ios - タッチを検出しないinputAccessoryViewに追加されたUIButton

Question

をinputAccessoryView含む がありますUIButtonが、UIButtonはタップに応答しません (画像の変更すらありません)。理由はわかりません。これが私のかなり単純なコードです：

UIImageView *accessoryView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 60)];

UIButton *selectionModeOkButton = [[UIButton alloc] initWithFrame:CGRectMake(264, 11, 50, 46)];
[selectionModeOkButton setImage:[UIImage imageNamed:@"btn_count_ok_unpressed"] forState:UIControlStateNormal];
[selectionModeOkButton setImage:[UIImage imageNamed:@"btn_count_ok_pressed"] forState:UIControlStateHighlighted];
[selectionModeOkButton addTarget:self action:@selector(selectionModeOkButtonPressed) forControlEvents:UIControlEventTouchUpInside];
[accessoryView addSubview:selectionModeOkButton];

self.selectionModeTextField.inputAccessoryView = accessoryView;