初識CALayer之簡易時鐘

#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
@interface ViewController ()
{
    //時針
    UIImageView *m_s;
    //分針
    UIImageView *m_f;
    //秒針
    UIImageView *m_m;
}
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    m_s = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"s"]];
    m_s.frame = CGRectMake(0, 0, 20, 90);
    m_f = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"f"]];
     m_f.frame = CGRectMake(0, 0, 20, 100);
    m_m = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"m"]];
     m_m.frame = CGRectMake(0, 0, 20, 130);
    CALayer *blueLayer = [[CALayer alloc] init];
    blueLayer.frame = CGRectMake(10, 20, 300, 400);
    blueLayer.backgroundColor = [UIColor blueColor].CGColor;
//    把blueLayer的contents屬性設置成圖片。
//    contents
    /* An object providing the contents of the layer, typically a CGImageRef,
     * but may be something else. (For example, NSImage objects are
     * supported on Mac OS X 10.6 and later.) Default value is nil.
     * Animatable.
     
     *對象提供該層的內容，一個典型的cgimageref，
     *但多是別的東西。（例如，nsimage對象
     *後來支持在MAC OS X 10.6和默認值是零。）。
     *動畫。*/
    UIImage *image = [UIImage imageNamed:@"b"];
    blueLayer.contents = (__bridge id)(image.CGImage);
    
    /*
     CALayer與contentMode對應的屬性叫作contentsGravity，可是它是一個NSString類型，而不是像對應的UIKit部分，那裏面的值是枚舉。contentsGravity可選的常量值有如下一些：
     
     kCAGravityCenter
     kCAGravityTop
     kCAGravityBottom
     kCAGravityLeft
     kCAGravityRight
     kCAGravityTopLeft
     kCAGravityTopRight
     kCAGravityBottomLeft
     kCAGravityBottomRight
     kCAGravityResize
     kCAGravityResizeAspect
     kCAGravityResizeAspectFill
     
     和cotentMode同樣，contentsGravity的目的是爲了決定內容在圖層的邊界中怎麼對齊，咱們將使用kCAGravityResizeAspect，它的效果等同於UIViewContentModeScaleAspectFit， 同時它還能在圖層中等比例拉伸以適應圖層的邊界。
     */
    blueLayer.contentsGravity = kCAGravityCenter;

    //    當用代碼的方式來處理寄宿圖的時候，必定要記住要手動的設置圖層的contentsScale屬性，不然，你的圖片在Retina設備上就顯示得不正確啦。代碼以下：
    
    blueLayer.contentsScale = [UIScreen mainScreen].scale;
    
    //    UIView有一個叫作clipsToBounds的屬性能夠用來決定是否顯示超出邊界的內容，
    //CALayer對應的屬性叫作masksToBounds，把它設置爲YES，圖片就在邊界裏了
    blueLayer.masksToBounds = YES;
    
//    [self addSpriteImage:image withContentRect:CGRectMake(0, 0, 1, 1) Layer:blueLayer];
    
//    blueLayer.contentsCenter = CGRectMake(0.25, 0.25, .5, .5);
    
//    self.view.transform = CGAffineTransformMakeRotation(.5);
    
    [self.view.layer addSublayer:blueLayer];
    
    m_s.center = CGPointMake(blueLayer.position.x , blueLayer.position.y);
    m_f.center = CGPointMake(blueLayer.position.x  , blueLayer.position.y);

    m_m.center = CGPointMake(blueLayer.position.x  , blueLayer.position.y);

    m_s.layer.anchorPoint = CGPointMake(.5, .9);
    m_f.layer.anchorPoint = CGPointMake(.5, .9);
    m_m.layer.anchorPoint = CGPointMake(.5, .9);
    [self.view addSubview:m_s];
    [self.view addSubview:m_f];
    [self.view addSubview:m_m];
    [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(tick) userInfo:nil repeats:YES];
    //set initial hand positions
    [self tick];
 }
- (void)tick
{
    //convert time to hours, minutes and seconds
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSUInteger units = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
    NSDateComponents *components = [calendar components:units fromDate:[NSDate date]];
    CGFloat hoursAngle = (components.hour / 12.0) * M_PI * 2.0;
    //calculate hour hand angle //calculate minute hand angle
    CGFloat minsAngle = (components.minute / 60.0) * M_PI * 2.0;
    //calculate second hand angle
    CGFloat secsAngle = (components.second / 60.0) * M_PI * 2.0;
    //rotate hands
    m_s.transform = CGAffineTransformMakeRotation(hoursAngle);
    m_f.transform = CGAffineTransformMakeRotation(minsAngle);
    m_m.transform = CGAffineTransformMakeRotation(secsAngle);
}
/*!
 *  @Author Yunis_song, 15-01-07 16:01:51
 *
 *  @brief  加載圖片切割尺寸，只加載本身想要的部分
 *
 *  @param image 圖片
 *  @param rect  加載圖片剪裁信息
 *  @param layer 圖片加載到哪裏
 */
- (void)addSpriteImage:(UIImage *)image withContentRect:(CGRect)rect Layer:(CALayer *)layer //set image
{
    layer.contents = (__bridge id)image.CGImage;
    
    //scale contents to fit
    layer.contentsGravity = kCAGravityResizeAspect;
    
    //set contentsRect
    //CGRectMake(x, y, w, h) 加載圖片位置
    //x 加載圖片其實x座標  值：0-1，相對位置  0 起始點  0.5 一半起始點
    //y 加載圖片其實y座標  值：0-1，相對位置  0 起始點  0.5 一半起始點
    //w 寬度  值：0-1 1加載所有  0.5 加載通常寬度
    //h 高度  值：0-1 1加載所有  0.5 加載通常高度
    layer.contentsRect = rect;
}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end