IOS UI Basics 05

• Uiscrollview
  • Uiscrollview Steps to use
    • 1. Create Uiscrollview
    • 2. Add the content you want to show to the Uiscrollview
    • 3. Set the scroll range of the Uiscrollview (contentsize)
  • Note: If you want Uiscrollview to scroll, you must set a range that you can scroll
  • ScrollView can not scroll in several cases
    • 1. Contentsize not set
    • 2.scrollEnabled property = NO
    • 3.userInteractionEnabled property = NO
  • The difference between enabled and userinteractionenabled
    • Enabled: Represents a control that is not available
    • Userinteractionenabled: Represents a control that cannot interact with the user, that is, does not respond to user actions
  • Common Properties
    • Go to scroll bar
      • The scrollbar is also part of the ScrollView child control//scroll bar may be in front of the child control, or it may be behind the child control//Just because of this primitive, so it is not recommended in development to manipulate child controls in the way that subviews gets child controls

        self.scrollView.showsHorizontalScrollIndicator = NO;self.scrollView.showsVerticalScrollIndicator = NO;

    • Set the style of the scroll bar

      self.scrollView.indicatorStyle=UIScrollViewIndicatorStyleWhite;

    • The default Uiscrollview has a rebound effect as long as the contentsize is set to rebound effect

      self.scrollView.bounces = YES/NO;

    • Even if not set contentsize can also have rebound effect

      self.scrollView.alwaysBounceVertical = YES;self.scrollView.alwaysBounceHorizontal = YES;

    • Set Margin Contentinset

      self.scrollView.contentInset = UIEdgeInsetsMake(10, 20, 30, 40);

    • Set content bias shift (Contentoffset)
      • It's actually setting the ScrollView to where to scroll.
      • Tell ScrollView how much to move in the x direction and how much to move in the y direction
      • If X is positive: The picture moves to the left
      • If X is negative: The picture moves to the right
      • The same y is positive: the picture moves upwards
      • Y is negative: the picture moves down
      • Calculation formula: Always in the upper-left corner of the control – the upper-left corner of the content
    • Proxy method
      • As long as the agent of Uiscrollview, abide by the agent protocol, implement the method in the Protocol
      • The system automatically calls these proxy methods when Uiscrollview changes.
      • As soon as the Uiscrollview scrolls, the system will automatically call
        • -(void) Scrollviewdidscroll: (Uiscrollview *) ScrollView
      • As long as the user is ready to start dragging, it calls

        - -(void)scrollViewWillBeginDragging:(nonnull UIScrollView *)scrollView

      • User has finished dragging, on behalf of the user has let go of the system called the method does not mean that the Uiscrollview has stopped scrolling

        - -(void)scrollViewDidEndDragging:(nonnull UIScrollView *)scrollView willDecelerate:(BOOL)decelerate

      • The only way to do this is to represent that Uiscrollview has stopped scrolling.

        - -(void)scrollViewDidEndDecelerating:(nonnull UIScrollView *)scrollView

        + NOTE: If you want to do something after the Uiscrollview stops scrolling, there are two things
        • 1. No inertia: Only the method of stopping dragging is called, and the method of stopping deceleration is not called.
        • 2. Inertia situation: Both the method of stopping dragging is called, and the method of stopping deceleration is called.
        • So: To determine whether Uiscrollview stops scrolling, you need to rewrite two methods at a time

           + scrollViewDidEndDragging + scrollViewDidEndDecelerating

• Scaling
  • 1. Become an agent and tell Uiscrollview which child control to scale by proxy method
    • In this method, tell Uisrollview which control to scale

      UIView *)viewForZoomingInScrollView:(nonnull UIScrollView *)scrollView

  • 2. To scale, in addition to telling Uisrollview which control to scale, tell Uisrollview how small the minimum can be, how large the maximum can be self.sc.maximumzoomscale = 2.0; Maximum 2.0self.sc .minimumzoomscale = 0.5; min 0.5
    • 3. In the process of scaling calls and scrollviewdidscroll, as long as scaling a little bit will call

       -(void)
       Scrollviewdidzoom: (nonnull uiscrollview *) scrollView    

  • 1. Called when the zoom ends

       -(void)scrollViewDidEndZooming:(nonnull UIScrollView *)scrollView withView:(nullable UIView *)view atScale:(CGFloat)scale

• Uipagecontrol

     @property (nonatomic) nsinteger numberofpages; Set maximum pages //default is 0  @property ( nonatomic) nsinteger currentpage; Set page number // Set a custom picture [self.pagecontrol by KVC Assigning a value to Uipagecontrol's private property Setvalue:[uiimage imagenamed:@ "current"] ForKeyPath:@ "_currentpageimage"]; [self.pagecontrol setvalue:[ UIImage imagenamed:@ "other"] forkeypath:@ "_pageimage"];    

• Nstimer

  Note: Nstimer should be weakWhy Nstimer should be weak, because whenever a Nstimer object is created, the object is referenced by the main line Chengqiang@property (Weaknonatomic) Nstimer *timer;Scheduledtimerwithtimeinterval: Creates a timer and is immediately timedTimeInterval: Interval Time//target: Call Who's method //Selector: What method to call// UserInfo: What parameters to pass //repeats: whether to repeat //every 2 seconds to invoke the self NEXTPAG E method, and does not pass any arguments [Nstimer scheduledtimerwithtimeinterval:2.0 target: Selfselector:@selector (NextPage) UserInfo:nil repeats:YES]; //The main thread handles other events in a little bit of time to handle nstimer [[Nsrunloop Mainrunloop] AddTimer:self. Timer Formode: Nsrunloopcommonmodes];} //As long as the Invalidate method is called, the system will remove Nstimer from the main thread and destroy the Nstimer object [self. Timer invalidate];    

IOS UI Basics 05