
{
number = number+0.5 ;
}
}
return ceil (number);
}
http://www.cnblogs.com/java-time/archive/2011/05/23/tt139.html