手机自动化测试：Appium源码分析之跟踪代码分析五

手机自动化测试：Appium源码分析之跟踪代码分析五

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queue

我们先了解一下事件的集中处理方式，参考文章。从这篇文章可以知道，nodejs提供了一个Async库，该库就是用来处理事件的。里面就有这一个queue。
在上一篇文章我们讲到了initQueue,我们这次再来看看：

Android.prototype.initQueue = function () {

this.queue = async.queue(function (task, cb) {

var action = task.action,

params = task.params;

this.cbForCurrentCmd = cb;

if (this.adb && !this.shuttingDown) {

this.uiautomator.sendAction(action, params, function (response) {

this.cbForCurrentCmd = null;

if (typeof cb === 'function') {

this.respond(response, cb);

}

}.bind(this));

} else {

this.cbForCurrentCmd = null;

var msg = "Tried to send command to non-existent Android device, " +

"maybe it shut down?";

if (this.shuttingDown) {

msg = "We're in the middle of shutting down the Android device, " +

"so your request won't be executed. Sorry!";

}

this.respond({

status: status.codes.UnknownError.code

, value: msg

}, cb);

}

}.bind(this), 1);

};

Async库中queue的定义一般如下所示：

var q = async.queue(function(task, callback) {

log(‘worker is processing task: ‘, task.name);

task.run(callback);

}, 1);

上面定义了一个工作线程为1的队列。当队列正在处理事件时，其他事件就一直等待。所以当我们使用queue的push方法时，queue会自己唤起然后执行，如果正在执行，push添加进来的事件会等到下一次执行。

uiautomator.sendAction

上面的请求，最终调用的是devices/android/uiautomator的sendAction的方法:

UiAutomator.prototype.sendAction = function (action, params, cb) {

if (typeof params === "function") {

cb = params;

params = {};

}

var extra = {action: action, params: params};

this.sendCommand('action', extra, cb);

};

然后转向sendCommand方法

uiautomator.sendCommand

UiAutomator.prototype.sendCommand = function (type, extra, cb) {

if (this.cmdCb !== null) {

logger.warn("Trying to run a command when one is already in progress. " +

"Will spin a bit and try again");

var start = Date.now();

var timeoutMs = 10000;

var intMs = 200;

var waitForCmdCbNull = function () {

if (this.cmdCb === null) {

this.sendCommand(type, extra, cb);

} else if ((Date.now() - start) < timeoutMs) {

setTimeout(waitForCmdCbNull, intMs);

} else {

cb(new Error("Never became able to push strings since a command " +

"was in process"));

}

}.bind(this);

waitForCmdCbNull();

} else if (this.socketClient) {

this.resendLastCommand = function () {

this.sendCommand(type, extra, cb);

}.bind(this);

if (typeof extra === "undefined" || extra === null) {

extra = {};

}

var cmd = {cmd: type};

cmd = _.extend(cmd, extra);

var cmdJson = JSON.stringify(cmd) + "\n";

this.cmdCb = cb;

var logCmd = cmdJson.trim();

if (logCmd.length > 1000) {

logCmd = logCmd.substr(0, 1000) + "...";

}

this.debug("Sending command to android: " + logCmd);

this.socketClient.write(cmdJson);

} else {

cb({

status: status.codes.UnknownError.code

, value: "Tried to send command to non-existent Android socket, " +

"maybe it's shutting down?"

});

}

};

最终会向设备端的socket发送一条命令，关于设备端接受命令以及如何处理，请查看我之前写的关于appium中bootstrap源码分析相关文章