为绘图应用程序生成层结构

下面是我在几分钟内为自定义视图编写的一些工作代码,希望能有所帮助。它创建了10个绿色层,并将它们设置为每秒不同位置的动画。

MBLineLayerDelegate *lineLayerDelegate;
@property (nonatomic, retain) NSMutableArray *ballLayers;

- (void)awakeFromNib
{
    self.ballLayers = [NSMutableArray array];
    lineLayerDelegate = [[MBLineLayerDelegate alloc] init];
    for (NSUInteger i = 0; i < 10; i++) {
        CALayer *ball = [CALayer layer];
        CGFloat x = self.bounds.size.width * (CGFloat)random()/RAND_MAX;
        CGFloat y = self.bounds.size.height * (CGFloat)random()/RAND_MAX;
        ball.frame = CGRectMake(x, y, 20, 20);
        ball.backgroundColor = [UIColor greenColor].CGColor;
        ball.delegate = lineLayerDelegate;
        [self.layer addSublayer:ball];
        [self.ballLayers addObject:ball];
    }

    [self performSelector:@selector(animateBallsToRandomLocation) withObject:nil afterDelay:0];
}

- (void)animateBallsToRandomLocation
{
    for (CALayer *layer in self.ballLayers) {
        CGFloat x = self.bounds.size.width * (CGFloat)random()/RAND_MAX;
        CGFloat y = self.bounds.size.height * (CGFloat)random()/RAND_MAX;
        layer.position = CGPointMake(x, y);
    }
    [self performSelector:@selector(animateBallsToRandomLocation) withObject:nil afterDelay:1];
}

下面是CALayer代表的一些代码,用来画一条线:

@interface MBLineLayerDelegate : NSObject {
}
- (void)drawLayer:(CALayer*)layer inContext:(CGContextRef)ctx;
@end

@implementation MBLineLayerDelegate

- (void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context
{
        CGRect rect = layer.bounds;
        CGContextSaveGState(context);

        CGContextTranslateCTM(context, 0.0, rect.size.height);
        CGContextScaleCTM(context, 1.0, -1.0);
        CGContextSetAllowsAntialiasing(context, YES);
        CGContextSetShouldAntialias(context, YES);

        CGContextMoveToPoint(context, 0, 0);
        CGContextAddLineToPoint(context, rect.size.width, rect.size.height);

        CGContextRestoreGState(context);
}

@end