知识点回顾-27个iOS开发中的小技巧

★27个iOS开发中的小技巧

1、不想让TableView显示无用的Cell分割线怎么办？

self.tableView.tableFooterView = [[UIView alloc] init];
2、自定义了leftBarbuttonItem左滑返回手势失效了怎么办？

self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]
                                         initWithImage:img
                                         style:UIBarButtonItemStylePlain
                                         target:self
                                         action:@selector(onBack:)];
self.navigationController.interactivePopGestureRecognizer.delegate = (id<uigesturerecognizerdelegate>)self;</uigesturerecognizerdelegate>
3、在ioS7中，如何检测系统自带ViewController手势返回结束？

-(void)navigationController:(UINavigationController*)navigationControllerwillShowViewController:(UIViewController*)viewControlleranimated:(BOOL)animated
{
id<UIViewControllerTransitionCoordinator>tc=navigationController.topViewController.transitionCoordinator;
[tcnotifyWhenInteractionEndsUsingBlock:^(id<UIViewControllerTransitionCoordinatorContext>context){
NSLog(@"7:%i",[contextisCancelled]);
}];
}
4、ScrollView莫名其妙不能在viewController划到顶怎么办？

self.automaticallyAdjustsScrollViewInsets = NO;
5、在不新建一个Cell的情况下，怎么调整separaLine的位置？

_myTableView.separatorInset = UIEdgeInsetsMake(0, 100, 0, 0);
6、怎么点击self.view就让键盘收起，需要添加一个tapGestures吗？

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
   [self.view endEditing:YES];
}
7、怎么像safari一样滑动的时候隐藏navigationbar？

navigationController.hidesBarsOnSwipe = Yes
8、导航条返回键带的title太讨厌了，怎么让它消失？

[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60)
                                                     forBarMetrics:UIBarMetricsDefault];
9、CollectionView 怎么实现tableview那种悬停的header？

CSStickyHeaderFlowLayou
10、能不能只用一个pan手势来代替UISwipegesture的各个方向？

- (void)pan:(UIPanGestureRecognizer *)sender
{
typedef NS_ENUM(NSUInteger, UIPanGestureRecognizerDirection) {
    UIPanGestureRecognizerDirectionUndefined,
    UIPanGestureRecognizerDirectionUp,
    UIPanGestureRecognizerDirectionDown,
    UIPanGestureRecognizerDirectionLeft,
    UIPanGestureRecognizerDirectionRight
};
static UIPanGestureRecognizerDirection direction = UIPanGestureRecognizerDirectionUndefined;
switch (sender.state) {
    case UIGestureRecognizerStateBegan: {
        if (direction == UIPanGestureRecognizerDirectionUndefined) {
            CGPoint velocity = [sender velocityInView:recognizer.view];
            BOOL isVerticalGesture = fabs(velocity.y) > fabs(velocity.x);
            if (isVerticalGesture) {
                if (velocity.y > 0) {
                    direction = UIPanGestureRecognizerDirectionDown;
                } else {
                    direction = UIPanGestureRecognizerDirectionUp;
                }
            }
            else {
                if (velocity.x > 0) {
                    direction = UIPanGestureRecognizerDirectionRight;
                } else {
                    direction = UIPanGestureRecognizerDirectionLeft;
                }
            }
        }
        break;
    }
    case UIGestureRecognizerStateChanged: {
        switch (direction) {
            case UIPanGestureRecognizerDirectionUp: {
                [self handleUpwardsGesture:sender];
                break;
            }
            case UIPanGestureRecognizerDirectionDown: {
                [self handleDownwardsGesture:sender];
                break;
            }
            case UIPanGestureRecognizerDirectionLeft: {
                [self handleLeftGesture:sender];
                break;
            }
            case UIPanGestureRecognizerDirectionRight: {
                [self handleRightGesture:sender];
                break;
            }
            default: {
                break;
            }
        }
        break;
    }
    case UIGestureRecognizerStateEnded: {
        direction = UIPanGestureRecognizerDirectionUndefined;
        break;
    }
    default:
        break;
}
}
11、怎么把tableview里cell的小对勾的颜色改成别的颜色？

_mTableView.tintColor = [UIColor redColor];
12、本来我的statusbar是lightcontent的，结果用UIImagePickerController会导致我的statusbar的样式变成黑色，怎么办？

