February 2017
Beginner to intermediate
472 pages
9h 53m
Chinese
Content preview from Swift学习手册
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350
｜
第
14
章
可惜，模拟器不允许录音，因为它没有真正的录音硬件。然而，模拟器可以播放在
其他设备中录制的音频。
现在可以添加和播放音频附件了。
14.3
视频附件
iOS
拥有丰富的摄像功能，下面将为这个应用添加录像功能。与本章实现的前两
个附件类型不同，我们无需自己实现视图控制器，使用
iOS
提供的视图控制器即
可。我们将使用
UIImagePickerController
（在第
11
章首次见到）录像，使用
AVPlayerViewController
视图控制器播放视频。
1.
首先，添加表示这种附件类型的图标。打开
Assets.xcassets
，添加
Video
图标。
2.
然后，修改
Document
类，返回视频的图像。打开
Document.swift
，把下述代码添加
到
NSFileWrapper
扩展的
thumbnailImage
方法中：
func thumbnailImage() -> UIImage? {
if self.conformsToType(kUTTypeImage) {
//
如果是图像，作为
UIImage
对象返回
//
确保可以访问文件的内容
guard let attachmentContent = self.regularFileContents else {
return nil
}
//
尝试把文件的内容转换成文本
return UIImage(data: attachmentContent)
}
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