25條iOS開發中類型的轉換和常用的知識點-總結

在寫代碼的時候很容易被一些那些我們看似簡單的問題難住，也嚴重影響了我們工作的進度，所以今天把一些在iOS中常用 關於類型的轉換和常用的用法總結下。

字符的表示含義：

%c 一個單一的字符

%d 一個十進制整數
%i 一個整數 //原來i%是這個區別啊
%e, %f, %g 一個浮點數
%o 一個八進制數
%s 一個字符串
%x 一個十六進制數
%p 一個指針  //也挺特別的
%n 一個等於讀取字符數量的整數 //特別的東東
%u 一個無符號整數
%[] 一個字符集  //沒見過
%% 一個精度符號


//一、NSString
/*—————-創建字符串的方法—————-*/


1、創建常量字符串。
NSString *astring = @”This is a String!”;


2、創建空字符串，給予賦值。
NSString *astring = [[NSString alloc] init];
astring = @”This is a String!”;
NSLog(@”astring:%@”,astring);  //NSLog要這麼用？反正當直接使用NSLog(astring)會有警告
[astring release];


3、在以上方法中，提升速度:initWithString方法
NSString *astring = [[NSString alloc] initWithString:@”This is a String!”];
NSLog(@”astring:%@”,astring);
[astring release];


 


4、用標準c創建字符串:initWithCString方法
char *Cstring = “This is a String!”;
NSString *astring = [[NSString alloc] initWithCString:Cstring];
NSLog(@”astring:%@”,astring);
[astring release];


5、創建格式化字符串:佔位符（由一個%加一個字符組成）
int i = 1;
int j = 2;
NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];
NSLog(@”astring:%@”,astring);
[astring release];


6、創建臨時字符串
NSString *astring;
astring = [NSString stringWithCString:"This is a temporary string"];
NSLog(@”astring:%@”,astring);


/*—————-從文件讀取字符串:initWithContentsOfFile方法 —————-*/
NSString *path = @”astring.text”;
NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
NSLog(@”astring:%@”,astring);
[astring release];


/*—————-寫字符串到文件:writeToFile方法 —————-*/
NSString *astring = [[NSString alloc] initWithString:@”This is a String!”];
NSLog(@”astring:%@”,astring);
NSString *path = @”astring.text”;
[astring writeToFile: path atomically: YES];
[astring release];


/*—————- 比較兩個字符串—————-*/
用C比較:strcmp函數
char string1[] = “string!”;
char string2[] = “string!”;
if(strcmp(string1, string2) = = 0)
{
NSLog(@”1″);
}


isEqualToString方法
NSString *astring01 = @”This is a String!”;
NSString *astring02 = @”This is a String!”;
BOOL result = [astring01 isEqualToString:astring02];
NSLog(@”result:%d”,result);


compare方法(comparer返回的三種值)
NSString *astring01 = @”This is a String!”;
NSString *astring02 = @”This is a String!”;
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
NSLog(@”result:%d”,result);
NSOrderedSame 判斷兩者內容是否相同


NSString *astring01 = @”This is a String!”;
NSString *astring02 = @”this is a String!”;
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
NSLog(@”result:%d”,result);
//NSOrderedAscending 判斷兩對象值的大小(按字母順序進行比較，astring02大於astring01爲真)


NSString *astring01 = @”this is a String!”;
NSString *astring02 = @”This is a String!”;
BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;
NSLog(@”result:%d”,result);
//NSOrderedDescending 判斷兩對象值的大小(按字母順序進行比較，astring02小於astring01爲真)


不考慮大 小寫比較字符串1
NSString *astring01 = @”this is a String!”;
NSString *astring02 = @”This is a String!”;
BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
NSLog(@”result:%d”,result);
//NSOrderedDescending判斷兩對象值的大小(按字母順序進行比較，astring02小於astring01爲 真)


不考慮大小寫比較字符串2
NSString *astring01 = @”this is a String!”;
NSString *astring02 = @”This is a String!”;
BOOL result = [astring01 compare:astring02
options:NSCaseInsensitiveSearch | NSNumericSearch] = = NSOrderedSame;
NSLog(@”result:%d”,result);


//NSCaseInsensitiveSearch:不區分大小寫比較 NSLiteralSearch:進行完全比較，區分大小寫 NSNumericSearch:比較字符串的字符個數，而不是字符值。


/*—————-改變字符串的大小寫—————-*/
NSString *string1 = @”A String”;
NSString *string2 = @”String”;
NSLog(@”string1:%@”,[string1 uppercaseString]);//大寫
NSLog(@”string2:%@”,[string2 lowercaseString]);//小寫
NSLog(@”string2:%@”,[string2 capitalizedString]);//首字母大小


