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可覆盖函数¶

Godot 的 Node 类提供了虚函数，你可以通过覆盖虚函数来在每帧或发生特定事件时更新节点，比如进入场景树时。

本文档中会展示你会经常用到的那些。

参见

这些函数在引擎内部会依赖 Godot 的底层通知系统。要了解相关学习，请参阅 Godot 通知。

除了类的构造函数之外，还有两个函数可以用来初始化并获取节点：_enter_tree() 和 _ready()。

节点进入场景树时就会被激活，引擎会调用其 _enter_tree() 方法。该节点的子项可能还不是活动场景的一部分。因为你可以从场景树中移除节点然后重新添加，在一个节点的生命期中，这个函数可能会被调用多次。

你在大多数时候用的其实是 _ready()。这个函数只会在节点的生命期中被调用一次，在 _enter_tree() 之后。_ready() 可以保证所有子项都已经进入了场景树，所以你可以安全地去调用 get_node()。

参见

要学习更多关于节点引用的知识，请阅读节点与场景实例。

另一个有关的回调是 _exit_tree()，引擎会在节点退出场景树时调用。既可以是你调用 Node.remove_child() 时，也可以是你释放这个节点时。

# Called every time the node enters the scene tree.
func _enter_tree():
    pass

# Called when both the node and its children have entered the scene tree.
func _ready():
    pass

# Called when the node is about to leave the scene tree, after all its
# children received the _exit_tree() callback.
func _exit_tree():
    pass

// Called every time the node enters the scene tree.
public override void _EnterTree()
{
    base._EnterTree();
}

// Called when both the node and its children have entered the scene tree.
public override void _Ready()
{
    base._Ready();
}

// Called when the node is about to leave the scene tree, after all its
// children.
public override void _ExitTree()
{
    base._ExitTree();
}

虚函数 _process() 和 _physics_process() 可以分别用来对节点进行每帧和每物理帧的更新。要了解更多信息，请阅读专门的文档：空闲处理与物理处理。

# Called every frame, as often as possible.
func _process(delta):
    pass

# Called every physics frame.
func _physics_process(delta):
    pass

public override void _Process(double delta)
{
    // Called every frame, as often as possible.
    base._Process(delta);
}

public override void _PhysicsProcess(double delta)
{
    // Called every physics frame.
    base._PhysicsProcess(delta);
}

还有两个关键的内置节点回调函数 Node._input() 和 Node._unhandled_input()。两者都可以用来接收并处理单独的输入事件。如果按键、鼠标点击等事件没有被 _input() 回调或用户界面组件处理，_unhandled_input() 方法才会收到这个事件。游戏中的输入通常是使用后者处理的。_input() 回调可以用来在 _unhandled_input() 获取前拦截并处理输入事件。

要学习更多关于 Godot 中输入的内容，请参阅输入章节。

# Called once for every event.
func _unhandled_input(event):
    pass

# Called once for every event, before _unhandled_input(), allowing you to
# consume some events.
func _input(event):
    pass

// Called once for every event.
public override void _UnhandledInput(InputEvent @event)
{
    base._UnhandledInput(@event);
}

// Called once for every event, before _unhandled_input(), allowing you to
// consume some events.
public override void _Input(InputEvent @event)
{
    base._Input(@event);
}

There are some more overridable functions like Node._get_configuration_warnings(). Specialized node types provide more callbacks like CanvasItem._draw() to draw programmatically or Control._gui_input() to handle clicks and input on UI elements.