iphone develop tips

一些iphone的小細節，小技巧
1.時間戳記
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NSTimeInterval interval = [[NSDate date] timeIntervalSince1970];  
NSString* timeStamp = [NSString stringWithFormat:@"hex=%x,dec=%d,milSec=%.3f",(NSInteger)interval,(NSInteger)interval,interval];  

timeStamp 結果：
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hex=4fd7fd8a,dec=1339555210,milSec=1339555210.191  
2.UIView圓角實現
包含QuartzCore.framework ，然後包含標頭檔#import <QuartzCore/QuartzCore.h>
使用以下的 兩行代碼既可。
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tmpView.layer.cornerRadius  = 10.0;  
tmpView.layer.masksToBounds = YES;  
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UIView* tmpView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];  
tmpView.backgroundColor = [UIColor grayColor];  
tmpView.layer.cornerRadius  = 10.0;  
tmpView.layer.masksToBounds = YES;  
[self.view addSubview:tmpView];  
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設定邊框顏色，
UIView* view = [[UIView alloc] initWithFrame:CGRectZero];
view.layer.borderWidth = 1.0;
view.layer.borderColor = [UIColor redColor].CGColor;

3.用圖片平鋪做背景
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UIView* tmpView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];  
tmpView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"bg.png"]];  

4.用圖片展開做背景
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UIImageView* tmpView2 = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];  
tmpView2.image = [UIImage imageNamed:@"bg.png"];  

UIImageView 的ContentMode預設是 UIViewContentModeScaleToFill，即展開，可以選擇置中，靠左對齊，靠右對齊來不展開顯示。
5.使用UIView的transform屬性做旋轉等動畫，在使用完成後需要重新設定transform為預設 CGAffineTransformIdentity，否則下次setframe等操作時，現實錯誤。
6.使用UILabel時，設定setFrame需要保證CGrect 的值未整數，不能為浮點，否則系統自動做 消除鋸齒，現實模糊。圖片存在同樣問題。
7.播放gif動畫
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CGRect frameRect = CGRectZero;  
frameRect.size = [UIImage imageNamed:@"callshow_2.gif"].size;  
NSString*gifPath = [[NSBundle mainBundle] pathForResource:@"callshow_2" ofType:@"gif"];  
NSData* gifData = [NSData dataWithContentsOfFile:gifPath];  
UIWebView* webView = [[UIWebView alloc] initWithFrame:frameRect];  
[webView loadData:gifData MIMEType:@"image/gif" textEncodingName:nil baseURL:nil];  
[self.view addSubview:webView];  
8.隱藏tabbar之後，底部出現一個白條，去除方法

http://stackoverflow.com/questions/1982172/iphone-is-it-possible-to-hide-the-tabbar

隱藏：
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CGRect bounds = [[UIScreen mainScreen] bounds];  
CGRect tabBarFrame = self.tabBarController.tabBar.frame;  
  
self.tabBarController.view.frame = CGRectMake(0,0,bounds.size.width,bounds.size.height+tabBarFrame.size.height);  
self.tabBarController.tabBar.hidden = YES;  
顯示：
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CGRect bounds = [[UIScreen mainScreen] bounds];  
self.tabBarController.view.frame = CGRectMake(0,0,bounds.size.width,bounds.size.height);      
self.tabBarController.tabBar.hidden = NO;  

9.在導覽列中間加入segmentedControl，
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NSArray *segmentedArray = [[NSArray alloc]initWithObjects:@"111",@"222",nil];    
UISegmentedControl *segmentedControl = [[UISegmentedControl alloc] initWithItems:segmentedArray];    
segmentedControl.frame = CGRectMake(80, 0, 160.0, 30.0);  
segmentedControl.selectedSegmentIndex = 0;  
segmentedControl.segmentedControlStyle = UISegmentedControlStyleBar;  
[segmentedControl addTarget:self action:@selector(segmentButtonPressed:) forControlEvents:UIControlEventTouchUpInside];  
self.navigationItem.titleView = segmentedControl;  

其中 self.navigationItem.titleView 表示導覽列中間的view，另外，如果左右兩邊分別也有UIBarButtonItem，通過 self.navigationItem.leftBarButtonItem  和 self.navigationItem.rightBarButtonItem 來引用。
10，根據地址查看對應符號和地址
dwarfdump --lookup 0x0000641c -arch armv6 EmergencyNumbers.app.dSYM

11.動態設定UITextField是否安全輸入
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NSString* pass = passWordTextField_.text;  
passWordTextField_.enabled = NO;  
passWordTextField_.secureTextEntry = !isShowPassWord_;  
passWordTextField_.enabled = YES;  
[passWordTextField_ becomeFirstResponder];  
passWordTextField_.text = pass;  

