如何在iOS 11.4上以编程方式更改卷

以前,我使用这种方法以编程方式设置音量：

MPVolumeView *volumeView = [[MPVolumeView alloc] init];
UiSlider *volumeViewSlider = nil;

for (UIView *view in [volumeView subviews])
{
    if ([view.class.description isEqualToString:@"MPVolumeSlider"])
    {
        volumeViewSlider = (UiSlider *)view;
        break;
    }
}

[volumeViewSlider setValue:0.5 animated:YES];
[volumeViewSlider sendActionsForControlEvents:UIControlEventTouchUpInside];

直到iOS 11.4它运行良好(即使在iOS 11.3上),但在iOS 11.4上却没有.体积值保持不变.有人可以帮助解决这个问题吗？谢谢.

解决方法

在一小段延迟后更改volumeViewSlider.value可以解决问题.

- (IBAction)increase:(id)sender {
  MPVolumeView *volumeView = [[MPVolumeView alloc] init];
  UiSlider *volumeViewSlider = nil;

  for (UIView *view in volumeView.subviews) {
    if ([view isKindOfClass:[UiSlider class]]) {
      volumeViewSlider = (UiSlider *)view;
      break;
    }
  }

  dispatch_after(dispatch_time(disPATCH_TIME_Now,(int64_t)(0.01 * NSEC_PER_SEC)),dispatch_get_main_queue(),^{
    volumeViewSlider.value = 0.5f;
  });
}

Swift version