iOS开发之多媒体播放

   

iOS sdk中提供了很多方便的方法来播放多媒体。本文将利用这些SDK做一个demo，来讲述一下如何使用它们来播放音频文件。

AudioToolbox framework

使用AudioToolbox framework。这个框架可以将比较短的声音注册到 system sound服务上。被注册到system sound服务上的声音称之为 system sounds。它必须满足下面几个条件。

1、播放的时间不能超过30秒

2、数据必须是 PCM或者IMA4流格式

3、必须被打包成下面三个格式之一：Core Audio Format (.caf), Waveform audio (.wav),或者 Audio Interchange File (.aiff)

声音文件必须放到设备的本地文件夹下面。通过AudioServicesCreateSystemSoundID方法注册这个声音文件，AudioServicesCreateSystemSoundID需要声音文件的url的CFURLRef对象。看下面注册代码：

<div class="cnblogs_code"><pre><span style="color: #0000ff;">#import</span><span style="color: #000000;"> </span><span style="color: #000000;"><</span><span style="color: #000000;">AudioToolbox</span><span style="color: #000000;">/</span><span style="color: #000000;">AudioToolbox.h</span><span style="color: #000000;">></span><span style="color: #000000;">
</span><span style="color: #0000ff;">@interface</span><span style="color: #000000;"> MediaPlayerViewController : UIViewController
{
    IBOutlet UIButton </span><span style="color: #000000;">*</span><span style="color: #000000;">audioButton;
    SystemSoundID shortSound;
}</span></pre>
<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">id</span><span style="color: #000000;">)init
{
    self </span><span style="color: #000000;">=</span><span style="color: #000000;"> [super initWithNibName:</span><span style="color: #800000;">@"</span><span style="color: #800000;">MediaPlayerViewController</span><span style="color: #800000;">"</span><span style="color: #000000;"> bundle:nil];
    </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (self) {
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> Get the full path of Sound12.aif</span><span style="color: #008000;">
</span><span style="color: #000000;">        NSString </span><span style="color: #000000;">*</span><span style="color: #000000;">soundPath </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[NSBundle mainBundle] pathForResource:</span><span style="color: #800000;">@"</span><span style="color: #800000;">Sound12</span><span style="color: #800000;">"</span><span style="color: #000000;">
                                                              ofType:</span><span style="color: #800000;">@"</span><span style="color: #800000;">aif</span><span style="color: #800000;">"</span><span style="color: #000000;">];
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> If this file is actually in the bundle...</span><span style="color: #008000;">
</span><span style="color: #000000;">        </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (soundPath) {
            </span><span style="color: #008000;">//</span><span style="color: #008000;"> Create a file URL with this path</span><span style="color: #008000;">
</span><span style="color: #000000;">            NSURL </span><span style="color: #000000;">*</span><span style="color: #000000;">soundURL </span><span style="color: #000000;">=</span><span style="color: #000000;"> [NSURL fileURLWithPath:soundPath];
       
            </span><span style="color: #008000;">//</span><span style="color: #008000;"> Register sound file located at that URL as a system sound</span><span style="color: #008000;">
</span><span style="color: #000000;">            OSStatus err </span><span style="color: #000000;">=</span><span style="color: #000000;"> AudioServicesCreateSystemSoundID((CFURLRef)soundURL,
                                                            </span><span style="color: #000000;">&amp;</span><span style="color: #000000;">shortSound);
            </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (err </span><span style="color: #000000;">!=</span><span style="color: #000000;"> kAudioServicesNoError)
                NSLog(</span><span style="color: #800000;">@"</span><span style="color: #800000;">Could not load %@, error code: %d</span><span style="color: #800000;">"</span><span style="color: #000000;">, soundURL, err);
        }
    }
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> self;
}</span></pre>
这样就可以使用下面代码播放声音了：

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (IBAction)playShortSound:(</span><span style="color: #0000ff;">id</span><span style="color: #000000;">)sender
{
    AudioServicesPlaySystemSound(shortSound);
}</span></pre>
使用下面代码，还加一个震动的效果：

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (IBAction)playShortSound:(</span><span style="color: #0000ff;">id</span><span style="color: #000000;">)sender
{
    AudioServicesPlaySystemSound(shortSound);
    AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
}</span></pre>
AVFoundation framework

对于压缩过Audio文件，或者超过30秒的音频文件，可以使用AVAudioPlayer类。这个类定义在AVFoundation framework中。

下面我们使用这个类播放一个mp3的音频文件。首先要引入AVFoundation framework，然后MediaPlayerViewController.h中添加下面代码：

