具有AVAudioSessionCategoryPlayAndRecord会话类别的蓝牙输出不起作用

Question

任何人都知道为什么我无法在AVAudioSessionCategoryPlayAndRecord类别的iPad（iOS 5）上使用蓝牙输出。

下面是我用来设置AVAudioSessionCategoryPlayAndRecord类别并启用蓝牙的代码。如果我将类别切换到AVAudioSessionCategoryPlayback，蓝牙输出可以很好地适用于各种耳机和耳机。一旦我切换到PlayAndRecord，就没有蓝牙输出。

我做错了什么？

建议，假设赞赏。感谢。

- (BOOL) setAudioSessionCategoryToPlayAndRecordWithBluetoothEnabled {
    AudioSessionInitialize(NULL,NULL,NULL,NULL);

    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    NSError *err;

    if (![audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&err])
    {
        fprintf(stderr,"oh no...");
        return NO;
    }

        // make active
    [audioSession setActive: YES error: nil];

        // allow bluetooth
    UInt32 allowBluetoothInput = 1;
    OSStatus stat =  AudioSessionSetProperty (
                                              kAudioSessionProperty_OverrideCategoryEnableBluetoothInput,
                                              sizeof (allowBluetoothInput),
                                              &allowBluetoothInput
                                              );

    if (stat) {
        fprintf(stderr,"not good...");
        return FALSE;
    }


        // check for bluetooth route 
        // (NB: this never works if category is AVAudioSessionCategoryPlayAndRecord)
    UInt32 size = sizeof(CFStringRef);
    CFStringRef route;
    stat = AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &size, &route);
    NSLog(@"route = %@", route);    


    return TRUE;

}