学步园

 myLayer.transform.rotation.x=0;

 [myLayer setValue:[NSNumber numberWithInt:0] forKeyPath:@"transform.rotation.x"];

通过delegat: // 一般是layer所在的view

displayLayer: 或 drawLayer:inContext:

触发上面的回调

setNeedsDisplay、setNeedsDisplayInRect:、或者把图层的needsDisplayOnBoundsChange属性设置为YES。

- (void)drawLayer:(CALayer *)theLayer inContext:(CGContextRef)theContext

{

     CGMutablePathRef thePath = CGPathCreateMutable();

     

     CGPathMoveToPoint(thePath,NULL,15.0f,15.f);

     

     CGPathAddCurveToPoint(thePath,

                           NULL,

                           15.f,250.0f,

                           295.0f,250.0f,

                           295.0f,15.0f);

     

     

     CGContextBeginPath(theContext);

     CGContextAddPath(theContext, thePath);

     CGContextSetLineWidth(theContext,

                           

                           [[theLayer valueForKey:@"lineWidth"] floatValue]);

     CGContextStrokePath(theContext);

     

     // release the path

     CFRelease(thePath);

}

6、修改图层内容位置

layer的contentsGravity属性

    当CALayer为一个标识符实现的actionForKey:方法被调用的时候，以下的搜索模式将会被用到:

1. 如果一个图层有委托，那方法actionForLayer:forKey:的实现将会被调用，把图层和行为标识符作为参数。委托的actionForLayer:forKey:的实现需要响应如下:
   • 返回一个行为标识符对应的行为对象。
   • 返回nil，当无法处理行为标识符的时候。
   • 返回NSNull,当无法处理行为标识符，而且搜索需要被终止的时候。
2. 图层的actions字典被搜索以便找到一个和行为标识符对应的对象。
3. 图层的style属性被搜索以便找到一个包含行为标识符的actions字典。
4. 图层类发生一个defaultActionForKey:的消息。它将会返回一个和标识符对应的行为对象，如果不存在的话则返回nil。

代码 1  runActionForKey:object:arguments: 的实现：启动动画

- (void)runActionForKey:(NSString *)key
                 object:(id)anObject
              arguments:(NSDictionary *)dict
{
     [(CALayer *)anObject addAnimation:self forKey:key];
}

重载隐式动画

- (id<CAAction>)actionForLayer:(CALayer *)theLayer
                        forKey:(NSString *)theKey
{
    CATransition *theAnimation=nil;

    if ([theKey isEqualToString:@"contents"])
    {

        theAnimation = [[CATransition alloc] init];
        theAnimation.duration = 1.0;
        theAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
        theAnimation.type = kCATransitionPush;
        theAnimation.subtype = kCATransitionFromRight;
    }

    return theAnimation;
}

代码3的示例使用actions字典模式禁用sublayers属性的默认动画。

// get a mutable version of the current actions dictionary
NSMutableDictionary *customActions=[NSMutableDictionary dictionaryWithDictionary:[theLayer actions]];

// add the new action for sublayers
[customActions setObject:[NSNull null] forKey:@"sublayers"];

// set theLayer actions to the updated dictionary 

8、事务

 隐式事务

显式事务

临时禁用图层的action

[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue
                 forKey:kCATransactionDisableActions];
[aLayer removeFromSuperlayer];
[CATransaction commit];

你可以暂时改变响应改变图层属性的动画的时间，通过设置事务的kCATransactionAnimationDuration键的值为新的时间

[CATransaction begin]; // outer transaction
 
// change the animation duration to 2 seconds
[CATransaction setValue:[NSNumber numberWithFloat:2.0f]
                forKey:kCATransactionAnimationDuration];
// move the layer to a new position
theLayer.position = CGPointMake(0.0,0.0);
 
[CATransaction begin]; // inner transaction
// change the animation duration to 5 seconds
[CATransaction setValue:[NSNumber numberWithFloat:5.0f]
                 forKey:kCATransactionAnimationDuration];
 
// change the zPosition and opacity
theLayer.zPosition=200.0;
theLayer.opacity=0.0;
 
[CATransaction commit]; // inner transaction
[CATransaction commit]; // outer transaction

9、键-值编码兼容的容器类

         return [NSNumber numberWithBool:YES];
 
    return [super defaultValueForKey:key]; 

}