开发小技巧2

1.TableView不显示没内容的Cell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)self;

3.ScrollView莫名其妙不能在viewController划到顶怎么办?

self.automaticallyAdjustsScrollViewInsets = NO;

4.怎么在不新建一个Cell的情况下调整separaLine的位置?

整体:
self.myTableView.separatorInset = UIEdgeInsetsMake(0, 100, 0, 0);
单个:
cell.separatorInset = UIEdgeInsetsMake(0, 100, 0, 0);

5.怎么点击self.view就让键盘收起,需要添加一个tapGestures么?

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
  [self.view endEditing:YES];
}

6.怎么像safari一样滑动的时候隐藏navigationbar?

navigationController.hidesBarsOnSwipe = Yes

7.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];

8.CollectionView 怎么实现tableview那种悬停的header?

CSStickyHeaderFlowLayou

9.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;
}
}

10.1 拉伸图片的时候怎么才能让图片不变形？

1.UIImage *image = [[UIImage imageNamed:@"xxx"] stretchableImageWithLeftCapWidth:10 topCapHeight:10];

2.

11.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];
}

12.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;

13.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];
}