Join me to learn about CALayer in charge of iOS (5) Performance

CALayer is very similar to UIView in many aspects. It has location, size, deformation, and content. You can use custom code (usually Core Graphics) to overwrite the rendering method to draw custom content. The hierarchical relationship of a layer is very close to that of a view. You may ask: why are there still separated objects?

The most important answer is that UIView is a heavyweight Object that manages rendering and event processing (especially touch events ). CALayer is all about plotting. In fact, UIView relies on CALayer to manage plotting, so that the two can collaborate well.

Each UIView has a CALayer for plotting. In addition, each CALayer can have child layers, just as each UIView can have child views.