View source for ZH-CN/脚本编写介绍 - 带有图形界面

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在MTA:SA中有一个重要的特点，那就是可以制作自定义的GUI(Graphic User Interface)。GUI由窗口，按钮，编辑框，复选框等组成，拥有在图形环境中大部分的基础控件。它们可以在玩家正在游戏的时候显示，常常被用来代替传统命令的输入和输出。

[[Image:AdminGUI.png|thumb|管理员后台GUI]]

==一个做登陆窗口的教程==
在这个教程中我们会使用两个编辑框和一个按钮制作一个登录窗口。 窗口会在玩家加入游戏的时候出现，一旦按钮被点击，玩家将会被出生。 这个教程会继续我们在 [[Scripting Introduction|脚本介绍]] 中制作的游戏模式''（如果你已经使用了 [[Scripting Introduction|脚本介绍]]，你需要在你的代码中移除或者注释掉在 "joinHandler" 行的 [[spawnPlayer]] 函数， 我们也将会在这个教程中使用一个gui替换掉它）''。 我们也会接触一下客户端脚本的编辑. 

===画一个窗口===
所有的GUI只能在客户端制作。 这是一个很好的练习机会来把所有客户端脚本放在分开的目录。

浏览到目录 /你的MTA服务端目录/mods/deathmatch/resources/myserver/ , 然后创建一个名为 "client" 的目录。 在 /client/ 目录下, 创建一个文件，文件名为 "gui.lua". 

在这个文件里，我们将会写一个画窗口的函数。使用[[guiCreateWindow]]来创建一个窗口：
<syntaxhighlight lang="lua">
function createLoginWindow()
	-- 定义窗口的X和Y坐标
	local X = 0.375
	local Y = 0.375
	-- 定义窗口的宽度和高度
	local Width = 0.25
	local Height = 0.25
        -- 创建一个窗口，并且把它放入变量 'wdwLogin' 里
        -- 点击这个函数的名字可以阅读这个函数的相关信息
	wdwLogin = guiCreateWindow(X, Y, Width, Height, "请登录", true)
end
</syntaxhighlight>

===相对和绝对坐标===
注意：传给 guiCreateWindow 的最后一个参数在上面的例子中是 ''true''。这个表明了窗口的坐标和尺寸都是 '''相对的'''，也就是说他们是一个相对于屏幕大小的 ''百分比''。我来解释一下：如果屏幕最左侧是0，那么最右侧就是1，那么X坐标为0.5将代表着屏幕中央。同理，屏幕顶部和底部也是一样的，最顶部为0，最底部为1，Y坐标为0.2则代表着是屏幕高度的20%。宽度和高度也是一样的道理（宽度为0.5则意味着窗口是屏幕的一半宽）。

另外的，也可以用 '''绝对的''' （将传入 guiCreateWindow 的最后一个参数改为 ''false'' 即可）。绝对值被计算为父级的左上角开始到右下角的像素总数（如果没有GUI元素指定父级，那么父级是屏幕本身）. 如果我们假设屏幕的分辨率为1920*1200，那么从屏幕左边开始为0像素，到屏幕右边为1920像素，X坐标为960代表屏幕的中点。同理，屏幕顶部为0，到屏幕底部则为1200，Y坐标为20代表着距离屏幕顶部的20个像素。宽度和高度也是相同的道理（宽度为50则意味着窗口为50个像素宽）。 ''你可以使用 [[guiGetScreenSize]] 和一点数学来计算某些绝对坐标。''

使用相对值和绝对值的不同点非常简单：使用绝对值创建gui经常精确地保持着相同的像素大小和坐标，然而使用相对值创建gui经常是与它父级gui大小的比值。

当你用手敲代码的时候，绝对值一般是更容易维护的。然而你的选择是根据你的目的而变化的。

由于本介绍的目的，我们将使用相对值。

===Adding the components===
Next, we'll add the text labels (saying "username:" and "password:"), edit boxes (for entering your data) and a button to log in.

To create buttons we use [[guiCreateButton]] and to create edit boxes use [[guiCreateEdit]]:

'''Note that we are now writing more code for our existing 'createLoginWindow' function. This is not a new function and is meant to replace what you already have.''' 
<syntaxhighlight lang="lua">
function createLoginWindow()
	local X = 0.375
	local Y = 0.375
	local Width = 0.25
	local Height = 0.25
	wdwLogin = guiCreateWindow(X, Y, Width, Height, "Please Log In", true)
	
	-- define new X and Y positions for the first label
	X = 0.0825
	Y = 0.2
	-- define new Width and Height values for the first label
	Width = 0.25
	Height = 0.25
	-- create the first label, note the final argument passed is 'wdwLogin' meaning the window
	-- we created above is the parent of this label (so all the position and size values are now relative to the position of that window)
	guiCreateLabel(X, Y, Width, Height, "Username", true, wdwLogin)
	-- alter the Y value, so the second label is slightly below the first
	Y = 0.5
	guiCreateLabel(X, Y, Width, Height, "Password", true, wdwLogin)
	

