iOS 之开发中的几个小技巧

1、Xcode调试技巧—在系统抛出异常处设置断点

有时候我们的程序不知道跑到哪个地方就 crash 了，而 crash 又很难重现。

保守的做法是在系统抛出异常之前设置断点，具体来说是在 objc_exception_throw处设置断点。

设置步骤为：首先在 XCode 按 CMD + 6，进入断点管理窗口；

然后点击右下方的 +，增加新的 Symbolic Breakpoint。

在 Symbol 一栏输入：objc_exception_throw，然后点击 done，完成。

这样在 Debug 模式下，如果程序即将抛出异常，就能在抛出异常处中断了。

比如在前面的代码中，我让 [firstObjctcrashTest]; 抛出异常。在 objc_exception_throw 处设置断点之后，程序就能在该代码处中断了，我们从而知道代码在什么地方出问题了。

2、计算UIlabel 随字体多行后的高度

+ (CGFloat)calcTextHeight:(int)textWidth text:(NSString *)text font:(int)fontSize {

CGRect bounds, result;

bounds = CGRectMake(0, 0, textWidth, 300);

UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];

label.font = [UIFont systemFontOfSize:fontSize];

label.text = text;

result = [label textRectForBounds:bounds limitedToNumberOfLines:20];

return result.size.height;

}

或者CGSize requiredSize = [introduceLabel.text sizeWithFont:[UIFont systemFontOfSize:14] constrainedToSize:CGSizeMake(296.0f, FLT_MAX) lineBreakMode:UILineBreakModeTailTruncation];

3、计算当前label随字体增加的长度（单行）

CGSize boundingSize = CGSizeMake(320.0f, CGFLOAT_MAX);

CGSize requiredSize = [status.user.username sizeWithFont:[UIFont boldSystemFontOfSize:13] constrainedToSize:boundingSize lineBreakMode:UILineBreakModeWordWrap];

CGFloat requiredWidth = requiredSize.width;

4、view控件加边框

profileImageButton = [UIButton buttonWithType:UIButtonTypeCustom];

[profileImageButton.layer setMasksToBounds:YES];

[profileImageButton.layer setCornerRadius:4.0]; //设置矩形四个圆角半径

[profileImageButton.layer setBorderWidth:1.0]; //边框宽度

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

CGColorRef colorref = CGColorCreate(colorSpace,(CGFloat[]){225.0/255.0, 225.0/255.0, 225.0/255.0, 1.0 });

[profileImageButton.layer setBorderColor:colorref];//边框颜色

单独设置圆角

[iconImage.layer setCornerRadius:4.0];

[iconImage setClipsToBounds:YES];

5、时区返回格式为数字(-12—+12)

-(NSString *)getTimeZone{

NSString *zone = [[NSTimeZone systemTimeZone] description];//Europe/Berlin// America/New_York// Asia/Harbin

//这三个可以用来测试exp:NSString *zone = [[NSTimeZone timeZoneWithName:@"America/New_York"] description];

NSString *time = [[zone componentsSeparatedByString:@"offset "] objectAtIndex:1];

int inv = [time intValue];

int result = inv / (60 * 60);

if (result>0) {

return [NSString stringWithFormat:@"+%d", result];

}

return [NSString stringWithFormat:@"%d", result];

}

6、判定输入框不为空格以及空

NSString *_textField=[textField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

if ([_textField length] == 0) {

UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"" message:@"评论内容不能为空！" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil];

[alertView show];

return NO;

}

7、根据当前键盘的高度来设置UITextField的位置

- (void)textFieldDidBeginEditing:(UITextField *)textField

{

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardDidShowNotification object:nil];

}

- (void)keyboardWillShow:(id)sender {

CGRect keyboardFrame;

[[[((NSNotification *)sender) userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardFrame];

CGFloat keyboardHeight = CGRectGetHeight(keyboardFrame);

[self.textImageView setFrame:CGRectMake(0, 416-keyboardHeight, 320, 45)];

}

8、设置label ,imageview,等点击时事件

UITapGestureRecognizer *imageTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapImage:)];

// [imageView setUserInteractionEnabled:YES]; 如果不能点击，设置可编辑

[imageView addGestureRecognizer:imageTap];

9、判断剩余字数（字母数字符号两个算一个汉字）

-(int)charNumber:(NSString *)strTemp

{

int strLength =1;

char *p =(char *) [strTemp cStringUsingEncoding:NSUnicodeStringEncoding];

for (int i=0; i<[strTemp lengthOfBytesUsingEncoding:NSUnicodeStringEncoding]; i++)

