最近将 appium 更新到了 1.6.5，uiautomator2 确实能实现对 Android toast 内容的断言。但后续发现之前的wd.pressDeviceKey()方法不起作用。

更新

wd@1.3.0添加了 press_keycode 的路由，修复了这个 bug
Replace the deprecated sendKeyEvent API with pressKeycode for Appium

POST /session/:sessionId/appium/device/press_keycode
Send key event to device (mjsonWire).

pressKeycode(keycode, metastate, cb) -> cb(err)
metastate is optional.

问题

首先分析 appium server 的日志:

2017-07-04 10:10:14:838 - info: [HTTP] --> POST /wd/hub/session/744e508b-3f7c-446b-b75f-a4373b0da0c1/appium/device/keyevent {"keycode":4}
2017-07-04 10:10:14:838 - info: [MJSONWP] Driver proxy active, passing request on via HTTP proxy
2017-07-04 10:10:14:838 - info: [debug] [JSONWP Proxy] Proxying [POST /wd/hub/session/744e508b-3f7c-446b-b75f-a4373b0da0c1/appium/device/keyevent] to [POST http://localhost:8200/wd/hub/session/3705f215-26ac-409d-a89d-c9ab578af2b4/appium/device/keyevent] with body: {"keycode":4}
2017-07-04 10:10:14:947 - error: [MJSONWP] Encountered internal error running command: Error: Could not proxy. Proxy error: Could not proxy command to remote server. Original error: 404 - undefined
    at doJwpProxy$ (C:\Users\lichen2\AppData\Local\Programs\appium-desktop\resources\app\node_modules\appium\node_modules\appium-base-driver\lib\mjsonwp\mjsonwp.js:354:13)
    at tryCatch (C:\Users\lichen2\AppData\Local\Programs\appium-desktop\resources\app\node_modules\appium\node_modules\babel-runtime\regenerator\runtime.js:67:40)
    at GeneratorFunctionPrototype.invoke [as _invoke] (C:\Users\lichen2\AppData\Local\Programs\appium-desktop\resources\app\node_modules\appium\node_modules\babel-runtime\regenerator\runtime.js:315:22)
    at GeneratorFunctionPrototype.prototype.(anonymous function) [as throw] (C:\Users\lichen2\AppData\Local\Programs\appium-desktop\resources\app\node_modules\appium\node_modules\babel-runtime\regenerator\runtime.js:100:21)
    at GeneratorFunctionPrototype.invoke (C:\Users\lichen2\AppData\Local\Programs\appium-desktop\resources\app\node_modules\appium\node_modules\babel-runtime\regenerator\runtime.js:136:37)
2017-07-04 10:10:14:947 - info: [HTTP] <-- POST /wd/hub/session/744e508b-3f7c-446b-b75f-a4373b0da0c1/appium/device/keyevent 500 119 ms - 274 

日志显示，Appium server 接收到了keyevent的 POST 请求，但转发出去时： Error: Could not proxy. Proxy error: Could not proxy command to remote server. Original error: 404 - undefined，很明显，404 表示设备端的 sever 没有响应该请求。

原因

出了问题，第一反应是去 appium 上翻 Issue，确实有人提过同样的问题，但作者并没有给出 Answer：
Can't use sendKeyEvent。
于是只能自己翻源码了，因为问题出在 appium server 发 POST 到 uiautomator2 server 时 404，所以直接去appium-uiautomator2-server项目里看：
找到文件AppiumServelt，该类看上去是注册路由的：

private void registerPostHandler() {
        register(postHandler, new NewSession("/wd/hub/session"));
        register(postHandler, new FindElement("/wd/hub/session/:sessionId/element"));
        register(postHandler, new FindElements("/wd/hub/session/:sessionId/elements"));
        register(postHandler, new Click("/wd/hub/session/:sessionId/element/:id/click"));
        register(postHandler, new Click("/wd/hub/session/:sessionId/appium/tap"));
        register(postHandler, new Clear("/wd/hub/session/:sessionId/element/:id/clear"));
        register(postHandler, new RotateScreen("/wd/hub/session/:sessionId/orientation"));
        register(postHandler, new RotateScreen("/wd/hub/session/:sessionId/rotation"));
        register(postHandler, new PressBack("/wd/hub/session/:sessionId/back"));
        register(postHandler, new SendKeysToElement("/wd/hub/session/:sessionId/element/:id/value"));
        register(postHandler, new SendKeysToElement("/wd/hub/session/:sessionId/keys"));
        register(postHandler, new Swipe("/wd/hub/session/:sessionId/touch/perform"));
        register(postHandler, new TouchLongClick("/wd/hub/session/:sessionId/touch/longclick"));
        register(postHandler, new OpenNotification("/wd/hub/session/:sessionId/appium/device/open_notifications"));
        register(postHandler, new PressKeyCode("/wd/hub/session/:sessionId/appium/device/press_keycode"));
        register(postHandler, new LongPressKeyCode("/wd/hub/session/:sessionId/appium/device/long_press_keycode"));
        register(postHandler, new Drag("/wd/hub/session/:sessionId/touch/drag"));
        register(postHandler, new AppStrings("/wd/hub/session/:sessionId/appium/app/strings"));
        register(postHandler, new Flick("/wd/hub/session/:sessionId/touch/flick"));
        register(postHandler, new ScrollTo("/wd/hub/session/:sessionId/touch/scroll"));
        register(postHandler, new MultiPointerGesture("/wd/hub/session/:sessionId/touch/multi/perform"));
        register(postHandler, new TouchDown("/wd/hub/session/:sessionId/touch/down"));
        register(postHandler, new TouchUp("/wd/hub/session/:sessionId/touch/up"));
        register(postHandler, new TouchMove("/wd/hub/session/:sessionId/touch/move"));
        register(postHandler, new UpdateSettings("/wd/hub/session/:sessionId/appium/settings"));
        register(postHandler, new NetworkConnection("/wd/hub/session/:sessionId/network_connection"));
    }

