January 2020
Intermediate to advanced
356 pages
6h 4m
Chinese
Content preview from Swift游戏开发经典实例
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声音
｜
137
不要用同一个
AVSpeechUtterance
调用
speakUtterance
方法两次，这会导
致一个错误，
App
会立即崩溃。
在合成器开始朗诵后，我们可以让它暂停。暂停可以是立即暂停，也可以是在下一
个单词暂停：
//
立即暂停发声
self.speechSynthesizer.pauseSpeaking (at: AVSpeechBoundary.Immediate)
//
在当前单词念完之后暂停
self.speechSynthesizer.pauseSpeaking (at: AVSpeechBoundary.Word)
暂停后随时可以继续朗诵：
self.speechSynthesizer.continueSpeaking()
朗诵完毕，我们可以用
stopSpeaking(at:)
方法清空
AVSpeechSynthesizer
并添
加新的
AVSpeechUtterance
。这个方法和
pauseSpeaking(at:)
差不多，只不过
stopSpeaking(at:)
会让
AVSpeechSynthesizer
把所有说过的
AVSpeechUtterance
清除。
4.6
获知音乐程序当前播放曲目
问题
如何知道系统音乐程序正在播放哪首歌曲？
解决方案
这个问题需要用到
Media Player
框架。首先在你的代码中引入
MediaPlayer
模块。
首先从系统获得一个
MPMusicPlayerController
对象，这个对象包含了内置音乐库
的信息。接着，获得当前正在播放的
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.