给UIButton设置阴影及动画组

        //设置“开启旅程”按钮
        UIButton *startBtn = self.startBtn;
        CGFloat btnW = 100;
        CGFloat btnH = 35;
        CGFloat btnX = (self.dataArray.count) * CGRectGetWidth(self.frame) + self.coreView.bounds.size.width/2-btnW/2;
        CGFloat btnY = self.coreView.bounds.size.height * 0.9;
        startBtn.frame = CGRectMake(btnX, btnY, btnW, btnH);
        [startBtn setTitle:@"开启旅程" forState:UIControlStateNormal];
        [startBtn setTitleColor:[UIColor lightTextColor] forState:UIControlStateHighlighted];
        [startBtn addTarget:self action:@selector(startBtnClicked) forControlEvents:UIControlEventTouchUpInside];
        startBtn.titleLabel.font = [UIFont boldSystemFontOfSize:18];
        startBtn.backgroundColor=[UIColor colorWithRed:44/255.0 green:178/255.0 blue:219/255.0 alpha:1];
        startBtn.layer.cornerRadius = 8;
        startBtn.layer.shadowOffset =  CGSizeMake(1, 1);
        startBtn.layer.shadowOpacity = 0.8;
        startBtn.layer.shadowColor =  [UIColor blackColor].CGColor;
        [self.coreView addSubview:startBtn];
        //"开启旅程"按钮动画
        CAAnimationGroup *group = [CAAnimationGroup animation];
        group.duration = 0.7;
        group.repeatCount = 1;
        CABasicAnimation *anima1 = [CABasicAnimation animation];
        anima1.keyPath = @"opacity";
        anima1.toValue = @0;
        CABasicAnimation *anima2 = [CABasicAnimation animation];
        anima2.keyPath = @"transform.scale";
        anima2.toValue = @2.5;
        group.animations = @[anima1, anima2];
        [_startBtn.layer addAnimation:group forKey:nil];