<div class="cnblogs_code"><pre><span style="color: #0000ff;">#import</span><span style="color: #000000;"> </span><span style="color: #000000;"><</span><span style="color: #000000;">AVFoundation</span><span style="color: #000000;">/</span><span style="color: #000000;">AVFoundation.h</span><span style="color: #000000;">></span><span style="color: #000000;">
</span><span style="color: #0000ff;">@interface</span><span style="color: #000000;"> MediaPlayerViewController : UIViewController </span><span style="color: #000000;"><</span><span style="color: #000000;">AVAudioPlayerDelegate</span><span style="color: #000000;">></span><span style="color: #000000;">
{
    IBOutlet UIButton </span><span style="color: #000000;">*</span><span style="color: #000000;">audioButton;
    SystemSoundID shortSound;
    AVAudioPlayer </span><span style="color: #000000;">*</span><span style="color: #000000;">audioPlayer;</span></pre>
AVAudioPlayer类也是需要知道音频文件的路径，使用下面代码创建一个AVAudioPlayer实例：

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">id</span><span style="color: #000000;">)init
{
    self </span><span style="color: #000000;">=</span><span style="color: #000000;"> [super initWithNibName:</span><span style="color: #800000;">@"</span><span style="color: #800000;">MediaPlayerViewController</span><span style="color: #800000;">"</span><span style="color: #000000;"> bundle:nil];
   
    </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (self) {
   
        NSString </span><span style="color: #000000;">*</span><span style="color: #000000;">musicPath </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[NSBundle mainBundle] pathForResource:</span><span style="color: #800000;">@"</span><span style="color: #800000;">Music</span><span style="color: #800000;">"</span><span style="color: #000000;">
                                                              ofType:</span><span style="color: #800000;">@"</span><span style="color: #800000;">mp3</span><span style="color: #800000;">"</span><span style="color: #000000;">];
        </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (musicPath) {
            NSURL </span><span style="color: #000000;">*</span><span style="color: #000000;">musicURL </span><span style="color: #000000;">=</span><span style="color: #000000;"> [NSURL fileURLWithPath:musicPath];
            audioPlayer </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL
                                                                 error:nil];
            [audioPlayer setDelegate:self];
        }
        NSString </span><span style="color: #000000;">*</span><span style="color: #000000;">soundPath </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[NSBundle mainBundle] pathForResource:</span><span style="color: #800000;">@"</span><span style="color: #800000;">Sound12</span><span style="color: #800000;">"</span><span style="color: #000000;">
                                                              ofType:</span><span style="color: #800000;">@"</span><span style="color: #800000;">aif</span><span style="color: #800000;">"</span><span style="color: #000000;">];</span></pre>
我们可以在一个button的点击事件中开始播放这个mp3文件，如：

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (IBAction)playAudioFile:(</span><span style="color: #0000ff;">id</span><span style="color: #000000;">)sender
{
    </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> ([audioPlayer isPlaying]) {
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> Stop playing audio and change text of button</span><span style="color: #008000;">
</span><span style="color: #000000;">        [audioPlayer stop];
        [sender setTitle:</span><span style="color: #800000;">@"</span><span style="color: #800000;">Play Audio File</span><span style="color: #800000;">"</span><span style="color: #000000;">
                forState:UIControlStateNormal];
    }
    </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> {
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> Start playing audio and change text of button so
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> user can tap to stop playback</span><span style="color: #008000;">
</span><span style="color: #000000;">        [audioPlayer play];
        [sender setTitle:</span><span style="color: #800000;">@"</span><span style="color: #800000;">Stop Audio File</span><span style="color: #800000;">"</span><span style="color: #000000;">
                forState:UIControlStateNormal];
    }
}</span></pre>
这样运行我们的程序，就可以播放音乐了。

这个类对应的<span style="color: #000000;"><span style="font-family: Courier New;">AVAudioPlayerDelegate</span></span>有两个委托方法。一个是 audioPlayerDidFinishPlaying:successfully: 当音频播放完成之后触发。当播放完成之后，可以将播放按钮的文本重新回设置成：Play Audio File

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">void</span><span style="color: #000000;">)audioPlayerDidFinishPlaying:(AVAudioPlayer </span><span style="color: #000000;">*</span><span style="color: #000000;">)player
                       successfully:(BOOL)flag
{
    [audioButton setTitle:</span><span style="color: #800000;">@"</span><span style="color: #800000;">Play Audio File</span><span style="color: #800000;">"</span><span style="color: #000000;">
                 forState:UIControlStateNormal];
}</span></pre>
另一个是audioPlayerEndInterruption:，当程序被应用外部打断之后，重新回到应用程序的时候触发。在这里当回到此应用程序的时候，继续播放音乐。

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">void</span><span style="color: #000000;">)audioPlayerEndInterruption:(AVAudioPlayer </span><span style="color: #000000;">*</span><span style="color: #000000;">)player
{
    [audioPlayer play];
}</span></pre>
MediaPlayer framework

播放电影文件：

iOS sdk中可以使用MPMoviePlayerController来播放电影文件。但是在iOS设备上播放电影文件有严格的格式要求，只能播放下面两个格式的电影文件。

? H.264 (Baseline Profile Level 3.0)<br>? MPEG-4 Part 2 video (Simple Profile)

幸运的是你可以先使用iTunes将文件转换成上面两个格式。<br>MPMoviePlayerController还可以播放互联网上的视频文件。但是建议你先将视频文件下载到本地，然后播放。如果你不这样做，iOS可能会拒绝播放很大的视频文件。

