Ios:calayer drawing on the core animation layer

To draw on Calayer:

• To draw on Calayer, there are two methods:1. Create a Calayer subclass, and then overwrite the Drawincontext: method, where you can draw using the Quartz2d API2. Set the Calayer delegate and let delegate implement the Drawlayer:incontext: method to draw• Note:– The UIView can no longer be set to this Calayer delegate because the UIView object is already a delegate of the inner layer, and setting again will cause problems– Regardless of which method you use, you must send a setneedsdisplay message to the layer to trigger a call to the appropriate drawing method relationships between Calayer, UIView, and context:• When UIView receives the Setneedsdisplay message, Calayer prepares a cgcontextref, sends a message to its delegate, UIView, and passes in the prepared Cgcontextref object. UIView in the Drawlayer:incontext: method calls its own DrawRect: Method• Usually in DrawRect: Uigraphicsgetcurrentcontext () is obtained by Calayer incoming Cgcontextref object, in DrawRect: All drawings completed in the Calayer are filled into the cgcontextref, and then copied to the screenCalayer cgcontextref with bitmap contexts (Bitmap Graphics context)let's take a concrete example of both of these plotting methods: mode one : by setting Calayer Proxy and Implementing proxy method Drawlayer:incontext: The form of the drawing//In-(void) viewdidload{[super viewdidload]; The code is:To create a child layer:

    // Create a child layer (using the default anchor point)    Calayer *sublayer = [[Calayer alloc]init];         = CGRectMake (0,0,+);         = Self.view.center;         = [[Uicolor Redcolor]cgcolor];    
    //Set fillet radius, set to 50, at which point the sub-layer is circular      - ;        [Self.view.layer Addsublayer:sublayer];

Set up proxy

    // to set up a proxy    for a layer Sublayer. delegate = self;

Send Redraw message

    // the proxy method is only invoked when the message is sent Setneedsdisplay    [Sublayer Setneedsdisplay];

//Implement proxy Drawlayer:incontext: The method code is:

proxy methods for #pragma mark-calayer-(void) Drawlayer: (Calayer *) layer Incontext: (cgcontextref) ctx{//Draw a rectangleCgcontextaddrect (CTX, CGRectMake (0,0, -, -));
    //Set color CGFloat components[4] = {0.0,1.0,0.0,1.0}; Cgcontextsetstrokecolor (CTX, components);

   This way you can also set the color//cgcontextsetstrokecolorwithcolor (Ctx,[[uicolor greencolor]cgcolor]);   
    //Rotate coordinate systemCGCONTEXTSCALECTM (CTX,1, -1); CGCONTEXTTRANSLATECTM (CTX,0, - -); //draw a smiley face imageUIImage *image = [UIImage imagenamed:@"1.png"]; Cgcontextdrawimage (CTX, CGRectMake (0,0, -, -), [Image Cgimage]); //Draw PathCgcontextdrawpath (CTX, Kcgpathstroke);}

The results are as follows: A smiley face image is drawn in the child layer, and a green-edged rectangle is drawn in the upper-left corner . Method Two : Draw by creating a subclass of Calayer and overriding the Drawincontext: Method//First in the Controller class-(void) viewdidload{[super viewdidload]; The code for creating a child layer in a method is:

#import "ViewController.h"#import "MyLayer.h"@interfaceViewcontroller ()@end@implementationViewcontroller- (void) viewdidload {[Super viewdidload]; //Create a child layerMylayer *mylayer =[[Mylayer alloc]init]; Mylayer.bounds= CGRectMake (0,0, -, -); Mylayer.position= Cgpointmake ( -, -);
    //Set sub-layer background color to gray Mylayer.backgroundcolor=[[Uicolor Graycolor]cgcolor];        [Self.view.layer Addsublayer:mylayer]; [Mylayer Setneedsdisplay];}@end

//Then create a subclass of Calayer, flush the Drawincontext in the class: method, code as follows:

#import "MyLayer.h"#import<UIKit/UIKit.h>@implementationMylayer//Override this method-(void) Drawincontext: (cgcontextref) ctx{//Draw a rectangleCgcontextaddrect (CTX, CGRectMake (0,0, -, -)); //The first way to set the color://Set color space (choose color Scheme: RGB, red, green, blue)Cgcolorspaceref ColorSpace =Cgcolorspacecreatedevicergb (); Cgcontextsetstrokecolorspace (CTX, colorspace);
    ///array of four contents: the first three are red, green, blue, and the latter is the transparency CGFloat components[4] = {0.0,1.0,0.0,1.0};            Cgcontextsetstrokecolor (CTX, components); //This is another simple way to set the color//Cgcontextsetstrokecolorwithcolor (CTX, [[Uicolor Greencolor]cgcolor]); //Draw a stroke pathCgcontextdrawpath (CTX, Kcgpathstroke); //release the Create-out attribute to prevent memory leakscgcolorspacerelease (colorspace);}@end

The results are as follows: A gray layer of layers is created, and a rectangle with a green edge is drawn on it.

Ios:calayer drawing on the core animation layer