手把手教你uinput命令的使用方式-重学安卓input子系统

背景：

android系统中自带了一个uinput命令，但是这个命令其实对于使用者并不友好，因为本身命令的使用没有相关的help提示，命令的使用方式基本上整个互联网上都没有相关的文章。
所以本文要带大家学习一下如何使用uinput命令实现input事件的注入。

uinput命令使用的帮助部分

uinput的命令，因为网络找不到资料，我们属于互联网知识开荒一样，如何使用其实主要看如下文件：
frameworks/base/cmds/uinput/README.md

There are two ways to use the `uinput` command:

* **Recommended:** `uinput -` reads commands from standard input until End-of-File (Ctrl+D) is sent.
  This mode can be used interactively from a terminal or used to control uinput from another program
  or app (such as the CTS tests via [`UinputDevice`][UinputDevice]).
* `uinput <filename>` reads commands from a file instead of standard input.

There are also two supported input formats, described in the sections below. The tool will
automatically detect which format is being used.

也就是这里一共两个方式来使用uinput命令
1、“uinput -” 这种方式主要是获取输入是从标准输入流获取数据

2、“uinput “也就是最简单的，uinput命令后面直接加文件的路径名字

其实本质上两个命令方式没有本质区别，都是要一个文件作为输入。
那么请问这个文件到底长什么样子呢？

这里其实是可以也可以通过上面帮助文档看到蛛丝马迹

There are also two supported input formats, described in the sections below. The tool will
automatically detect which format is being used.

[UinputDevice]: https://cs.android.com/android/platform/superproject/main/+/main:cts/libs/input/src/com/android/cts/input/UinputDevice.java

## evemu recording format (recommended)

`uinput` supports the evemu format, as used by the [FreeDesktop project's evemu suite][FreeDesktop].
This is a simple text-based format compatible with recording and replay tools on other platforms.
However, it only supports playback of events from one device from a single recording. Recordings can
be made using the `evemu-record` command on Android or other Linux-based OSes.

[FreeDesktop]: https://gitlab.freedesktop.org/libevdev/evemu

## JSON-like format

The other supported format is JSON-based, though the parser is in [lenient mode] to allow comments,
and integers can be specified in hexadecimal (e.g. `0xABCD`). The input file (or standard input) can
contain multiple commands, which will be executed in sequence. Simply add multiple JSON objects to
the file, one after the other without separators:

依赖文件主要有两种格式：
一种是官方推荐的evemu recording format格式，也是本文重点讲解格式
另一种是JSON-like format，这里因为官方不推荐，所以暂时不进行介绍

那么来看看evemu recording format来自哪里呢？这里也需要看看帮助文档

`uinput` supports the evemu format, as used by the [FreeDesktop project's evemu suite][FreeDesktop].
This is a simple text-based format compatible with recording and replay tools on other platforms.
However, it only supports playback of events from one device from a single recording. Recordings can
be made using the `evemu-record` command on Android or other Linux-based OSes.

[FreeDesktop]: https://gitlab.freedesktop.org/libevdev/evemu

上面文档说明出来了，其实这个文件是可以通过evemu-record命令进行录制的，这里大家肯定有疑问evemu-record是啥，他的代码在哪，如何进行使用？
下面重点看看evemu-record相关

evemu-record相关代码及使用

代码路径：
frameworks/native/cmds/evemu-record

可以看看它的帮助文档
frameworks/native/cmds/evemu-record/README.md

# `evemu-record`

This is a Rust implementation of the `evemu-record` command from the [FreeDesktop project's evemu
suite][FreeDesktop]. It records the descriptor and events produced by a single input device in a
[simple text-based format][format] that can be replayed using the [`uinput` command on
Android][uinput] or the FreeDesktop evemu tools on other Linux-based platforms. It is included by
default with `userdebug` and `eng` builds of Android.

The command-line interface is the same as that of the FreeDesktop version, except for
Android-specific features. For usage instructions, run `evemu-record --help`.

上面可以看出evemu-record主要是用来记录录制设备上的event的相关输入事件，不过这里设备只支持单设备，而且只有在 userdebug and eng才会集成这个命令。
那么如何使用evemu-record生成对应格式文件呢？

录制部分

$ adb shell evemu-record > my-recording.evemu
Available devices:
/dev/input/event0:      gpio_keys
/dev/input/event1:      s2mpg12-power-keys
/dev/input/event2:      NVTCapacitiveTouchScreen
/dev/input/event3:      NVTCapacitivePen
/dev/input/event4:      uinput-folio
/dev/input/event5:      ACME Touchpad
Select the device event number [0-5]: 5

大家注意要手动输入event的序号，比如要录制是/dev/input/event5这个输入设备，那么就输入5.
输入后，在设备上进行相关的操作触发/dev/input/event5会有对应的事件，其实这个和触摸机器人是一样的，就是会全程记录某个输入的事件，只不过格式有所差别这里的格式是evemu recording format。
可以看看 my-recording.evemu文件格式如下：

uinput使用evemu文件进行事件注入

看看evemu的帮助

...then use the input device for a while, and press Ctrl+C to finish. You will now have a
`my-recording.evemu` file that you can examine in a text editor. To replay it, use the [`uinput`
command][uinput]:

$ adb shell uinput - < my-recording.evemu

上面步骤录制了my-recording.evemu文件后，现在就可以使用uinput来进行播放

用以下命令就可以

$ adb shell uinput - < my-recording.evemu

最后看看效果：

总结：
要使用uinput命令一共需要2个步骤：
1、录制好相关的 evemu-record文件，这里需要使用

 adb shell evemu-record > my-recording.evemu

2、使用录制好的my-recording.evemu

$ adb shell uinput - < my-recording.evemu