UIGraphicsGetCurrentContext問題

Question

我有一個問題圖紙通過這個圖形上下文

CGContextRef context = UIGraphicsGetCurrentContext(); 

這裏對象是我用來繪製

- (void) draw: (CGContextRef) gc 
{  
    CGFloat black[4] = {0.0f, 0.0f, 0.0f, 1.0f}; // R G B + Alpha 
    CGPoint p [2]; 
    p[0].x = xStart ; 
    p[0].y = yStart ; 
    p[1].x = xEnd ; 
    p[1].y = yEnd ; 
    CGContextSetStrokeColor(gc, black); //Definie la couleur 
    CGContextStrokeLineSegments(gc, p, 2) ; 
} 

一些對象繪製代碼，其他的不要（很奇怪）和在控制檯我讀：

Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextDrawImage: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextSetStrokeColor: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextStrokeLineSegments: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextSetStrokeColor: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextStrokeLineSegments: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextSetStrokeColor: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextStrokeLineSegments: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextSetStrokeColor: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextStrokeLineSegments: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextSetStrokeColor: invalid context 0x0 
Thu Mar 24 21:53:59 MacBook-Air-di-Michele-Giarratana.local IVBricker[381] <Error>: CGContextStrokeLineSegments: invalid context 0x0 

Answer 1

所以我不能說無效的內容錯誤，因爲我們需要看到其餘的代碼，但它看起來像顏色空間可能不正確（默認情況下它不是RGB）。在你調用筆畫之前加上這個：

CGContextSetStrokeColorSpace(gc, CGColorSpaceCreateDeviceRGB());