@property(nonatomic,strong)CAGradientLayer* gradientLayer;

self.gradientLayer= [CAGradientLayerlayer];//设置渐变效果

//self.gradientLayer.borderWidth = 0;

self.gradientLayer.frame=CGRectMake(0,0,SCREEN_WIDTH,self.gradientView.bounds.size.height);

self.gradientLayer.colors=@[(__bridgeid)[UIColorclearColor].CGColor,

(__bridgeid)[UIColorblackColor].CGColor];

self.gradientLayer.startPoint=CGPointMake(0,0);

self.gradientLayer.endPoint=CGPointMake(0,1);

//self.gradientLayer.locations = @[@(0.5f) ,@(1.0f)];

[self.view.layeraddSublayer:self.gradientLayer];