繪制矩形/圓形的Objective-C類

Question

我是Ios編程的新手。 我想讓類在我的視圖中繪制和管理矩形/圓形。 所以我嘗試從這里使用解決方案。 當我要繪制一個矩形時，它可以正常工作，但是我想有機會繪制和管理更多的矩形。 因此，將其添加到我的CircleManager.h文件中：

-(void)AddRectangle:(CGRect) rect;
{
//[self drawRect:rect];
[[UIColor blueColor] setFill];
UIRectFill(CGRectInset(self.bounds, 150, 150));
}

然后在我的ViewControler.m添加以下代碼：

- (void)viewDidLoad {  
CircelManager* view = [[CircelManager alloc]initWithFrame:CGRectMake(10, 30, 300, 400)];  
view.backgroundColor = [UIColor blackColor];
[view AddRectangle:CGRectMake(100, 100, 100, 100)];
[self.view addSubview:view];
[super viewDidLoad];   
}

當我嘗試運行此代碼時，會在輸出中得到此代碼：

Jul 11 13:37:38 SG-MacBook-Air.local NavTry1[1730] <Error>: CGContextSetFillColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 11 13:37:38 SG-MacBook-Air.local NavTry1[1730] <Error>: CGContextGetCompositeOperation: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 11 13:37:38 SG-MacBook-Air.local NavTry1[1730] <Error>: CGContextSetCompositeOperation: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 11 13:37:38 SG-MacBook-Air.local NavTry1[1730] <Error>: CGContextFillRects: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Jul 11 13:37:38 SG-MacBook-Air.local NavTry1[1730] <Error>: CGContextSetCompositeOperation: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

我注意到，如果我注釋行[self.view addSubview:view]; 沒有錯誤。

任何幫助將不勝感激。

Answer 1

您應該閱讀蘋果的制圖指南 。 之后，建議您創建一個CAShapeLayer （或將形狀圖層用作layerClass ）。 在圖層上設置UIBezierPath的路徑。 （ UIBezierPath具有創建橢圓和UIBezierPath便捷方法。）

Answer 2

出現錯誤的原因是因為您在沒有繪圖上下文的viewDidLoad進行繪制。 調用AddRectangle:您試圖繪制，而不僅僅是存儲矩形的坐標。 該函數最好命名為drawBlueRect:或類似的名稱。

要使其正常工作：

1. 在UIView子類中移動AddRectangle:
2. 在UIView子類中從drawRect：調用AddRectangle:
3. 從視圖控制器子類中刪除AddRectangle:

UIRectInset的第二個和第三個參數將導致不繪制矩形，因為它會導致矩形的寬度為零。 您還忽略了AddRectangle：中的rect參數，並且始終相對於self.bounds進行繪制。

您不應該自己調用drawRect: 。 如果您應該改為調用setNeedsDisplay ，則在調用drawRect: override時將為您配置圖形上下文。 iOS上的最佳做法是使用CALayers而不是drawRect: ：。 圖層比drawRect:快得多，尤其是對於動畫而言。

我同意Joride的觀點，您應該閱讀他的建議以及適用於iOS的Quartz 2D編程指南 。 取決於您需要的深度級別，有些時候過時了，David Gelphman和Bunny Laden撰寫的《 在Mac OS X中使用Quartz編程：2D和PDF圖形》是Core Graphics的權威指南。