	X = 0.415
	Y = 0.2
	Width = 0.5
	Height = 0.15
	edtUser = guiCreateEdit(X, Y, Width, Height, "", true, wdwLogin)
	Y = 0.5
	edtPass = guiCreateEdit(X, Y, Width, Height, "", true, wdwLogin)
	-- set the maximum character length for the username and password fields to 50
	guiEditSetMaxLength(edtUser, 50)
	guiEditSetMaxLength(edtPass, 50)
	
	X = 0.415
	Y = 0.7
	Width = 0.25
	Height = 0.2
	btnLogin = guiCreateButton(X, Y, Width, Height, "Log In", true, wdwLogin)
	
	-- make the window invisible
	guiSetVisible(wdwLogin, false)
end
</syntaxhighlight>
Note that every GUI component created is a child of the window, this is done by specifying the parent element (wdwLogin, in this case) when creating the component. 

This is very useful because not only does it mean that all the components are attached to the window and will move with it, but also that any changes done to the parent window will be applied down the tree to these child components. For example, we can now hide all of the GUI we just created by simply hiding the window:
<syntaxhighlight lang="lua">
guiSetVisible(wdwLogin, false) --hides all the GUI we made so we can show them to the player at the appropriate moment. 
</syntaxhighlight>

===Using the function we wrote===
The createLoginWindow function is now complete, but it won't do anything until we call it. It is recommended to create all GUI when the client resource starts, hide them, and show them to the player later when needed. Therefore, we'll write an event handler for "[[onClientResourceStart]]" to create the window:
<syntaxhighlight lang="lua">
-- attach the event handler to the root element of the resource
-- this means it will only trigger when its own resource is started
addEventHandler("onClientResourceStart", getResourceRootElement(), 
	function ()
		createLoginWindow()
	end
)	
</syntaxhighlight>

As this is a log in window, we now need to show the window when the player joins the game. 
This can be done using the same event, "[[onClientResourceStart]]", so we can modify the above code to include showing the window:

'''Note that we are now writing more code for our existing 'onClientResourceStart' handler. This is not a new event handler and is meant to replace what you already have.''' 
<syntaxhighlight lang="lua">
addEventHandler("onClientResourceStart", getResourceRootElement(), 
	function ()
		-- create the log in window and its components
		createLoginWindow()

		-- output a brief welcome message to the player
                outputChatBox("Welcome to My MTA:SA Server, please log in.")

		-- if the GUI was successfully created, then show the GUI to the player
	        if (wdwLogin ~= nil) then
			guiSetVisible(wdwLogin, true)
		else
			-- if the GUI hasnt been properly created, tell the player
			outputChatBox("An unexpected error has occurred and the log in GUI has not been created.")
	        end 

		-- enable the players cursor (so they can select and click on the components)
	        showCursor(true)
		-- set the input focus onto the GUI, allowing players (for example) to press 'T' without the chatbox opening
	        guiSetInputEnabled(true)
	end
)	
</syntaxhighlight>

Note that we have a simple security check before making the window visible, so in the unlikely event that the window has not been created, meaning wdwLogin is not a valid element, we don't get an error and just inform the player what has happened. 
In the next step, we will create the button functionality for the log in button.

==Scripting the button==
Now that we have created our GUI and shown it to the player, we need to make it work. 

===Detecting the click===
When the player clicks on any part of the GUI, the event "[[onClientGUIClick]]" will be triggered for the GUI component you clicked on. This allows us to easily detect any clicks on the GUI elements we want to use.
For example, we can attach the event to the btnLogin button to catch any clicks on it:
<syntaxhighlight lang="lua">
-- attach the event onClientGUIClick to btnLogin and set it to trigger the 'clientSubmitLogin' function
addEventHandler("onClientGUIClick", btnLogin, clientSubmitLogin, false)
</syntaxhighlight>
'''Note the final argument passed is "false". This indicates that the event will only trigger directly on btnLogin, not if the event has propagated up or down the tree. Setting this to "true" while attaching to gui elements will mean that clicking on any element in the same branch will trigger this event.'''

This line of code can now be added inside the createLoginWindow function. It is a common mistake to try and attach events to non-existant GUI elements, so make sure you always attach your events '''after''' the gui element (in this case, the button) has been created:

'''Note that we are now writing more code for our existing 'createLoginWindow' function.''' 
<syntaxhighlight lang="lua">
function createLoginWindow()
	-- create all our GUI elements
	...

