直觀上來看，通過壹個UIView配合圖片，或者半透明的顏色都可以，這樣的確可以簡單的實現這個過程。但是比較推薦使用通過Quartz2D去實現這個功能，涉及到圖片素材的加載，還是有性能影響的。IO過程耗費比較高。貼壹個實現:-(void)drawRect:(CGRect)rect{CGContextRefcontext=UIGraphicsGetCurrentContext();CGRectcurrentBounds=self.bounds;CGGradientRefbackgroundGradient;size_tnum_locations=2;CGFloatlocations[2]={0.0,1.0};CGFloatcomponents[8]={0.0,0.0,0.0,0.0,//Startcolor0.0,0.0,0.0,0.6};//EndcolorCGColorSpaceRefrgbColorspace=CGColorSpaceCreateDeviceRGB();backgroundGradient=CGGradientCreateWithColorComponents(rgbColorspace,components,locations,num_locations);CGPointcenterPoint=CGPointMake(CGRectGetMidX(currentBounds),CGRectGetMidY(currentBounds));CGContextDrawRadialGradient(context,backgroundGradient,centerPoint,0.0,centerPoint,currentBounds.size.width,kCGGradientDrawsAfterEndLocation);CGGradientRelease(backgroundGradient);}在UIView子類的drawRect中實現即可。
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