为什么AppDelegate中的AVPlayer类引用返回nil

Question

我正在尝试处理音频流中断，当用户接到呼叫时，音频会暂停，然后在呼叫结束时应该会恢复。

但是，在下面显示的代码[myAVPlayer pauseAACStreaming:self];和[myAVPlayer playACCStreaming:self];中，我对MyAVPlayer类的引用返回nil。

既然我有音频播放，为什么是nil？有更好的方法吗？

我在AppDelegate.h中引用了一个自定义类MyAVPlayer，如下所示：

@class MyAVPlayer;
@interface AppDelegate : NSObject <UIApplicationDelegate> 
{
   MyAVPlayer *myAVPlayer;
} 
@property (nonatomic, retain)  MyAVPlayer *myAVPlayer;

然后，在AppDelegate.m中，我有：

#import "MyAVPlayer.h"
void AudioSessionInterruptionListenerCallBack(void *inClientData, UInt32 inInterruptionState);
@implementation AppDelegate
@synthesize myAVPlayer;
void AudioSessionInterruptionListenerCallBack (void *inClientData, UInt32 inInterruptionState)
{
    NSLog(@"Audio session interruption");
    MyAVPlayer* streamer = (MyAVPlayer *)inClientData;
    [streamer handleInterruptionChangeToState:inInterruptionState];
}
- (void)applicationWillResignActive:(UIApplication *)application
{
    AudioSessionInitialize (
                            NULL,                         
                            NULL,                          
                            AudioSessionInterruptionListenerCallBack,  
                            self                       
                            );
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    AudioSessionInitialize (
                            NULL,                         
                            NULL,                          
                            AudioSessionInterruptionListenerCallBack,  
                            self                       
                            );
}

- (void)handleInterruptionChangeToState:(AudioQueuePropertyID)inInterruptionState 
{
     NSLog(@"handleInterruptionChangeToState");
    if (inInterruptionState == kAudioSessionBeginInterruption)
    { 
        [myAVPlayer pauseAACStreaming:self];  
    }
    else if (inInterruptionState == kAudioSessionEndInterruption) 
    {
        AudioSessionSetActive( true );
               [myAVPlayer playACCStreaming:self];      
    }
}

Answer 1

这是因为您实际上没有将实例变量分配给任何东西！

Answer 2

问题是您有一个名为myAVPlayer的属性，但您使用以下行分配的变量：

MyAVPlayer* streamer = (MyAVPlayer *)inClientData;

相反，您应该使用：

self.myAVPlayer = (MyAVPlayer *)inClientData;