问题
I have been trying to use SetActive () to turn on and off GameObjects.
I couldn't figure it out and ended up using:
GameObject.Find ("ObjectName").GetComponent<Image> ().enabled = false;
to turn off an image.
I am not trying to use the same script to turn off a GameObject that has multiple animations nested inside it.
GameObject.Find ("ObjectName").GetComponent<???> ().enabled = false;
GameObject.Find ("ObjectName").SetActive (false);
I am not sure what goes in the <>, but I have read I can do it with SetActive (), but that doesn't seem to work and gives me an "Object Reference not set to object" error.
So what is the difference between these two and how would I use them properly?
回答1:
Using GetComponent allows you to enable/disable and interact with specific components on a GameObject.
For example, you may need to disable a GameObject's rigidbody at some point, but you still want that object, and everything else on it to be active. So you could simply say:
GameObject.Find("MyObject").GetComponent<Rigidbody>().enabled = false;
Note that what goes inside the "<>" is the class name of the component you want to interact with.
For example, if you had a script you have written yourself on a gameobject called MyScript, you could grab hold of it like so:
MyScript script = GamesObject.Find("MyObject").GetComponent<MyScript>().enabled = true;
Additionally, another good use of GetComponent is reading information from a script on an object.
For example, if you had a script called Health with a public variable HitPoints on an object, another script could gain access to that information using GetComponent.
if( enemyGameObject.GetComponent<Health>().HitPoints < 0 )
{
enemyGameObject.SetActive(false);
}
Using SetActive will enable and disable a GameObject entirely. This is less expensive than deleting / making a new object, and is thus often used in techniques like Object Pooling.
For example, if you had a GameObject that you needed disabled, but you knew you were going to need it again soon, it is far less expensive to just call
MyGameObject.SetActive(false);
...
MyGameObject.SetActive(true);
Than it is to delete that object entirely, and then make a new one when you are ready for it again.
回答2:
To add up to the other answers, when a component is disabled it means the MonoBehaviour callbacks are not called anymore. So no Update, FixedUpdate, OnCollisionXXX and so on.
Awake is called when the object is created so it is obviously enabled by default at that stage. Start is called on the first run after Awake. So if you set the component off in Awake, Start will wait until you set it back on from elsewhere.
OnEnable/OnDisable are called when you modify the enabled property.
SetActive works on the GO and is pretty much a shortcut to disable all components at once.
gameObject.SetActive(false);
foreach(var comp in GetComponentsInChildren<MonoBehaviour>()){
comp.enabled = false;
}
those are fairly similar in result (maybe not in efficiency). Actually, when you set a game object on/off, the OnEnable/OnDisable of each component is called. All MonoBehaviour callbacks are not called anymore if you set the object off.
So, the choice is dependent on what you are after, if you wish to disable movement but still see the object and other actions:
GetComponent<Movement>().enabled = false;
if you wish to kill an enemy:
enemy.gameObject.SetActive(false);
Note that even though a component is disable, does not mean you cannot interact with it. You can still manually call any method on it. Consider this:
AnyComponent ac = gameObject.GetComponent<AnyComponent>();
ac.enabled = false;
ac.AnyMethod();
Valid and will do what it is meant to do considering it does not require an Update or a FixedUpdate (Physics action).
A deactivated component cannot be found with GetComponent, you can get it with GetComponentInChildren(true) since it also searches the game object and its children. I am not sure whether it returns the first found or the first active found.
myGameObject.SetActive(false); AnyComponent ac = myGameObject.GetComponent(); AnyComponent acic = myGameObject.GetComponentInChildren(true);
even though the GO has a AnyComponent attached, ac is null, acic is not (seems to be a 5.3 feature though). http://docs.unity3d.com/ScriptReference/Component.GetComponentInChildren.html
Finally, for a component to expose the tick, it needs to have a Start method in the script (don't ask why...).
回答3:
Setting .enabled turns one component on a GameObject on or off, e.g. an Image. Using SetActive() turns the whole GameObject on or off.
Choosing which to use should correspond with what you want to disable.
来源：https://stackoverflow.com/questions/34908890/what-is-the-difference-between-getcomponentimage-enabled-and-setactive-fa