setNeedsDisplay不适用于UIImageView的子类

import UIKit
class CustomView: UIView {
    override func drawRect(rect: CGRect) {
        print("Draw")
    }
}

Drag a UIView, set its class to be CustomView, create a reference customView to it.

拖动UIView，将其类设置为CustomView，为其创建引用customView。

When I call customView.setNeedsDisplay(), drawRect of CustomView get called.

当我调用customView.setNeedsDisplay（）时，调用CustomView的drawRect。

import UIKit
class CustomImageView: UIImageView {
    override func drawRect(rect: CGRect) {
        print("DrawImage")
    }
}

Drag a UIImageView, set its class to be CustomImageView, create a reference customImageView to it.

拖动一个UIImageView，将其类设置为CustomImageView，为它创建一个引用customImageView。

When I call customImageView.setNeedsdisplay(), nothing happen. Why?

当我调用customImageView.setNeedsdisplay（）时，什么都没发生。为什么？

1 个解决方案

#1

The UIImageView class is optimized to draw its images to the display. UIImageView does not call the drawRect: method of its subclasses. If your subclass needs to include custom drawing code, you should subclass the UIView class instead.

UIImageView类经过优化，可将其图像绘制到显示器上。 UIImageView不调用其子类的drawRect：方法。如果您的子类需要包含自定义绘图代码，则应该替代UIView类。