如何让UIImageView动画高效节能？

Question

所以我在我的代码中有这个方法，它在我的应用程序中显示了一个非常好的加载器。我被告知的最好的方法就是使用UIImageView。

我设置了所有的参数，我想我已经覆盖了我需要的一切。加载器继续在我的应用程序的后台“旋转”，相应的UI元素根据我何时需要显示加载器来调整它们的alpha，在这种情况下是UITableView。

然而，当在iOS 7上进行测试并分析能源诊断和时间分析时，我发现这个应用程序占用了很多资源。有没有办法让这件事更有效率呢？

- (void)displayLoadingCircle:(BOOL)display {

    UIView *placeholderView = [[UIView alloc] initWithFrame:self.view.bounds];
    UIImageView* animatedImageView = [[UIImageView alloc] initWithFrame:CGRectMake(94, 240, 125, 125)];
    [animatedImageView setContentMode:UIViewContentModeScaleToFill];
    [animatedImageView setAlpha:0.7f];

    animatedImageView.animationImages = [NSArray arrayWithObjects:
                                         [UIImage imageNamed:@"loader-1 (dragged).png"],
                                         [UIImage imageNamed:@"loader-2 (dragged).png"],
                                         [UIImage imageNamed:@"loader-3 (dragged).png"],
                                         [UIImage imageNamed:@"loader-4 (dragged).png"],
                                         [UIImage imageNamed:@"loader-5 (dragged).png"],
                                         [UIImage imageNamed:@"loader-6 (dragged).png"],
                                         [UIImage imageNamed:@"loader-7 (dragged).png"],
                                         [UIImage imageNamed:@"loader-8 (dragged).png"],
                                         [UIImage imageNamed:@"loader-9 (dragged).png"],
                                         [UIImage imageNamed:@"loader-10 (dragged).png"],
                                         [UIImage imageNamed:@"loader-11 (dragged).png"],
                                         [UIImage imageNamed:@"loader-12 (dragged).png"],
                                         [UIImage imageNamed:@"loader-13 (dragged).png"],
                                         [UIImage imageNamed:@"loader-14 (dragged).png"],
                                         [UIImage imageNamed:@"loader-15 (dragged).png"],
                                         [UIImage imageNamed:@"loader-16 (dragged).png"],
                                         [UIImage imageNamed:@"loader-17 (dragged).png"],
                                         [UIImage imageNamed:@"loader-18 (dragged).png"],
                                         [UIImage imageNamed:@"loader-19 (dragged).png"],
                                         [UIImage imageNamed:@"loader-20 (dragged).png"],
                                         [UIImage imageNamed:@"loader-21 (dragged).png"],
                                         [UIImage imageNamed:@"loader-22 (dragged).png"],
                                         [UIImage imageNamed:@"loader-23 (dragged).png"],
                                         [UIImage imageNamed:@"loader-24 (dragged).png"],
                                         [UIImage imageNamed:@"loader-25 (dragged).png"],
                                         [UIImage imageNamed:@"loader-26 (dragged).png"],
                                         [UIImage imageNamed:@"loader-27 (dragged).png"],
                                         [UIImage imageNamed:@"loader-28 (dragged).png"],
                                         [UIImage imageNamed:@"loader-29 (dragged).png"],
                                         [UIImage imageNamed:@"loader-30 (dragged).png"], nil];
    animatedImageView.animationDuration = 0.55f;
    animatedImageView.animationRepeatCount = 0;
    [animatedImageView startAnimating];
    [placeholderView addSubview:animatedImageView];
    [self.view insertSubview:placeholderView belowSubview:_tweetTable];
    self.placeholderView = placeholderView;

    _tweetTable.alpha = 0.0f;

}

Answer 1

原来我的帧率太高了(60fps)，这使得iPhone做了太多的工作。将30帧的持续时间减少到1.0f，将每秒的帧数减少到30fps，这解决了我的问题。