CameraX实现相机功能

预计实现功能：

实时预览（缩放、点击聚焦）
拍照（晃动拍照）、录像
实现左右滑动，切换拍照、录像
给拍照的图片加水印

CameraX是什么，能解决什么问题

Jetpack的一个支持库，最低版本要求Android5.0
默认的相机功能还是Camera2的能力，当然API都变了，同时提供CameraX Extensions拓展库可以添加各种特效，例如人像、HDR、夜间和美颜模式(从上图也可以看出，这是依赖OEM的)
绑定生命周期，所以Camera本身无需在生命周期中调用什么onPause onResume之类的样板代码，且忘记后会造成各种问题
抹平设备兼容性问题，无需在代码库中添加设备专属代码

准备工作

1. 注意事项

最低支持API是21
Android Studio 至少是3.6版本
Java8环境

2.导入依赖

dependencies {
  // CameraX core library using the camera2 implementation
  def camerax_version = "1.3.0-alpha06"
  // The following line is optional, as the core library is included indirectly by camera-camera2
  implementation "androidx.camera:camera-core:${camerax_version}"
  implementation "androidx.camera:camera-camera2:${camerax_version}"
  // If you want to additionally use the CameraX Lifecycle library
  implementation "androidx.camera:camera-lifecycle:${camerax_version}"
  // If you want to additionally use the CameraX VideoCapture library
  implementation "androidx.camera:camera-video:${camerax_version}"
  // If you want to additionally use the CameraX View class
  implementation "androidx.camera:camera-view:${camerax_version}"
  // If you want to additionally add CameraX ML Kit Vision Integration
  implementation "androidx.camera:camera-mlkit-vision:${camerax_version}"
  // If you want to additionally use the CameraX Extensions library
  implementation "androidx.camera:camera-extensions:${camerax_version}"
}