7.2 完成塊

完成塊

基于UIView的block的動(dòng)畫允許你在動(dòng)畫結(jié)束的時(shí)候提供一個(gè)完成的動(dòng)作。CATranscation接口提供的+setCompletionBlock:方法也有同樣的功能。我們來調(diào)整上個(gè)例子，在顏色變化結(jié)束之后執(zhí)行一些操作。我們來添加一個(gè)完成之后的block，用來在每次顏色變化結(jié)束之后切換到另一個(gè)旋轉(zhuǎn)90的動(dòng)畫。代碼見清單7.3，運(yùn)行結(jié)果見圖7.2。

清單7.3 在顏色動(dòng)畫完成之后添加一個(gè)回調(diào)

- (IBAction)changeColor
{
    //begin a new transaction
    [CATransaction begin];
    //set the animation duration to 1 second
    [CATransaction setAnimationDuration:1.0];
    //add the spin animation on completion
    [CATransaction setCompletionBlock:^{
        //rotate the layer 90 degrees
        CGAffineTransform transform = self.colorLayer.affineTransform;
        transform = CGAffineTransformRotate(transform, M_PI_2);
        self.colorLayer.affineTransform = transform;
    }];
    //randomize the layer background color
    CGFloat red = arc4random() / (CGFloat)INT_MAX;
    CGFloat green = arc4random() / (CGFloat)INT_MAX;
    CGFloat blue = arc4random() / (CGFloat)INT_MAX;
    self.colorLayer.backgroundColor = [UIColor colorWithRed:red green:green blue:blue alpha:1.0].CGColor;
    //commit the transaction
    [CATransaction commit];
}