iphone develop tips

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一些iphone的小细节，小技巧
1.时间戳
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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 结果：
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hex=4fd7fd8a,dec=1339555210,milSec=1339555210.191
2.UIView圆角实现
包含QuartzCore.framework ，然后包含头文件#import <QuartzCore/QuartzCore.h>
使用以下的两行代码既可。
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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];
[cpp] view plaincopy

设置边框颜色，
UIView* view = [[UIView alloc] initWithFrame:CGRectZero];
view.layer.borderWidth = 1.0;
view.layer.borderColor = [UIColor redColor].CGColor;

3.用图片平铺做背景
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UIView* tmpView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
tmpView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"bg.png"]];

4.用图片拉伸做背景
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UIImageView* tmpView2 = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
tmpView2.image = [UIImage imageNamed:@"bg.png"];

UIImageView 的ContentMode默认是 UIViewContentModeScaleToFill，即拉伸，可以选择居中，左对齐，右对齐来不拉伸显示。
5.使用UIView的transform属性做旋转等动画，在使用完成后需要重新设置transform为默认 CGAffineTransformIdentity，否则下次setframe等操作时，现实错误。
6.使用UILabel时，设置setFrame需要保证CGrect 的值未整数，不能为浮点，否则系统自动做抗锯齿，现实模糊。图片存在同样问题。
7.播放gif动画
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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.隐藏tabbar之后，底部出现一个白条，去除方法
http://stackoverflow.com/questions/1982172/iphone-is-it-possible-to-hide-the-tabbar
隐藏：
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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;
显示：
[cpp] view plaincopy

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

9.在导航栏中间加入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 表示导航栏中间的view，另外，如果左右两边分别也有UIBarButtonItem，通过 self.navigationItem.leftBarButtonItem 和 self.navigationItem.rightBarButtonItem 来引用。
10，根据地址查看对应符号和地址
dwarfdump --lookup 0x0000641c -arch armv6 EmergencyNumbers.app.dSYM

11.动态设置UITextField是否安全输入
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NSString* pass = passWordTextField_.text;
passWordTextField_.enabled = NO;
passWordTextField_.secureTextEntry = !isShowPassWord_;
passWordTextField_.enabled = YES;
[passWordTextField_ becomeFirstResponder];
passWordTextField_.text = pass;

11,点击事件穿透父视图，让子图响应事件
参考：http://cocoaheads.tumblr.com/post/2130871776/ignore-touches-to-uiview-subclass-but-not-to-its
要将父视图的userInteractionEnabled 设为 YES
[cpp] view plaincopy

-(id)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
id hitView = [super hitTest:point withEvent:event];
if (hitView == self) return nil;
else return hitView;
}

12，让视图只响应某个区域的点击事件，利用11中提到方法
以下代码实现让view只响应CGRectMake(0, 0, 160, 40) 区域的事件
[cpp] view plaincopy

- (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，屏幕截图
[cpp] view plaincopy

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();
//然后将该图片保存到图片图
UIImageWriteToSavedPhotosAlbum(image,self,nil,nil);

14，由颜色生成图片
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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 点击效果

[cpp] view plaincopy

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. 移动光标到末尾
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UITextView * m_textInput;
//设置光标到输入文字的末尾
NSUInteger length = m_textInput.text.length;
m_textInput.selectedRange = NSMakeRange(length,0);

17.Xcode添加doxygen注释
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 测试方法：
1.BIT_ViewController中viewDidLoad中注释掉[BI_RootViewSDK create:textField_];
2.编译出BaiduInputMethod.dylib
3.dsymutil BaiduInputMethod.dylib产生BaiduInputMethod.dylib.dSYM文件夹
4.XCode->Product->Profile->Time Profile
5.启动Instruments后，如果找不到符号，请Stop掉Instruments，然后File->Re-Symbolicate Document,再次启动就可以了

20 一个消息被多次发送，如何提高速度
当一个消息要被发送给某个对象很多次的时候，可以直接使用methodForSelector:来进行优化，比如下述代码：
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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本身的语言特性。这里需要注意转换过程中函数类型的正确性，包括返回值和参数，而且这里的前两个参数需要显示声明为id和SEL。


	
					
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