以下代码在iPad上运行时崩溃并显示错误消息：
（＆lt; UIPopoverPresentationController：0x1377a19e0＆gt;）应该是非零的 在演示文稿发生之前设置的sourceView或barButtonItem。＆＃39;
但是，在我的代码中我有以下内容，我检查了断点和控制台打印，以确保sourceview和barbutton不是nil。我需要做些什么才能避免这种情况？该错误仅出现在iPad上。这是造成麻烦的方法：
- (void)showChooseImageOptions {
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];
UIAlertAction *chooseAction = [UIAlertAction actionWithTitle:@"Choose From Photos" style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action) {
[self showLibrary];
}];
UIAlertAction *takeAction = [UIAlertAction actionWithTitle:@"Take Photo" style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action) {
[self showCamera];
}];
self.directionsTextView.text=@"";
[alertController addAction:chooseAction];
[alertController addAction:takeAction];
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
if (self.imageView.image) {
self.directionsTextView.text=@"Tap the circle to change the image";
} else{
self.directionsTextView.text=@"Tap the blue circle to choose or take an image";
}
}];
[alertController addAction:cancelAction];
alertController.view.tintColor=[ColorSuperclass returnApplicationMainColor];
alertController.popoverPresentationController.barButtonItem = self.navigationItem.rightBarButtonItem;
if ( [alertController respondsToSelector:@selector(popoverPresentationController)] ) {
// at least iOS8
alertController.popoverPresentationController.sourceView = self.view;
}
[self presentViewController:alertController animated:YES completion:nil];
}
方法showCamera和showLibrary只是：
-(void)showCamera {
if (TARGET_IPHONE_SIMULATOR) {
//do nothing, the simulator cannot handle pressing the take photos...
} else{
[self showImagePickerForSourceType:UIImagePickerControllerSourceTypeCamera];
}
}
- (void)showLibrary {
[self showImagePickerForSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
}
和show source类型方法：
- (void)showImagePickerForSourceType:(UIImagePickerControllerSourceType)sourceType {
UIImagePickerController *imagePickerController = [[UIImagePickerController alloc] init];
imagePickerController.modalPresentationStyle = UIModalPresentationPopover; //this line is very important, because otherwise, the tab bar could go out of scope (a consequence of using modal segues and tab controllers!)
imagePickerController.sourceType = sourceType;
imagePickerController.delegate = self;
imagePickerController.allowsEditing = YES;
[self presentViewController:imagePickerController animated:YES completion:nil];
}