★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._%+-]+@[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];
