CAReplicatorLayer

CAReplicatorLayer的目的是為了高效生成許多相似的圖層。它會(huì)繪制一個(gè)或多個(gè)圖層的子圖層，并在每個(gè)復(fù)制體上應(yīng)用不同的變換?？瓷先パ菔灸軌蚋咏忉屵@些，我們來寫個(gè)例子吧。

重復(fù)圖層（Repeating Layers）

清單6.8中，我們?cè)谄聊坏闹虚g創(chuàng)建了一個(gè)小白色方塊圖層，然后用CAReplicatorLayer生成十個(gè)圖層組成一個(gè)圓圈。instanceCount屬性指定了圖層需要重復(fù)多少次。instanceTransform指定了一個(gè)CATransform3D3D變換（這種情況下，下一圖層的位移和旋轉(zhuǎn)將會(huì)移動(dòng)到圓圈的下一個(gè)點(diǎn)）。

變換是逐步增加的，每個(gè)實(shí)例都是相對(duì)于前一實(shí)例布局。這就是為什么這些復(fù)制體最終不會(huì)出現(xiàn)在同意位置上，圖6.8是代碼運(yùn)行結(jié)果。

清單6.8 用CAReplicatorLayer重復(fù)圖層

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *containerView;

@end

@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];
    //create a replicator layer and add it to our view
    CAReplicatorLayer *replicator = [CAReplicatorLayer layer];
    replicator.frame = self.containerView.bounds;
    [self.containerView.layer addSublayer:replicator];

    //configure the replicator
    replicator.instanceCount = 10;

    //apply a transform for each instance
    CATransform3D transform = CATransform3DIdentity;
    transform = CATransform3DTranslate(transform, 0, 200, 0);
    transform = CATransform3DRotate(transform, M_PI / 5.0, 0, 0, 1);
    transform = CATransform3DTranslate(transform, 0, -200, 0);
    replicator.instanceTransform = transform;

    //apply a color shift for each instance
    replicator.instanceBlueOffset = -0.1;
    replicator.instanceGreenOffset = -0.1;

    //create a sublayer and place it inside the replicator
    CALayer *layer = [CALayer layer];
    layer.frame = CGRectMake(100.0f, 100.0f, 100.0f, 100.0f);
    layer.backgroundColor = [UIColor whiteColor].CGColor;
    [replicator addSublayer:layer];
}
@end