解决ios下使用uiwebview载入网页时，插放网页中视频或者音频无声音解决办法

<pre name="code" class="objc">- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
   
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    BOOL ok;
    NSError *setCategoryError = nil;
    ok = [audioSession setCategory:AVAudioSessionCategoryPlayback        error:&setCategoryError];
    if (!ok) {
        NSLog(@"%s setCategoryError=%@", __PRETTY_FUNCTION__, setCategoryError);
    }
……...

其它需求，可以读 iOS Human Interface Guidelines这章