IOS Quartz2D自定义view

@property (nonatomic, weak) UIImageView *imageView;
@property (nonatomic, weak) NJImageView *njIv;
@end

@implementation NJViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    /*
    UIImageView *iv = [[UIImageView alloc] init];
    iv.image = [UIImage imageNamed:@"me"];
    iv.frame = CGRectMake(100, 100, 100, 100);
    [self.view addSubview:iv];
    self.imageView = iv;
     */

    NJImageView *njIv = [[NJImageView alloc] init];
    njIv.image = [UIImage imageNamed:@"me"];
    njIv.frame = CGRectMake(, , , );
    [self.view addSubview:njIv];
    self.njIv = njIv;

    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(, , , )];
    [btn addTarget:self action:@selector(btnClick) forControlEvents:UIControlEventTouchUpInside];
    [btn setTitle:@"点点大家的疯狂的教科书" forState:UIControlStateNormal];
    [btn setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    [self.view addSubview:btn];
}

- (void)btnClick
{
    NSLog(@"btnClick");

    // 创建一张新的图片替换原有图片
    UIImage *image = [UIImage imageNamed:@"psb.jpeg"];

    // self.imageView.image = image;
    self.njIv.image = image;
}

@implementation NJImageView

@property (nonatomic, strong) UIImage *image;
- (void)drawRect:(CGRect)rect
{
    // Drawing code

    [self.image drawInRect:rect];
}

-(void)setImage:(UIImage *)image
{
    _image = image;

    [self setNeedsDisplay];
}

@end