11,點擊事件穿透父視圖，讓子圖響應事件
參考：http://cocoaheads.tumblr.com/post/2130871776/ignore-touches-to-uiview-subclass-but-not-to-its
要將父視圖的userInteractionEnabled 設為 YES
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-(id)hitTest:(CGPoint)point withEvent:(UIEvent *)event {  
    id hitView = [super hitTest:point withEvent:event];  
    if (hitView == self) return nil;  
    else return hitView;  
}  

12，讓視圖只響應 某個地區的點擊事件，利用11中提到方法
以下代碼實現讓view只響應CGRectMake(0, 0, 160, 40) 地區的事件
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- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event  
{  
    id hitView = [super hitTest:point withEvent:event];  
    if (hitView == self &&!CGRectContainsPoint(CGRectMake(0, 0, 160, 40), point))   
    {  
        NSLog(@">>>point=%@",NSStringFromCGPoint(point));  
        return nil;  
    }  
    else   
        return hitView;  
}  

13，螢幕
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CGContextRef context = UIGraphicsGetCurrentContext();  
// check if UIGraphicsBeginImageContextWithOptions is available (iOS is 4.0+)  
if (UIGraphicsBeginImageContextWithOptions != NULL)  
    UIGraphicsBeginImageContextWithOptions(size,NO,0.0);  
else  
    // iOS is < 4.0   
    UIGraphicsBeginImageContext(size);  
[self.layer renderInContext:context];  
UIImage* image = UIGraphicsGetImageFromCurrentImageContext();  
UIGraphicsEndImageContext();  
//然後將該圖片儲存到圖片圖  
UIImageWriteToSavedPhotosAlbum(image,self,nil,nil);  

14，由顏色產生圖片
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CGContextRef context = UIGraphicsGetCurrentContext();  
// check if UIGraphicsBeginImageContextWithOptions is available (iOS is 4.0+)  
if (UIGraphicsBeginImageContextWithOptions != NULL)  
    UIGraphicsBeginImageContextWithOptions(size,NO,0.0);  
else  
    // iOS is < 4.0   
    UIGraphicsBeginImageContext(size);  
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);  
CGContextFillRect(context, rect);  
UIImage* image = UIGraphicsGetImageFromCurrentImageContext();  
UIGraphicsEndImageContext();  

15.UIImageView 點擊效果

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UIImageView *imgView =[[UIImageView alloc] initWithFrame:CGRectMake(0, 0,320, 44)];  
imgView.userInteractionEnabled=YES;  
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleTap:)];  
[singleTap setNumberOfTapsRequired:1];  
[imgView addGestureRecognizer:singleTap];  
[singleTap release];  
16. 移動游標到末尾
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UITextView * m_textInput;  
//設定游標到輸入文字的末尾  
NSUInteger length = m_textInput.text.length;  
m_textInput.selectedRange = NSMakeRange(length,0);    

17.Xcode添加doxygen注釋

http://blog.chukong-inc.com/index.php/2012/05/16/xcode4_fast_doxygen/

http://blog.csdn.net/ch_soft/article/details/7633300

18 UIColor 反色
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+ (UIColor*)reverseColor:(UIColor*)color  
{  
    const CGFloat *componentColors = CGColorGetComponents(color.CGColor);  
    return [UIColor colorWithRed:(255 - componentColors[0])  
                           green:(255 - componentColors[1])  
                            blue:(255 - componentColors[2])  
                           alpha:componentColors[3]];  
      
}  

19 測試方法：
1.BIT_ViewController中viewDidLoad中注釋掉[BI_RootViewSDK create:textField_];
2.編譯出BaiduInputMethod.dylib
3.dsymutil BaiduInputMethod.dylib產生BaiduInputMethod.dylib.dSYM檔案夾
4.XCode->Product->Profile->Time Profile
5.啟動Instruments後，如果找不到符號，請Stop掉Instruments，然後File->Re-Symbolicate Document,再次啟動就可以了

20 一個訊息被多次發送，如何提高速度
當一個訊息要被發送給某個對象很多次的時候，可以直接使用methodForSelector:來進行最佳化，比如下述代碼：
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//////////////////////////////////////////////////////////////  
void (*setter)(id, SEL, BOOL);  
int i;  
  
setter = (void (*)(id, SEL, BOOL))[target  
     methodForSelector:@selector(setFilled:)];  
for ( i = 0; i < 1000, i++ )   
     setter(targetList[i], @selector(setFilled:), YES);  
//////////////////////////////////////////////////////////////  

其中，methodForSelector:是由Cocoa Runtime System提供的，而不是Objective-C本身的語言特性。這裡需要注意轉換過程中函數類型的正確性，包括傳回值和參數，而且這裡的前兩個參數需要顯示聲明為id和SEL。