ios 开发小技巧总结

 1 1、如果在程序中想对某张图片进行处理的话（得到某张图片的一部分）可一用以下代码：
 2 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];


 3 2、判断设备是iphone还是iphone4的代码：
 4 #define isRetina ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 960), [[UIScreen mainScreen] currentMode].size) : NO)

 5 3、判断邮箱输入的是否正确：
 6 - (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];}
 7 4、如何把当前的视图作为照片保存到相册中去： #import <QuartzCore/QuartzCore.h>UIGraphicsBeginImageContext(currentView.bounds.size);     //currentView 当前的view[currentView.layer renderInContext:UIGraphicsGetCurrentContext()];UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);
 8 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];
}
 9 6、捕获iphone通话事件：

CTCallCenter *center = [[CTCallCenter alloc] init];

center.callEventHandler = ^(CTCall *call) {
　　NSLog(@"call:%@", call.callState);
}
10 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。
11 8、使UIimageView的图像旋转：
12 float rotateAngle = M_PI;CGAffineTransform transform =CGAffineTransformMakeRotation(rotateAngle);imageView.transform = transform;
13 9、设置旋转的原点： #import <QuartzCore/QuartzCore.h>UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"bg.png"]];imageView.layer.anchorPoint = CGPointMake(0.5, 1.0);
14 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];
15 [UIView beginAnimations:nil context:nil];[UIView setAnimationDuration:2];frame.origin.x += 150;[img setFrame:frame];[UIView commitAnimations];
16 11、在程序中实现电话的拨打：
17 //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]; 
18 //点击拨号按钮直接拨号 [btnPhone addTarget:self action:@selector(callAction:event:) forControlEvents:UIControlEventTouchUpInside]; 
19 [cell.contentView addSubview:btnPhone];  //cell是一个UITableViewCell 
20 //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 }
21 12、更改iphone的键盘颜色：
22 1.只有这2种数字键盘才有效果。UIKeyboardTypeNumberPad，UIKeyboardTypePhonePad2. 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];}}}
23 13、设置时区
24  NSTimeZone *defaultTimeZone = [NSTimeZone defaultTimeZone];NSTimeZone *tzGMT = [NSTimeZone timeZoneWithName:@"GMT"];[NSTimeZone setDefaultTimeZone:tzGMT];上面两个时区任意用一个。
25 14、Ipad隐藏键盘的同时触发方法。  [[NSNotificationCenter defaultCenter] addObserver:selfselector:@selector(keyboardWillHide:)name:UIKeyboardWillHideNotification  object:nil];
26 - (IBAction)keyboardWillHide:(NSNotification *)note
27 14、在一个程序中打开另一个程序的方法。 http://www.cocoachina.com/iphonedev/sdk/2010/0322/768.html15、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);}