	-- now add our onClientGUIClick event to the button we just created
	addEventHandler("onClientGUIClick", btnLogin, clientSubmitLogin, false)
</syntaxhighlight>

===Managing the click===
Now that we can detect when the player clicks on the button, we need to write code to manage what happens when they do.
In our [[onClientGUIClick]] event handle, we told it to call the function clientSubmitLogin whenever btnLogin is clicked.
Therefore, we can now use the function clientSubmitLogin to control what happens when the button is clicked:
<syntaxhighlight lang="lua">
-- create the function and define the 'button' and 'state' parameters
-- (these are passed automatically by onClientGUIClick)
function clientSubmitLogin(button,state)
	-- if our login button was clicked with the left mouse button, and the state of the mouse button is up
	if button == "left" and state == "up" then
		-- move the input focus back onto the game (allowing players to move around, open the chatbox, etc)
		guiSetInputEnabled(false)
		-- hide the window and all the components
		guiSetVisible(wdwLogin, false)
		-- hide the mouse cursor
		showCursor(false)
	end
end
</syntaxhighlight>
Now, when the button is clicked, the window will be hidden and all controls will be returned to the player. Next, we will tell the server to allow the player to spawn.

===Triggering the server===
Triggering the server can be done using [[triggerServerEvent]]. This allows you to trigger a specified event on the server from the client. The same can be done in reverse using [[triggerClientEvent]].
Here, we use the [[triggerServerEvent]] function to call our own custom event on the server, named "submitLogin", which will then control the spawning of the player serverside.

'''Note that we are now writing more code for our existing 'clientSubmitLogin' function. This is not a new function and is meant to replace what you already have.''' 
<syntaxhighlight lang="lua">
function clientSubmitLogin(button,state)
	if button == "left" and state == "up" then
		-- get the text entered in the 'username' field
		local username = guiGetText(edtUser)
		-- get the text entered in the 'password' field
		local password = guiGetText(edtPass)

		-- if the username and password both exist
		if username and password then
			-- trigger the server event 'submitLogin' and pass the username and password to it
			triggerServerEvent("submitLogin", getRootElement(), username, password)

			-- hide the gui, hide the cursor and return control to the player
			guiSetInputEnabled(false)
			guiSetVisible(wdwLogin, false)
			showCursor(false)
		else
			-- otherwise, output a message to the player, do not trigger the server
			-- and do not hide the gui
			outputChatBox("Please enter a username and password.")
		end
	end
end
</syntaxhighlight>

===Creating the serverside event===
At this point we now have all the code needed on the client side, so open up your serverside 'script.lua' file (from the [[Scripting Introduction|Introduction to Scripting]]) or another suitable serverside file to work with.

On the server side, recall that we are spawning the player as soon as they login.
So, first of all, we will need to define the custom event that we used before on the client. This can be done using [[addEvent]] and [[addEventHandler]].
<syntaxhighlight lang="lua">
-- create our loginHandler function, with username and password parameters (passed from the client gui)
function loginHandler(username,password)

end

-- define our custom event, and allow it to be triggered from the client ('true')
addEvent("submitLogin",true)
-- add an event handler so that when submitLogin is triggered, the function loginHandler is called
addEventHandler("submitLogin",root,loginHandler)
</syntaxhighlight>

===Logging in===
Now we have a function that is called through the custom event 'submitLogin', we can start to work on logging in and spawning the player, using our 'loginHandler' function:
<syntaxhighlight lang="lua">
function loginHandler(username,password)
	-- check that the username and password are correct
	if username == "user" and password == "apple" then
		-- the player has successfully logged in, so spawn them
		if (client) then
			spawnPlayer(client, 1959.55, -1714.46, 10)
			fadeCamera(client, true)
                        setCameraTarget(client, client)
			outputChatBox("Welcome to My Server.", client)
		end
	else
		-- if the username or password are not correct, output a message to the player
		outputChatBox("Invalid username and password. Please re-connect and try again.",client)
        end			
end

addEvent("submitLogin",true)
addEventHandler("submitLogin",root,loginHandler)
</syntaxhighlight>
'''For the purposes of this tutorial, a very basic username and password system is shown. For a more comprehensive alternative, you can use the Account System or a MySQL database.'''

Also note the use of the variable "client", it's an internal variable used by MTA to identify the player who triggered the event. 


Finally, do not forget to include the new gui.lua file in the meta.xml of the main resource, and label it as a client script:
<syntaxhighlight lang="xml">
<script src="client/gui.lua" type="client" />
</syntaxhighlight>


At this point, we now have a basic login window that checks the player's username and password when the login button is clicked. If they are correct, the player is automatically spawned.

For further help with GUI, see the [[:Category:GUI_Tutorials|GUI tutorials]].

[[Category:GUI_Tutorials]]
[[it:Introduzione_allo_scripting_della_GUI]]
[[ru:Introduction to Scripting the GUI]]
[[es:Introducción a la Programación de GUI]]