{

if (*p) {

p++;

strLength++;

}

else{

p++;

}

}

return strLength/2;

}

10、UIWebView加载gif图片 ——这样可以解决gif图片不能下载到本地加载，使用SDWebImage down也出现界面不流畅，卡的问题

UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, [homeTableCell getImageWidth:funnyPic], [homeTableCell getImageHeight:funnyPic])];

webView.backgroundColor = [UIColor clearColor];

// webView.scalesPageToFit = NO; 这一句我一直没搞清楚，有时对，有时不对的，注释了吧

//禁止webView的滑动 这样写主要是因为5.0以前的系统不能直接获取到webView.scrollView

[(UIScrollView *)[[webView subviews] objectAtIndex:0] setBounces:NO];

// 不让有白色的边，这个margin是必须的

NSString *html = [NSString stringWithFormat:@"<html><body style=\"margin: 0px;\"><img src=\"%@\"></body></html> ",funnyPic.imageUrl];

[webView loadHTMLString:html baseURL:nil];

[imageView addSubview:webView];

11、插入加载更多 tableview reloadData闪的问题

if (requestArray && [requestArray count] > 0) {

int cellCount = [requestArray count];//获取一共有几行

NSMutableArray *indexArray = [[NSMutableArray alloc]initWithCapacity:10];

int numCountNow = [self.tableView numberOfRowsInSection:0];

for (; cellCount > 0; cellCount--) {

NSIndexPath *path = [NSIndexPath indexPathForRow:numCountNow + cellCount - 1 inSection:0];

[indexArray addObject:path];

}

[self.tableView insertRowsAtIndexPaths:indexArray withRowAnimation:UITableViewRowAnimationNone];

}

12、Image 加载16进制的 图片（编译成freamwork的时候不能直接加载png图片，要转化）

首先，使用UltraEdit把图片转化为16进制

static const char _playerPause_icon [] = {

0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0x00, 0x00, 0x0D, 0x49, 0x48, 0x44, 0x52,

0x00, 0x00, 0x00, 0x11, 0x00, 0x00, 0x00, 0x1B, 0x08, 0x06, 0x00, 0x00, 0x00, 0x9A, 0xF6, 0x64,

0x9C, 0x00, 0x00, 0x00, 0x39, 0x49, 0x44, 0x41, 0x54, 0x38, 0x8D, 0x63, 0x64, 0x60, 0x60, 0x38,

0xC3, 0x80, 0x1D, 0x98, 0x60, 0x11, 0xC3, 0xAA, 0x96, 0xF1, 0xFF, 0xFF, 0xFF, 0xFF, 0xB1, 0x4A,

0x30, 0x32, 0x32, 0xA2, 0x8B, 0xE1, 0x52, 0xCB, 0x84, 0xC3, 0x15, 0x24, 0x81, 0x51, 0x43, 0x46,

0x0D, 0x19, 0x35, 0x64, 0xD4, 0x90, 0x51, 0x43, 0x46, 0x0D, 0xA1, 0xA7, 0x21, 0x00, 0xDD, 0x84,

0x09, 0xFD, 0x6B, 0x3C, 0x1F, 0xCB, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4E, 0x44, 0xAE, 0x42,

0x60, 0x82

};

然后加载

[playButton setImage:[UIImage imageWithData:[NSData dataWithBytes:_playerPause_icon length:sizeof(_playerPause_icon)/sizeof(char)]] forState:UIControlStateNormal];

13、倒计时（剩余时间）

- (void)timerFireMethod:(NSTimer*)theTimer{

id obj = [theTimer userInfo];

NSDateFormatter *f1 = [[NSDateFormatter alloc] init];

[f1 setDateFormat:@"yyyy-MM-dd HH:mm:ss.S"];

NSDate *theDay = [f1 dateFromString:(NSString*)obj];

[f1 release];

NSCalendar *cal = [NSCalendar currentCalendar];//定义一个NSCalendar对象

NSDate *today = [NSDate date];//得到当前时间

//用来得到具体的时差

unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

NSDateComponents *d = [cal components:unitFlags fromDate:today toDate:theDay options:0];

NSString *countdown = [NSString stringWithFormat:@"%d日%d时%d分%d秒", [d month],[d day], [d hour], [d minute], [d second]];

self.timeLabel.text = countdown;

return ;

}

14、九宫格或者其他类型的坐标设置

frame.size.width = 60;//设置按钮坐标及大小

frame.size.height = 60;

frame.origin.x = (i%3)*(60 + 32)+40;

frame.origin.y
= floor(i/3)*(60 + 24)+60;