发现上面代码里并没有对应 wd: POST /session/:sessionId/appium/device/keyevent，只有register(postHandler, new PressKeyCode("/wd/hub/session/:sessionId/appium/device/press_keycode"));
所以，404 的原因找到了，笔者也在上面的 Issue 里给作者提了，希望后面作者能更新下 uiautomator2 server。

解决

知道了问题原因，可以想到三种解决方案：

1.修改 uiautomator2 server
对 appium 编译安装 uiautomator2 server 的过程没深入研究，尝试卸载原手机里的 io.appium.uiautomator2.server 程序，修改 AppiumServlet，并没有起作用，所以这个解决方法我还是等作者吧。。

更新
感谢 Carl 的提示，原来appium-uiautomator2-server项目的 Readme 已经给出编译方法。

• AS 打开 appium-uiautomator2-server 项目，完成上面提到的 AppiumServelt 代码的修改
• 运行gradle clean assembleServerDebug assembleServerDebugAndroidTest，这里编译可能会遇到一些问题，我遇到的是：app 的 build.gradle 中，配置了对 sdk-manager-plugin 的依赖，而阿里云的 maven 库里并没有收录这个项目。解决方法： 将相关配置的代码注释掉
• gradle 编译成功后，会在/app/build/outputs/apk/下生产两个 apk： 1.appium-uiautomator2-server-v0.1.5.APK，执行命令的 apk，（GitHub 上已经更新到 0.1.6） 2.appium-uiautomator2-server-debug-androidTest.apk，用于启动 Server 的 apk
• 替换设备中的 apk，可以手动安装，也可以替换 appium 下默认的 apk。默认 apk 放在 appium-uiautomator2-driver 的uiautomator2目录下，替换之。还未结束，查看 driver 里的uiautomator2.js代码：

async installServerApk () {
    // Installs the apks on to the device or emulator
    let apkPackage = await this.getPackageName(apkPath);
    // appending .test to apkPackage name to get test apk package name
    let testApkPackage = apkPackage + '.test';
    let isApkInstalled = await this.adb.isAppInstalled(apkPackage);
    let isTestApkInstalled = await this.adb.isAppInstalled(testApkPackage);
    if (isApkInstalled || isTestApkInstalled) {
      //check server apk versionName
      let apkVersion = await this.getAPKVersion(apkPath);
      let pkgVersion = await this.getInstalledPackageVersion(apkPackage);
      if (apkVersion !== pkgVersion) {
        isApkInstalled = false;
        isTestApkInstalled = false;
        await this.adb.uninstallApk(apkPackage);
        await this.adb.uninstallApk(testApkPackage);
      }
    }
    if (!isApkInstalled) {
      await this.signAndInstall(apkPath, apkPackage);
    }
    if (!isTestApkInstalled) {
      await this.signAndInstall(testApkPath, testApkPackage);
    }
  }

uiautomator2-driver 会去校验设备是否已安装以及对版本号进行判断，所以想替换设备里的版本，还需修改你编译 apk 的 version，或者提前删除设备已经安装的。

2.修改 wd 代码
既然 uiautomator2-Server 路由中只有press_keycode，没有keyevent，那可以在 wd 里添加相应的 Post 方法。
找到你项目中 node_modules 里 wd 模块，在/lib/commands.js 中添加代码如下：

