IOS Programming views:redrawing and Uiscrollview

Last Update:2015-05-07 Source: Internet

Author: User

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IOS Programming views:redrawing and uiscrollview?1.1 event?You is going to see what views is redrawn in response to an Event.You will see how the view responds to the Event.You declared properties in header Files. You can also declare the properties in class Extensions.You can declare a property in the header file, or you can declare it in class Extensions.#import "BNRHypnosisView.h"@interface Bnrhypnosisview ()@property (strong, Nonatomic) Uicolor *circlecolor;@end@implementation Bnrhypnosisview?These three lines of code is a class extension with one property Declaration.There are three lines of code in a class Extension.?When the user touches a view, The view is sent the message touchesbegan:withevent:.When the user touches a view, The view sends a message to Tochesbegan:withevent:?Override touchesBegan:withEvent:to Change the Circlecolor property of the view to a random Color.Overriding the Touchesbegan:withevent methodWhen a finger touches the screen -(void) touchesbegan: (nsset *) touches withevent: (uievent *) Event{ NSLog (@ "%@ was touched", self);Get 3 random numbers between 0 and 1 float red = (arc4random ()% 100)/100.0; float green = (arc4random ()% 100)/100.0; float blue = (arc4random ()% 100)/100.0;Uicolor *randomcolor = [uicolor colorwithred:red green:greenBlue:blue alpha:1.0];Self.circlecolor = randomcolor; }1.2 Run loop and redrawing views loop and redraw viewsWhen an IOS application is launched, It starts a run loop. The run loop ' s job is to listen for events, such as a Touch.When an iOS application starts, it starts Looping. Run Loop ' s job is to listen for events such as TouchWhen a event occurs, the run loop then finds the appropriate handler methods for the Event. Those handler methods call other methods, which call more methods, and so On. Once all of the methods has completed, control returns to the run Loop.When the event occurs, run Loop will find the appropriate handler method to handle the Event. This handler handles other methods and calls more METHODS. Until all the methods have been completed, control is back to run Loop.When the run loop regains control, it checks a list of ' dirty views ' –views that need to being re-rendered based on what Ha Ppened in the recent round of event Handling.When run loop is regain control, it detects a series of dirty views-views according to the recent event handling what happened to REDRAW.The run loop then sends the drawrect:message to the "this" list before all of the views in the hierarchy is compo Sited together Again.Before all of the view is re-assembled, the run loop sends a message to the DrawRect method of the view in the List.Batching the redrawing of views on the end of a run loop cycle prevents needlessly redrawing a view more than once if more than one of its properties are changed in a single event.Batch processing redrawing of views at the end of the run loop, you can save a lot of Time.To get a view on the list of dirty views, you must send it the message setneedsdisplay.In order for an views to be added to the dirty views list, you should send Setneedsdisplay to the VIEW.The subclasses of UIView that is part of the IOS SDK send themselves setneedsdisplay whenever their content changes.The UIView subclasses within the iOS SDK will send themselves setneedsdisplay whenever their content changes.In the custom UIView subclasses, like bnrhypnosisview, You must send this message yourself.?In bnrhypnosisview.m, implement a custom accessor for the Circlecolor property to send Setneedsdisplay to the view Wheneve R is Changed.In our example, we set the Setneedsdisplay in the accessor set Method.-(void) setcirclecolor: (uicolor *) circlecolor{ _circlecolor = circlecolor;[self setneedsdisplay]; }1.3 Class Extensions?What's the difference between a property declared in a class extension and one declared in a header file?Declare the class extension and in header file?A class ' s header file is the visible to other Classes. that, in fact, was its purpose. A class declares properties and methods in their header file to advertise to other classes how they can interact with the CL or its instances.A variable declared in the header file can be called by another class. This is also its purpose.Properties and methods that is used internally by the class belong in a class Extension.A property or method can be called in a class extension only if it is internal.It is good practice to keep your header file as brief as it Can. This makes it easier for others to understand how they can use your class.It's a good habit to keep the header file size Small. Make it easier for others to understand your class.?A class extension looks a little like a header file. It begins with @interface followed by an empty set of Parentheses. The @end marks the end of the class Extension.A class extension @interface begins, followed by the class name, followed by an empty Parenthesis.2.1 UiscrollviewScroll views is typically used for views of that is larger than the Screen. A scroll view draws a rectangular portion of its subview, and moving your finger, or panning, on the scroll view changes T He position of that rectangle on the SUBVIEW.Scroll views are used as those larger than the Screen. A scroll view painting part of its SUBVIEW. When you move your finger over the scroll view, the position of the rectangle on the subview is Changed.Thus, you can think of the scroll view as a viewing port so you can move aroundScroll view can therefore be viewed as a view port.The size of the scroll view is the size of this viewing port.The size of the scroll view is the part of the view that you see.The size of the area so it can be used to view are the Uiscrollview ' s contentsize, which is typically the size of the UIS Crollview ' s SUBVIEW.And you can use the size of the view is Uiscrollview contentsize, which is the size of Uiscrollview SUBVIEW.Create Cgrects for Frames CGRect Screenrect = self.window.bounds; CGRect Bigrect = screenrect; BigRect.size.width *= 2.0; BigRect.size.height *= 2.0;Create a screen-sized scroll view and add it to the windowUiscrollview *scrollview = [[uiscrollview alloc] initwithframe:screenrect];[self.window addsubview:scrollview];Create a super-sized hypnosis view and add it to the scroll viewBnrhypnosisview *hypnosisview = [[bnrhypnosisview alloc] initwithframe:bigrect];[scrollView addsubview:hypnosisview];The scroll view how big it content area is Scrollview.contentsize = bigrect.size;?2.2 Panning and paging?Another use for a scroll view is panning between a number of view Instances.Another application of scroll view is the panning (which should be the meaning of the Switch) view Instances.?Create a screen-sized Hypnosis view and add it to the scroll view bnrhypnosisview *hypnosisview = [[bnrhypnosisview All oc] [initwithframe:screenrect];?To force the scroll view to snap their viewing port to one of the views, turn on paging for the scroll view in Bnrappdelegat e.m.Sometimes you do not want the picture to stop in the middle position, you can use pagingenabled =yes;Uiscrollview *scrollview = [[uiscrollview alloc] initwithframe:screenrect]; scrollview.pagingenabled = YES; [self.window addsubview:scrollview];?Paging works by taking the size of the scroll view ' s?bounds?and dividing up the?contentsize?it displays into sections of T He same size.Pagination is displayed as a sub-section of the same size by obtaining the bounds of the scroll view and dividing it into contentsize.?After the user pans, the view port would scroll to show only one of the these Sections.The view port displays only one of these sections when the user is flipping back and forth.?IOS Programming views:redrawing and Uiscrollview

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