/*—————-在串中搜索子串 —————-*/
NSString *string1 = @”This is a string”;
NSString *string2 = @”string”;
NSRange range = [string1 rangeOfString:string2];
int location = range.location;
int leight = range.length;
NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i",location,leight]];
NSLog(@”astring:%@”,astring);
[astring release];


 


 


/*—————-抽取子串 —————-*/
-substringToIndex: 從字符串的開頭一直截取到指定的位置，但不包括該位置的字符
NSString *string1 = @”This is a string”;
NSString *string2 = [string1 substringToIndex:3];
NSLog(@”string2:%@”,string2);


-substringFromIndex: 以指定位置開始（包括指定位置的字符），幷包括之後的全部字符
NSString *string1 = @”This is a string”;
NSString *string2 = [string1 substringFromIndex:3];
NSLog(@”string2:%@”,string2);


-substringWithRange: //按照所給出的位置，長度，任意地從字符串中截取子串
NSString *string1 = @”This is a string”;
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
NSLog(@”string2:%@”,string2);


const char *fieldValue = [value cStringUsingEncoding:NSUTF8StringEncoding];
const char *fieldValue = [value UTF8String];


NSString 轉 NSData
NSString* str= @”kilonet”;
NSData* data=[str dataUsingEncoding:NSUTF8StringEncoding];


Date format用法：
-(NSString *) getDay:(NSDate *) d
{
NSString *s ;
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:@"YYYY/MM/dd hh:mm:ss"];
s = [format stringFromDate:d];
[format release];
return s;
}


各地時區獲取：


代碼
NSDate *nowDate = [NSDate new]; //竟然是這個樣子，幹嘛，四不像。你以爲你是c++啊
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy/MM/dd HH:mm:ss"];
// 根據時區名字獲取當前時間，如果該時區不存在，默認獲取系統當前時區的時間
// NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:@"Europe/Andorra"];
// [formatter setTimeZone:timeZone];
//獲取所有的時區名字
NSArray *array = [NSTimeZone knownTimeZoneNames];
// NSLog(@”array:%@”,array);
//for循環
// for(int i=0;i<[array count];i++)
// {
// NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:[array objectAtIndex:i]];
// [formatter setTimeZone:timeZone];
// NSString *locationTime = [formatter stringFromDate:nowDate];
// NSLog(@"時區名字:%@ : 時區當前時間: %@",[array objectAtIndex:i],locationTime);
// //NSLog(@"timezone name is:%@",[array objectAtIndex:i]);
// }
//快速枚舉法
for(NSString *timeZoneName in array){
[formatter setTimeZone:[NSTimeZone timeZoneWithName:timeZoneName]];
NSLog(@"%@,%@",timeZoneName,[formatter stringFromDate:nowDate]);
}


[formatter release];
[nowDate release];


NSCalendar用法：


-(NSString *) getWeek:(NSDate *) d {
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
unsigned units = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekdayCalendarUnit;
NSDateComponents *components = [calendar components:units fromDate:d];
[calendar release];


switch ([components weekday]) {
case 2:
return @"Monday";
break;
case 3:
return @"Tuesday";
break;
case 4:
return @"Wednesday";
break;
case 5:
return @"Thursday";
break;
case 6:
return @"Friday";
break;
case 7:
return @"Saturday";
break;
case 1:
return @"Sunday";
break;
default:
return @"No Week";
break;
}


// 用components，我們可以讀取其他更多的數據。


}


4. 用Get方式讀取網絡數據：


將網絡數讀取爲字符串
- (NSString *) getDataByURL:(NSString *) url {
return [[NSString alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]] encoding:NSUTF8StringEncoding];
}


//讀取網絡圖片
- (UIImage *) getImageByURL:(NSString *) url {
return [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]]];
}


多線程（這種方式，只管建立線程，不管回收線程，爲什麼大家都只會這種方式）
[NSThread detachNewThreadSelector:@selector(scheduleTask) toTarget:self withObject:nil];


-(void) scheduleTask {
//create a pool
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];


//release the pool;
[pool release];
}




//如果有參數，則這麼使用：//注意這裏有個冒號
[NSThread detachNewThreadSelector:@selector(scheduleTask:) toTarget:self withObject:[NSDate date]];


-(void) scheduleTask:(NSDate *) mdate {
//create a pool  這裏都重新建立一個內存池！！！
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];


//release the pool;
[pool release];
}


//注意selector裏有冒號。
//在線程裏運行主線程裏的方法


[self performSelectorOnMainThread:@selector(moveToMain) withObject:nil waitUntilDone:FALSE];


6. 定時器NSTimer用法:


代碼
// 一個可以自動關閉的Alert窗口


UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil
message:[@"一個可以自動關閉的Alert窗口"
delegate:nil
cancelButtonTitle:nil //NSLocalizedString(@"OK", @"OK") //取消任何按鈕
otherButtonTitles:nil];
//[alert setBounds:CGRectMake(alert.bounds.origin.x, alert.bounds.origin.y, alert.bounds.size.width, alert.bounds.size.height+30.0)];
[alert show];


UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];


// Adjust the indicator so it is up a few pixels from the bottom of the alert
indicator.center = CGPointMake(alert.bounds.size.width/2, alert.bounds.size.height-40.0);
[indicator startAnimating];
[alert insertSubview:indicator atIndex:0];
[indicator release];


[NSTimer scheduledTimerWithTimeInterval:3.0f
target:self
selector:@selector(dismissAlert:)
userInfo:[NSDictionary dictionaryWithObjectsAndKeys:alert, @"alert", @"testing ", @"key" ,nil] //如果不用傳遞參數，那麼可以將此項設置爲nil.
repeats:NO];


NSLog(@"release alert");
[alert release];


-(void) dismissAlert:(NSTimer *)timer{


NSLog(@"release timer");
NSLog([[timer userInfo] objectForKey:@"key"]);


UIAlertView *alert = [[timer userInfo] objectForKey:@"alert"];
[alert dismissWithClickedButtonIndex:0 animated:YES];


}


定時器停止使用：


[timer invalidate];
timer = nil;


7. 用戶缺省值NSUserDefaults讀取：


//得到用戶缺省值
NSUserDefaults *defs = [NSUserDefaults standardUserDefaults];


//在缺省值中找到AppleLanguages, 返回值是一個數組
NSArray* languages = [defs objectForKey:@"AppleLanguages"];
NSLog(@"all language語言 is %@", languages);


//在得到的數組中的第一個項就是用戶的首選語言了
NSLog(@"首選語言 is %@",[languages objectAtIndex:0]);


//get the language & country code
NSLocale *currentLocale = [NSLocale currentLocale];


NSLog(@"Language Code is %@", [currentLocale objectForKey:NSLocaleLanguageCode]);
NSLog(@"Country Code is %@", [currentLocale objectForKey:NSLocaleCountryCode


8. View之間切換的動態效果設置：//這麼簡單。。這個類很強大啊


SettingsController *settings = [[SettingsController alloc]initWithNibName:@"SettingsView" bundle:nil];
settings.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; //水平翻轉
[self presentModalViewController:settings animated:YES];
[settings release];


9.NSScrollView 滑動用法：


-(void) scrollViewDidScroll:(UIScrollView *)scrollView{
NSLog(@"正在滑動中...");
}


//用戶直接滑動NSScrollView，可以看到滑動條
-(void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView {


}


// 通過其他控件觸發NSScrollView滑動，看不到滑動條
- (void) scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {


}


11.鍵盤處理系列


//set the UIKeyboard to switch to a different text field when you press return


//switch textField to the name of your textfield
[textField becomeFirstResponder];


srandom(time(NULL)); //隨機數種子


id d = random(); // 隨機數


4. iPhone的系統目錄:


//得到Document目錄：
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];


//得到temp臨時目錄：
NSString *tempPath = NSTemporaryDirectory();


//得到目錄上的文件地址：
NSString *文件地址 = [目錄地址 stringByAppendingPathComponent:@"文件名.擴展名"];


5. 狀態欄顯示Indicator：


[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;


6.app Icon顯示數字：


- (void)applicationDidEnterBackground:(UIApplication *)application{
[[UIApplication sharedApplication] setApplicationIconBadgeNumber:5];
}


7.sqlite保存地址：


代碼
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *thePath = [paths objectAtIndex:0];
NSString *filePath = [thePath stringByAppendingPathComponent:@"kilonet1.sqlite"];


NSString *dbPath = [[[NSBundle mainBundle] resourcePath]
stringByAppendingPathComponent:@"kilonet2.sqlite"];


8.Application退出：exit(0);


9. AlertView，ActionSheet的cancelButton點擊事件：


代碼
-(void) actionSheet  UIActionSheet *) actionSheet didDismissWithButtonIndex:(NSInteger) buttonIndex {
NSLog(@"cancel actionSheet........");
//當用戶按下cancel按鈕
if( buttonIndex == [actionSheet cancelButtonIndex]) {
exit(0);
}
// //當用戶按下destructive按鈕
// if( buttonIndex == [actionSheet destructiveButtonIndex]) {
// // DoSomething here.
// }
}


- (void)alertView:(UIAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex {
NSLog(@"cancel alertView........");
if (buttonIndex == [alertView cancelButtonIndex]) {
exit(0);
}
}


10.給Window設置全局的背景圖片：
window.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"coolblack.png"]];