/**
 * pressKeyCode(keycode, metastate, cb) -> cb(err)
 * metastate is optional
 *
 * @jsonWire POST /session/:sessionId/appium/device/press_keycode
 */
commands.pressKeyCode = function() {
    var fargs = utils.varargs(arguments);
    var cb = fargs.callback,
        keycode = fargs.all[0],
        metastate = fargs.all[1];
    var data = {keycode: keycode};
    if(metastate) { data.metastate = metastate; }
    this._jsonWireCall({
        method: 'POST'
        , relPath: '/appium/device/press_keycode'
        , data: data
        , cb: simpleCallback(cb)
    });
};

重启项目后，driver 就可以调用 pressKeyCode 方法，appium server 会将请求转发到/press_keycode，uiautomator2 server 也就可以识别。

3.修改 uiautomator2-driver
我们在分析 appium-uiautomator2-driver 时，发现作者其实是有写 keyevent 方法的，只不过调用的是 adb：

// uiautomator2 doesn't support metastate for keyevents
commands.keyevent = async function (keycode, metastate) {
  log.debug(`Ignoring metastate ${metastate}`);
  await this.adb.keyevent(keycode);
};

那么怎么才能让 appium 直接调用这个方法呢，我们发现 uiautomator2-driver 的 driver.js 里有个数组：

// NO_PROXY contains the paths that we never want to proxy to UiAutomator2 server.
// TODO:  Add the list of paths that we never want to proxy to UiAutomator2 server.
// TODO: Need to segregate the paths better way using regular expressions wherever applicable.
// (Not segregating right away because more paths to be added in the NO_PROXY list)
const NO_PROXY = [
  ['POST', new RegExp('^/session/[^/]+/touch/multi/perform')],
  ['POST', new RegExp('^/session/[^/]+/touch/perform')],
  ['POST', new RegExp('^/session/[^/]+/element')],
  ['POST', new RegExp('^/session/[^/]+/appium/element/[^/]+/value')],
  ['POST', new RegExp('^/session/[^/]+/appium/element/[^/]+/replace_value')],
  ['GET', new RegExp('^/session/[^/]+/appium/[^/]+/current_activity')],
  ['POST', new RegExp('^/session/[^/]+/appium/[^/]+/start_activity')],
  ['POST', new RegExp('^/session/[^/]+/app/[^/]')],
  ['POST', new RegExp('^/session/[^/]+/location')],
  ['GET', new RegExp('^/session/[^/]+/appium/device/system_time')],
  ['POST', new RegExp('^/session/[^/]+/appium/settings')],
  ['GET', new RegExp('^/session/[^/]+/appium/settings')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/app_installed')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/lock')],
  ['POST', new RegExp('^/session/[^/]+/appium/app/close')],
  ['POST', new RegExp('^/session/[^/]+/appium/app/launch')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/pull_file')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/push_file')],
  ['POST', new RegExp('^/session/[^/]+/appium/app/reset')],
  ['POST', new RegExp('^/session/[^/]+/appium/app/background')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/toggle_location_services')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/is_locked')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/unlock')],
  ['POST', new RegExp('^/session/[^/]+/appium/app/end_test_coverage')],
  ['GET', new RegExp('^/session/[^/]+/contexts')],
  ['POST', new RegExp('^/session/[^/]+/context')],
  ['GET', new RegExp('^/session/[^/]+/context')],
  ['POST', new RegExp('^/session/[^/]+/network_connection')],
  ['GET', new RegExp('^/session/[^/]+/network_connection')],
  ['POST', new RegExp('^/session/[^/]+/timeouts')],
  ['GET', new RegExp('^/session/[^/]+/screenshot')],
  ['GET', new RegExp('^/session/[^/]+/element/[^/]+/attribute')],
  ['GET', new RegExp('^/session/[^/]+/element/[^/]+/enabled')],
  ['GET', new RegExp('^/session/[^/]+/element/[^/]+/selected')],
  ['GET', new RegExp('^/session/[^/]+/element/[^/]+/displayed')],
  ['GET', new RegExp('^/session/[^/]+/element/[^/]+/name')],
  ['GET', new RegExp('^/session/(?!.*\/)')],
  ['POST', new RegExp('^/session/[^/]+/keys')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/hide_keyboard')],
  ['POST', new RegExp('^/session/[^/]+/log')],
  ['POST', new RegExp('^/session/[^/]+/appium/device/remove_app')],
  ['GET', new RegExp('^/session/[^/]+/appium/device/is_keyboard_shown')]
];

注释里写了， 该数组维护的是不会转发到 uiautomator2 的路由，那么，我们只需要在该数组里添加:
['POST', new RegExp('^/session/[^/]+/appium/device/keyevent')]。

p.s，该方法修改的是 appium server 依赖的 appium-uiatumator2-driver,修改后需通过命令行启动 appium，桌面程序似乎是带有缓存自制的，直接运行修改的代码不会起作用。

以上，对 appium 整个原理还不是很熟，上面的分析可能有误，敬请指出~