介绍
从IOS5开始，IOS系统已经在siri上集成了语音合成的功能，但是是私有API。但是在IOS7，新增了一个简单的API----AVSpeechSynthesizer来做这件事情。嗓音IOS7包含了一组可以用来合成的声音的嗓音，你可以自定义多种嗓音来合成。 AVSpeechSynthesisVoice:speechVoices返回当前可用的嗓音数组：2013-07-12 10:49:26.929 GreetingSpeaker[31267:70b] ("[AVSpeechSynthesisVoice 0x978a0b0] Language: th-TH", "[AVSpeechSynthesisVoice 0x977a450] Language: pt-BR", "[AVSpeechSynthesisVoice 0x977a480] Language: sk-SK","[AVSpeechSynthesisVoice 0x978ad50] Language: fr-CA", "[AVSpeechSynthesisVoice 0x978ada0] Language: ro-RO", "[AVSpeechSynthesisVoice 0x97823f0] Language: no-NO","[AVSpeechSynthesisVoice 0x978e7b0] Language: fi-FI", "[AVSpeechSynthesisVoice 0x978af50] Language: pl-PL", "[AVSpeechSynthesisVoice 0x978afa0] Language: de-DE", "[AVSpeechSynthesisVoice 0x978e390] Language: nl-NL", "[AVSpeechSynthesisVoice 0x978b030] Language: id-ID", "[AVSpeechSynthesisVoice 0x978b080] Language: tr-TR", "[AVSpeechSynthesisVoice 0x978b0d0] Language: it-IT", "[AVSpeechSynthesisVoice 0x978b120] Language: pt-PT","[AVSpeechSynthesisVoice 0x978b170] Language: fr-FR","[AVSpeechSynthesisVoice 0x978b1c0] Language: ru-RU", "[AVSpeechSynthesisVoice 0x978b210]Language: es-MX", "[AVSpeechSynthesisVoice 0x978b2d0] Language: zh-HK","[AVSpeechSynthesisVoice 0x978b320] Language: sv-SE", "[AVSpeechSynthesisVoice 0x978b010] Language: hu-HU","[AVSpeechSynthesisVoice 0x978b440] Language: zh-TW","[AVSpeechSynthesisVoice 0x978b490] Language: es-ES","[AVSpeechSynthesisVoice 0x978b4e0] Language: zh-CN", "[AVSpeechSynthesisVoice 0x978b530] Language: nl-BE", "[AVSpeechSynthesisVoice 0x978b580] Language: en-GB","[AVSpeechSynthesisVoice 0x978b5d0] Language: ar-SA", "[AVSpeechSynthesisVoice 0x978b620] Language: ko-KR","[AVSpeechSynthesisVoice 0x978b670] Language: cs-CZ","[AVSpeechSynthesisVoice 0x978b6c0] Language: en-ZA", "[AVSpeechSynthesisVoice 0x978aed0] Language: en-AU","[AVSpeechSynthesisVoice 0x978af20] Language: da-DK","[AVSpeechSynthesisVoice 0x978b810] Language: en-US","[AVSpeechSynthesisVoice 0x978b860] Language: en-IE","[AVSpeechSynthesisVoice 0x978b8b0] Language: hi-IN", "[AVSpeechSynthesisVoice 0x978b900] Language: el-GR","[AVSpeechSynthesisVoice 0x978b950] Language: ja-JP" )用下面的方法来创建一个特殊的嗓音：AVSpeechSynthesisVoice *voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"en-US"];如果嗓音不能被识别，返回值为nil。话语话语代表一段讲话，可以传递到语音合成器来生成一段语音流。话语可以用待发音的字符串来创建：AVSpeechUtterance *utterance = [AVSpeechUtterance speechUtteranceWithString:@"Hello world!"];我们可以设置它的嗓音属性voice：utterence.voice = voice;还有其他各种属性，包括：rate，volume和pitchMultiplier。例如，稍微放慢语速：utterance.rate *= 0.7;当话语创建完成，可以把它放到语音合成器中。语音合成器会生成音频：AVSpeechSynthesizer *speechSynthesizer = [[AVSpeechSynthesizer alloc] init];[speechSynthesizer speakUtterance:utterance];话语会被合成器放到队列中，所以不用等待上一个结束，可以连续传送。但是，如果你尝试传送一个已经在队列中的话语，系统会抛出异常。实现本文的例子是一个关于多语言问候语的应用。这充分体现了语音合成的通用性。注意：定义话语的字符串都是罗马字符，例如中文的'Ni hao'。示例项目定义了一个类，可以生成一组嗓音对应的话语。项目有一个选择器供用户选择语言，然后按按钮可以听到对应的生成的语音。总结在IOS7，语音合成器非常简单，而且包含很多语言。合理的使用，可以提高应用的访问性，而不用时刻用你的手和眼来操作应用。