CALayer03——position和anchorPosition

一、基本说明

CALayer 有2个非常重要的属性：position 和 anchorPoint

@property CGPoint position;
用来设置CALayer在父层中的位置
以父层的左上角为原点(0, 0)

@property CGPoint anchorPoint;
称为“定位点”、“锚点”
决定着CALayer身上的哪个点会在position属性所指的位置
以自己的左上角为原点(0, 0)
它的x、y取值范围都是0~1，默认值为（0.5, 0.5）

二、anchorPosition基本图示

如图：
红色图层显示到什么位置，由position属性决定
假设红色图层的position是（100，100）
下图是anchorPostion的位置

图示	图示	图示
anchorPostion(0,0)	anchorPostion(0,0.5)	anchorPostion(0,1)
anchorPostion(0.5,0)	anchorPostion(0.5,0.5)	anchorPostion(0.5,1)
anchorPostion(1,0)	anchorPostion(1,0.5)	anchorPostion(1,1)

三、anchorPosition代码示例

主要代码

//改变anchorPoint
-(void)changeAnchorPoint:(NSInteger)pos{
    CGPoint point = _pointArr[pos].CGPointValue;
    _redView.layer.anchorPoint = point;
}

全部代码

//
//  ViewController.m
//  03_UIView66_anchorPostion
//
//  Created by 杞文明 on 17/6/11.
//  Copyright ? 2017年 杞文明. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIView *redView;
@property (weak, nonatomic) IBOutlet UIView *myCon;

@property (weak, nonatomic) UIButton * lastBtn;

@property (strong, nonatomic) NSArray *pointArr;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    _redView.layer.position = CGPointMake(100, 100);
    [self initPoint];
    [self createButtons];
}

//初始化点
-(void) initPoint{
    NSValue *value1 = [NSValue valueWithCGPoint:CGPointMake(0, 0) ];
    NSValue *value2 = [NSValue valueWithCGPoint:CGPointMake(0, 0.5)];
    NSValue *value3 = [NSValue valueWithCGPoint: CGPointMake(0, 1)];
    NSValue *value4 = [NSValue valueWithCGPoint: CGPointMake(0.5, 0)];
    NSValue *value5 = [NSValue valueWithCGPoint: CGPointMake(0.5, 0.5)];
    NSValue *value6 = [NSValue valueWithCGPoint: CGPointMake(0.5, 1)];
    NSValue *value7 = [NSValue valueWithCGPoint: CGPointMake(1, 0)];
    NSValue *value8 = [NSValue valueWithCGPoint: CGPointMake(1, 0.5)];
    NSValue *value9 = [NSValue valueWithCGPoint: CGPointMake(1, 1) ];

    _pointArr = [[NSArray alloc]initWithObjects:value1,value2,value3,value4,value5,value6,value7,value8,value9, nil];
}

//创建按钮
-(void)createButtons{
    //控件之间的空格
    int MARGIN_WIDTH = 30;
    int width = (_myCon.bounds.size.width-MARGIN_WIDTH*4) / 3;
    int height = 40;

    int j = 0;

    for (int i=0; i<9; i++) {
        j = i/3;
        NSInteger startX = MARGIN_WIDTH + (MARGIN_WIDTH+width)*(i%3);
        NSInteger startY = MARGIN_WIDTH + (MARGIN_WIDTH+height)*j;

        UIButton * button = [[UIButton alloc]initWithFrame:CGRectMake(startX, startY, width, width)];

        //获取对应的point
        CGPoint point = _pointArr[i].CGPointValue;
        NSString * title = [NSString stringWithFormat:@"(%0.1f,%0.1f)",point.x,point.y];
        //给控件设置值和一些属性]
        //文字
        [button setTitle:title forState:UIControlStateNormal];
        //字体颜色
        [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [button setTitleColor:[UIColor greenColor] forState:UIControlStateSelected];


        //给控件点击事件添加代理
        [button addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];

        //设置tag
        [button setTag:i];

        //.把控件添加到myView中
        [_myCon addSubview:button];
    }
}

/**控件的点击事件*/
-(void)clickButton:(UIButton*)button{
    [self changeAnchorPoint:button.tag];
    //选中设置
    if(_lastBtn!=nil)
       [_lastBtn setSelected:NO];
    [button setSelected:YES];
    _lastBtn = button;
}

//改变anchorPoint
-(void)changeAnchorPoint:(NSInteger)pos{
    CGPoint point = _pointArr[pos].CGPointValue;
    _redView.layer.anchorPoint = point;
}
@end

四、anchorPosition图示

五、主要总结

position和anchorPosition总是重合

UIView的center就是CALayer的position