self.loginBtn.layer.shadowOffset = CGSizeMake(0, 0);
self.loginBtn.layer.shadowColor = [UIColor redColor].CGColor;
self.loginBtn.layer.shadowRadius = 150;
self.loginBtn.layer.shadowOpacity = 1;
shadowOffset
偏移量shadowColor
顏色shadowRadius
陰影擴散的半徑shadowOpacity
陰影的透明度