iphone - UIImagePickerController 创建挂起几秒钟

Question

我试图在 UIActionSheet 中单击按钮后显示 UIImagePickerController。代码很简单。但是，对 [[UIImagePickerController alloc] init] 的调用在完成之前会挂起几秒钟。我在模拟器中没有看到这种行为，但在 iPod 和 iPhone 上看到了。

以下是 UIActionSheetDelegate 方法。添加日志消息以显示执行时间。

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
    NSLog(@"Action sheet clicked button at index %d", buttonIndex);
    switch (buttonIndex) {
        case kSelectFromCameraButtonIndex:
            [self showImagePickerWithCamera];
            break;
        case kSelectFromPhotoLibraryButtonIndex:
            [self showImagePickerWithPhotoLibrary];
            break;
    }
}

- (void)actionSheet:(UIActionSheet *)actionSheet willDismissWithButtonIndex:(NSInteger)buttonIndex {
    NSLog(@"Action sheet will dismiss with button index %d", buttonIndex);
}

- (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex {
    NSLog(@"Action sheet did dismiss with button index %d", buttonIndex);
}

这是实际创建 UIImagePickerController 的代码:

- (void)showImagePickerWithPhotoLibrary {
    NSLog(@"Showing image picker with photo library");
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {

        NSLog(@"Creating picker");
        UIImagePickerController *picker = [[UIImagePickerController alloc] init];

        NSLog(@"Setting picker settings");
        picker.delegate = self;
        picker.allowsEditing = YES;
        picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

        NSLog(@"Presenting picker as modal view controller");
        [self presentModalViewController:picker animated:YES];

        NSLog(@"Releasing picker");
        [picker release];
    }
}

没什么特别的事情发生。但是，如果您查看控制台输出，您会注意到创建 UIImagePickerController 的行大约需要 7 秒才能完成。

2010-09-21 15:23:26.107 Oh Snap[1264:307] Action sheet clicked button at index 1
2010-09-21 15:23:26.113 Oh Snap[1264:307] Showing image picker with photo library
2010-09-21 15:23:26.120 Oh Snap[1264:307] Creating picker
2010-09-21 15:23:33.111 Oh Snap[1264:307] Setting picker settings
2010-09-21 15:23:33.123 Oh Snap[1264:307] Presenting picker as modal view controller
2010-09-21 15:23:33.136 Oh Snap[1264:307] Using two-stage rotation animation. To use the smoother single-stage animation, this application must remove two-stage method implementations.
2010-09-21 15:23:33.144 Oh Snap[1264:307] Using two-stage rotation animation is not supported when rotating more than one view controller or view controllers not the window delegate
2010-09-21 15:23:33.289 Oh Snap[1264:307] Releasing picker
2010-09-21 15:23:33.299 Oh Snap[1264:307] Action sheet will dismiss with button index 1
2010-09-21 15:23:33.916 Oh Snap[1264:307] Action sheet did dismiss with button index 1

有谁知道这是什么原因造成的吗？

Answer 1

我注意到在我的应用程序中 UIImagePickerController 需要很长时间才能创建。解决方法是在需要之前实例化它，即使在单独的线程上也是如此，然后在需要时呈现它。我猜想但无法确认这就是 Apple 使其速度相当快的方式。