核心动画还是OpenGL ES？ [英] Core Animation or OpenGL ES?

问题描述

我要执行以下操作：

点击屏幕，在抽点处绘制3个小指。

我从哪里开始？

解决方案

如上所述，Core Graphics框架可能是你想要的。一个好的方法是将UIView子类化，然后覆盖两个方法 drawRect：和 touchesEnded：withEvent：。

当触摸事件在UIView上结束时，可以将事件最后一次触摸的点传递给 touchesEnded：withEvent：



然后，在你的实现 drawRect：，你将得到存储的最后一个触摸点，并使用对 CGContextAddEllipseInRect 的三次调用绘制三个圆圈，如下所述： Quartz 2D编程指南：路径（注册为Apple需要开发人员）。

I want to do the following:

Tap the screen and draw 3 cricles around the the tapped point. Is it better to do this with Core Animation or OpenGL ES?

Where do I start?

解决方案

As mentioned, the Core Graphics framework is probably what you want. A good way to go about it would be to subclass UIView, then override the two methods drawRect: and touchesEnded:withEvent:.

When a touch event ends on the UIView, you can get the point of the last touch from the event passed to touchesEnded:withEvent:, and store it somehow in the instance of your subclassed UIView.

Then, in your implementation of drawRect:, you'll get the stored last touch point, and draw three circles around it using three calls to CGContextAddEllipseInRect, as discussed here: Quartz 2D Programming Guide: Paths (registration as Apple Developer required).

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