ios6中文键盘按右上角锁屏后crash解决办法

- (void)applicationDidEnterBackground:(UIApplication *)application{    // Acquired additional time    UIDevice *device = [UIDevice currentDevice];    BOOL backgroundSupported = NO;    if ([device respondsToSelector:@selector(isMultitaskingSupported)]) {        backgroundSupported = device.multitaskingSupported;    }    if (backgroundSupported) {        backgroundTask = [application beginBackgroundTaskWithExpirationHandler:^{            [application endBackgroundTask:backgroundTask];            backgroundTask = UIBackgroundTaskInvalid;        }];    }    // Hide keyboard     [self.textField resignFirstResponder];}

http://stackoverflow.com/questions/12730660/application-crash-on-lock-when-japanese-keyboard-used