11. UITextField文本框顯示及對鍵盤的控制:


代碼
#pragma mark -
#pragma mark UITextFieldDelegate
//控制鍵盤跳轉
- (BOOL)textFieldShouldReturn:(UITextField *)textField {


if (textField == _txtAccount) {
if ([_txtAccount.text length]==0) {
return NO;
}
[_txtPassword becomeFirstResponder];
} else if (textField == _txtPassword) {
[_txtPassword resignFirstResponder];
}


return YES;
}


//輸入框背景更換
-(BOOL) textFieldShouldBeginEditing:(UITextField *)textField{


[textField setBackground:[UIImage imageNamed:@"ctext_field_02.png"]];


return YES;
}


-(void) textFieldDidEndEditing:(UITextField *)textField{
[textField setBackground:[UIImage imageNamed:@"ctext_field_01.png"]];
}


12.UITextField文本框前面空白寬度設置以及後面組合按鈕設置：


代碼
//給文本輸入框後面加入空白
_txtAccount.rightView = _btnDropDown;
_txtAccount.rightViewMode = UITextFieldViewModeAlways;


//給文本輸入框前面加入空白
CGRect frame = [_txtAccount frame];
frame.size.width = 5;
UIView *leftview = [[UIView alloc] initWithFrame:frame];
_txtAccount.leftViewMode = UITextFieldViewModeAlways;
_txtAccount.leftView = leftview;


13. UIScrollView 設置滑動不超出本身範圍：


[fcScrollView setBounces:NO];


14. 遍歷View裏面所有的Subview：


代碼
NSLog(@"subviews count=%d",[self.view.subviews count]);
if ([self.view.subviews count] > 0) {
for (UIView *curView in self.view.subviews) {
NSLog(@”view.subviews=%@”, [NSString stringWithUTF8String:object_getClassName(curView)]);
}
}


14. 在drawRect裏畫文字：


UIFont * f = [UIFont systemFontOfSize:20];


[[UIColor darkGrayColor] set];


NSString * text = @”hi \nKiloNet”;


[text drawAtPoint:CGPointMake(center.x,center.y) withFont:f];


15. NSArray查找是否存在對象時用indexOfObject,如果不存在則返回爲NSNotFound.


16. NString與NSArray之間相互轉換：


array = [string componentsSeparatedByString:@","];
string = [[array valueForKey:@"description"] componentsJoinedByString:@”,”];


17. TabController隨意切換tab bar：


[self.tabBarController setSelectedIndex:tabIndex];


或者 self.tabBarController.selectedIndex = tabIndex;


或者實現下面的delegate來撲捉tab bar的事件：


代碼-(BOOL) tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController { if ([viewController.tabBarItem.title isEqualToString: NSLocalizedString(@"Logout",nil)]) { [self showLogout]; return NO; } return YES;}


18. 自定義View之間切換動畫：
代碼
- (void) pushController: (UIViewController*) controller
withTransition: (UIViewAnimationTransition) transition
{
[UIView beginAnimations:nil context:NULL];
[self pushViewController:controller animated:NO];
[UIView setAnimationDuration:.5];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationTransition:transition forView:self.view cache:YES];
[UIView commitAnimations];
}


CATransition *transition = [CATransition animation];
transition.duration = kAnimationDuration;
transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
transition.type = kCATransitionPush;
transition.subtype = kCATransitionFromTop;
transitioning = YES;
transition.delegate = self;
[self.navigationController.view.layer addAnimation:transition forKey:nil];


self.navigationController.navigationBarHidden = NO;
[self.navigationController pushViewController:tableViewController animated:YES];


20.計算字符串長度：


CGFloat w = [title sizeWithFont:[UIFont fontWithName:@"Arial" size:18]].width;


23.在使用UISearchBar時，將背景色設定爲clearColor，或者將translucent設爲YES，都不能使背景透明，經過一番研究，發現了一種超級簡單和實用的方法：


1
[[searchbar.subviews objectAtIndex:0]removeFromSuperview];


背景完全消除了，只剩下搜索框本身了。


24. 圖像與緩存 :


UIImageView *wallpaper = [[UIImageView alloc] initWithImage:


[UIImage imageNamed:@"icon.png"]]; // 會緩存圖片


UIImageView *wallpaper = [[UIImageView alloc] initWithImage:


[UIImage imageWithContentsOfFile:@"icon.png"]]; // 不會緩存圖片


25. iphone-常用的對視圖圖層(layer)的操作


對圖層的操作：


(1.給圖層添加背景圖片：//這裏都是layer的，要研究下layer
myView.layer.contents = (id)[UIImage imageNamed:@"view_BG.png"].CGImage;


(2.將圖層的邊框設置爲圓腳
myWebView.layer.cornerRadius = 8;
myWebView.layer.masksToBounds = YES;


(3.給圖層添加一個有色邊框
myWebView.layer.borderWidth = 5;
myWebView.layer.borderColor = [[UIColor colorWithRed:0.52 green:0.09 blue:0.07 alpha:1] CGColor];