IOS Calayer (ii)

There is a default Calayer object layer inside the UIView, although we cannot recreate it, but we can add a sub-layer on top of the door.

We know that UIView has Addsubview: methods, similarly, Calayer also have Addsublayer: methods. Our door can be added from the layer by Addsublayer: again there are layers.

Below we show how to add self-layer.

  viewcontroller.m//  Cx-calayer (ii)////  Created by Ma C on 16/3/19.//  Copyright 2016 Xubaoaichiyu . All rights reserved.//#import "ViewController.h" @interface Viewcontroller () @end @implementation viewcontroller-(void ) Viewdidload {    [super viewdidload];    Initialize layer    calayer * layer = [[Calayer alloc]init];    Set Layer frame    layer.frame = CGRectMake (0, Self.view.frame.size.width, max);    Sets the background color of the layer    Layer.backgroundcolor = [Uicolor Orangecolor]. Cgcolor;    Add layer on Self.view.layer    [Self.view.layer addsublayer:layer];        } @end

In addition to this simple layer, we can also set the layer of the picture. (layer.contents = (ID) [UIImage imagenamed:@ "Nvshen.jpg"]. Cgimage;)

  viewcontroller.m//  Cx-calayer (ii)////  Created by Ma C on 16/3/19.//  Copyright 2016 Xubaoaichiyu . All rights reserved.//#import "ViewController.h" @interface Viewcontroller () @end @implementation viewcontroller-(void ) Viewdidload {    [super viewdidload];    Initialize layer    calayer * layer = [[Calayer alloc]init];    Set Layer frame    layer.frame = CGRectMake (0, Self.view.frame.size.width, self.view.frame.size.height);    Add picture    layer.contents = (ID) [UIImage imagenamed:@ "Nvshen.jpg"]. Cgimage;    Sets the background color of the layer    Layer.backgroundcolor = [Uicolor Orangecolor]. Cgcolor;    Add layer on Self.view.layer    [Self.view.layer addsublayer:layer];        } @end

The following is a reference to MJ God's explanation:

Why use the 2 data types Cgcolorref and Cgimageref in Calayer instead of Uicolor and uiimage?

* First of all to know: Calayer is defined in the Quartzcore framework, CGIMAGEREF, cgcolorref two data types are defined in the Coregraphics framework; Uicolor, UIImage is defined in the Uikit frame

* Second, the Quartzcore framework and the Coregraphics framework are available across platforms and can be used on both iOS and Mac OS x, but Uikit can only be used in iOS

* Therefore, in order to ensure portability, quartzcore can not use UIImage, Uicolor, can only use Cgimageref, Cgcolorref

* However, in many cases, the Coregraphics object can be obtained by Uikit the specific method of the object, such as UIImage Cgimage method can return a cgimageref

Choice of UIView and Calayer

* In fact, compared with the Calayer,uiview more than one event processing function. In other words, Calayer cannot handle user touch events, and UIView can

* So, if the displayed things need to interact with the user, with UIView, if you do not need to interact with the user, with UIView or Calayer can

* Of course, calayer performance will be higher because it is less event-handling, more lightweight

Other relationships between UIView and Calayer

* UIView can access all sub-views through the Subviews property, similarly, Calayer can access all child layers through the Sublayers property

* UIView can access the parent view through the Superview property, similarly, Calayer can also access the parent layer through the Superlayer property

* See below for a diagram of UIView and Calayer:

If two UIView is a parent-child relationship, then the Calayer within them is also a parent-child relationship.

IOS Calayer (ii)