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iPhone 自定义 ui 组件

发布于 2024-10-20 12:16:44 字数 247 浏览 1 评论 0原文

我对 iPhone 开发非常陌生。

我想创建一个可以包含正方形、圆形或三角形的 ui 组件。我将向其构造函数传递一个参数来说明我想要什么样的形状。

我希望这个物体可以通过加速度计或用户的手指移动。我也想把它变大或变小。

我想过创建一个继承 UIView 的自定义 UI 组件。

我不知道如果我用 Quartz 2D 绘制一个形状，它的行为会像 UI 组件一样。

我可以这样做吗？您有更好的解决方案吗？

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鲜血染红嫁衣 2024-10-27 12:16:44

我认为简单而常规的解决方案是子类化 UIView。这就是你要做的事。

从概念上讲，UIView 通过绘制它们来保留其视觉内容。（大多数情况下使用Quartz！）视觉内容是否发生变化？ UIView 只是重新绘制它们。当您更改任何内容时，UIView 会重新绘制所有内容。（当然，这是概念性描述，实际情况有很大不同，因为有大量优化）

但是重要的一点是您要做的只是覆盖一个方法。因为 UIKit 代替您完成了大部分重要的优化。

UIView 使用 - (void)drawRect:(CGRect)rect 方法绘制其视觉内容。您可以重写此方法来绘制形状。如果您在此方法中绘制某些内容，该形状将绘制在透明视图上。

如果您操作视图（缩放、移动、旋转...）UIKit 可能会请求视图重绘其图形。并且，视图将调用绘制形状的方法。这是非常常规的技术。大多数自定义图形和动画都是用这种方法构建的。您所要做的只是在方法 - (void)drawRect:(CGRect)rect 中编写绘图代码。

参考文档中有关于这个概念的很好的指南：

并注意您必须使用通过调用 UIGraphicsGetCurrentContext 检索的 CGContextRef 进行绘制（空白 ); 方法而不是创建您自己的方法。上下文表示实际设备屏幕。如果您创建自己的上下文，则它们都无法提供实际的设备屏幕。

举个例子：

@interface MyView : UIView
@end

@implementation MyView
- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    // Do your drawing here with the `context`.
    // And don't release it because the it is not yours, just borrowed from `UIKit`.
}
@end

也许您需要某种形式的优化。 UIKit 进行基本的优化，但不是全部。因为图形优化在内存和处理之间有很多权衡。您可以从 CALayer 和 shouldRasterize 获得一些优化。但是，如果您需要更多，则必须开始研究实时图形。

I think simple and regular solution is subclassing UIView. Just what you're going to do.

Conceptually, UIView is keep its visual content by drawing them. (with Quartz in most cases!) If the visual content changed? UIView just re-draws them. When you change anything, UIView re-draws everything. (Of course, this is conceptual description, real is a lot differ because there are heavy optimizations)

However the important point is what you have to do for this is just overriding a method. Because UIKit does most of important optimizations instead of you.

UIView draws its visual content with - (void)drawRect:(CGRect)rect method. And you can override this method to draw your shapes. If you draw something in this method, the shape will be drawn on the transparent view.

If you manipulate the view (scaling, move, rotate...) UIKit may request the view to redraw its graphics. And, the view will recall the method to draw your shape. This is very regular technique. Most custom graphics and animation built with this method. All what you have to do is just writing drawing code in the method - (void)drawRect:(CGRect)rect.

There're good guides about this concept on reference documentation:

And take care about you have to draw with CGContextRef retrieved by calling UIGraphicsGetCurrentContext ( void ); method instead of creating your own. The context means actual device screen. If you make your own context, none of them can offer actual device screen.

As an example:

@interface MyView : UIView
@end

@implementation MyView
- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    // Do your drawing here with the `context`.
    // And don't release it because the it is not yours, just borrowed from `UIKit`.
}
@end

Maybe you'll need a sort of optimization in any form. UIKit does basic optimizations but not everything. Because graphic optimization has many trade-offs between memory and processing. You can gain a few optimization from CALayer and shouldRasterize. However if you need more, you have to start studying about real-time graphics.

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