这个类定义在MediaPlayer framework中。在你的应用程序中，先添加这个引用，然后修改<span style="font-family: Courier New;">MediaPlayerViewController.</span>h文件。

<div class="cnblogs_code"><pre><span style="color: #0000ff;">#import</span><span style="color: #000000;"> </span><span style="color: #000000;"><</span><span style="color: #000000;">MediaPlayer</span><span style="color: #000000;">/</span><span style="color: #000000;">MediaPlayer.h</span><span style="color: #000000;">></span><span style="color: #000000;">
</span><span style="color: #0000ff;">@interface</span><span style="color: #000000;"> MediaPlayerViewController : UIViewController </span><span style="color: #000000;"><</span><span style="color: #000000;">AVAudioPlayerDelegate</span><span style="color: #000000;">></span><span style="color: #000000;">
{
    MPMoviePlayerController </span><span style="color: #000000;">*</span><span style="color: #000000;">moviePlayer;</span></pre>
下面我们使用这个类来播放一个.m4v 格式的视频文件。与前面的类似，需要一个url路径。

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">id</span><span style="color: #000000;">)init
{
    self </span><span style="color: #000000;">=</span><span style="color: #000000;"> [super initWithNibName:</span><span style="color: #800000;">@"</span><span style="color: #800000;">MediaPlayerViewController</span><span style="color: #800000;">"</span><span style="color: #000000;"> bundle:nil];
    </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (self) {
   
        NSString </span><span style="color: #000000;">*</span><span style="color: #000000;">moviePath </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[NSBundle mainBundle] pathForResource:</span><span style="color: #800000;">@"</span><span style="color: #800000;">Layers</span><span style="color: #800000;">"</span><span style="color: #000000;">
                                                              ofType:</span><span style="color: #800000;">@"</span><span style="color: #800000;">m4v</span><span style="color: #800000;">"</span><span style="color: #000000;">];
        </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (moviePath) {
            NSURL </span><span style="color: #000000;">*</span><span style="color: #000000;">movieURL </span><span style="color: #000000;">=</span><span style="color: #000000;"> [NSURL fileURLWithPath:moviePath];
            moviePlayer </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[MPMoviePlayerController alloc]
                                    initWithContentURL:movieURL];
        }</span></pre>
MPMoviePlayerController有一个视图来展示播放器控件，我们在viewDidLoad方法中，将这个播放器展示出来。

<div class="cnblogs_code"><pre><span style="color: #000000;">-</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">void</span><span style="color: #000000;">)viewDidLoad
{
    [[self view] addSubview:[moviePlayer view]];
    </span><span style="color: #0000ff;">float</span><span style="color: #000000;"> halfHeight </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[self view] bounds].size.height </span><span style="color: #000000;">/</span><span style="color: #000000;"> </span><span style="color: #800080;">2.0</span><span style="color: #000000;">;
    </span><span style="color: #0000ff;">float</span><span style="color: #000000;"> width </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[self view] bounds].size.width;
    [[moviePlayer view] setFrame:CGRectMake(</span><span style="color: #800080;">0</span><span style="color: #000000;">, halfHeight, width, halfHeight)];
}</span></pre>
还有一个MPMoviePlayerViewController类，用于全屏播放视频文件，用法和MPMoviePlayerController一样。

<div class="cnblogs_code"><pre><span style="color: #000000;">MPMoviePlayerViewController </span><span style="color: #000000;">*</span><span style="color: #000000;">playerViewController </span><span style="color: #000000;">=</span><span style="color: #000000;">
    [[MPMoviePlayerViewController alloc] initWithContentURL:movieURL];
  [viewController presentMoviePlayerViewControllerAnimated:playerViewController];</span></pre>
我们在听音乐的时候，可以用iphone做其他的事情，这个时候需要播放器在后台也能运行，我们只需要在应用程序中做个简单的设置就行了。

1、在Info property list中加一个 Required background modes节点，它是一个数组，将第一项设置成设置App plays audio。

2、在播放mp3的代码中加入下面代码：

<div class="cnblogs_code"><pre><span style="color: #000000;">    </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (musicPath) {
        NSURL </span><span style="color: #000000;">*</span><span style="color: #000000;">musicURL </span><span style="color: #000000;">=</span><span style="color: #000000;"> [NSURL fileURLWithPath:musicPath];
        [[AVAudioSession sharedInstance]
                    setCategory:AVAudioSessionCategoryPlayback error:nil];
        audioPlayer </span><span style="color: #000000;">=</span><span style="color: #000000;"> [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL
                                                             error:nil];
        [audioPlayer setDelegate:self];
    }</span></pre>
在后台运行的播放音乐的功能在模拟器中看不出来，只有在真机上看效果。

<img alt="" src="http://hi.csdn.net/attachment/201107/24/0_1311506457iPg4.gif">

总结：本文通过例子详细讲解了iOS sdk中用于播放音频文件的类，文章后面有本文的代码提供下载。

代码：点击打开链接