ipad 开启画中画的设备拍照闪退~

[xiaohange]

近期在bug后台收到一条NSInternalInconsistencyException导致闪退的记录。

出错堆栈如下：

-[AVCaptureStillImageOutput captureStillImageAsynchronouslyFromConnection:completionHandler:] Inconsistent state

同时注意到该错误全部发生在iPad上。

最后查到原因是在iPad上开启了画中画的情况下，使用AVCaptureSession拍照由于session处于被interrupt的状态，所以会导致闪退。还有其他的原因例如打电话，闹铃，处在分屏模式下等。

解决办法：在session startRunning前添加AVCaptureSessionWasInterrupted通知的观察。样例代码如下：

#pragma mark - Session Notifications

- (void) addObservers

{

    /*

    A session can only run when the app is full screen. It will be interrupted

    in a multi-app layout, introduced in iOS 9, see also the documentation of

    AVCaptureSessionInterruptionReason. Add observers to handle these session

    interruptions and show a preview is paused message. See the documentation

    of AVCaptureSessionWasInterruptedNotification for other interruption reasons.

    */

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sessionWasInterrupted:) name:AVCaptureSessionWasInterruptedNotification object:self.session];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sessionInterruptionEnded:) name:AVCaptureSessionInterruptionEndedNotification object:self.session];

}

- (void) removeObservers

{

    [[NSNotificationCenter defaultCenter] removeObserver:self];

}

- (void) sessionWasInterrupted:(NSNotification*)notification

{

    AVCaptureSessionInterruptionReason reason = [notification.userInfo[AVCaptureSessionInterruptionReasonKey] integerValue];

    NSLog(@"Capture session was interrupted with reason %ld", (long)reason);

    //在此禁止掉拍照功能，同时添加提醒

    if (reason == AVCaptureSessionInterruptionReasonAudioDeviceInUseByAnotherClient ||

        reason == AVCaptureSessionInterruptionReasonVideoDeviceInUseByAnotherClient) {

    }

    else if (reason == AVCaptureSessionInterruptionReasonVideoDeviceNotAvailableWithMultipleForegroundApps) {

    }

    else if (@available(iOS 11.1, *)) {

        if (reason == AVCaptureSessionInterruptionReasonVideoDeviceNotAvailableDueToSystemPressure) {

        }

    } else {

        // Fallback on earlier versions

    }

}

- (void) sessionInterruptionEnded:(NSNotification*)notification

{

  //在此可以恢复拍照功能

}