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
}
13、怎么把我的navigationbar弄成透明的而不是带模糊的效果？

[self.navigationBar setBackgroundImage:[UIImage new]
                         forBarMetrics:UIBarMetricsDefault];
self.navigationBar.shadowImage = [UIImage new];
self.navigationBar.translucent = YES;
14、怎么改变uitextfield placeholder的颜色和位置？

继承uitextfield，重写这个方法：

- (void) drawPlaceholderInRect:(CGRect)rect {
    [[UIColor blueColor] setFill];
    [self.placeholder drawInRect:rect withFont:self.font lineBreakMode:UILineBreakModeTailTruncation alignment:self.textAlignment];
}
15、添加需要的不同语言字符串

简体中文Localizable.strings文件：

"REMIND"="提示";
"OK"="确定";
"CANCEL"="取消";
"NetworkConnectError"="网络连接失败";

英文版Localizable.strings文件：

"REMIND"="Remind";
"OK"="OK";
"CANCEL"="Cancel";
"NetworkConnectError"="Cannot Connect Network";

注意：不要遗漏结尾的分号“;”
16、使用国际化文件

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"REMIND", nil) message:NSLocalizedString(@"NetworkConnectError", nil) delegate:self cancelButtonTitle:NSLocalizedString(@"CANCEL", nil) otherButtonTitles:NSLocalizedString(@"OK", nil), nil];
[alert show];
17、遍历实践Tips

倒序遍历

NSArray和NSOrderedSet都支持使用reverseObjectEnumerator倒序遍历，如：

NSArray *strings = @[@"1", @"2", @"3"];
for (NSString *string in [strings reverseObjectEnumerator]) {
    NSLog(@"%@", string);
}

这个方法只在循环第一次被调用，所以不必担心循环每次计算的问题。

同时，使用enumerateObjectsWithOptions:NSEnumerationReverse也可以实现倒序遍历：

[array enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(Sark *sark, NSUInteger idx, BOOL *stop) {
    [sark doSomething];
}];

使用block同时遍历字典key，value

block版本的字典遍历可以同时取key和value（forin只能取key再手动取value），如：

NSDictionary *dict = @{@"a": @"1", @"b": @"2"};
[dict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
    NSLog(@"key: %@, value: %@", key, obj);
}];

对于耗时且顺序无关的遍历，使用并发版本：

[array enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(Sark *sark, NSUInteger idx, BOOL *stop) {
    [sark doSomethingSlow];
}];
18、如果在程序中想对某张图片进行处理的话（如得到某张图片的一部分）怎么做？

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];
19、如何判断邮箱输入的是否正确？

- (BOOL) validateEmail: (NSString *) candidate {

NSString *emailRegex = @"[A-Z0-9a-z._%+-][email protected][A-Za-z0-9.-]+\.[A-Za-z]{2,4}";

NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];

return [emailTest evaluateWithObject:candidate];

}
20、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(viewIm
21、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];
22、捕获iphone通话事件

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

center.callEventHandler = ^(CTCall *call)

{

NSLog(@"call:%@", call.callState);
23、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);

}
24、iPad隐藏键盘的同时触发方法

[[NSNotificationCenter defaultCenter] addObserver:self

selector:@selector(keyboardWillHide:)

name:UIKeyboardWillHideNotification

  object:nil];

- (IBAction)keyboardWillHide:(NSNotification *)note
25、设置时区

NSTimeZone *defaultTimeZone = [NSTimeZone defaultTimeZone];

NSTimeZone *tzGMT = [NSTimeZone timeZoneWithName:@"GMT"];

[NSTimeZone setDefaultTimeZone:tzGMT];
26、在程序中实现电话的拨打

//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];

//点击拨号按钮直接拨号

[btnPhone addTarget:self action:@selector(callAction:event:)forControlEvents:UIControlEventTouchUpInside];

[cell.contentView addSubview:btnPhone];  //cell是一个UITableViewCell

//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

}
27、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];

[UIView beginAnimations:nil context:nil];

[UIView setAnimationDuration:2];

frame.origin.x += 150;

[img setFrame:frame];

[UIView commitAnimations];
时间： 2024-10-19 13:49:51

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