Difference between revisions of "Click through"

Latest revision as of 18:18, 2 October 2017

It's very common to have game world objects which can be clicked/ tapped on. However, if your UI is over one of those objects, you might get something called 'click through' - where both the UI and your game world object handle the click.

Why click through happens

Unity doesn't provide a way to block the built in raycast which occurs when the screen is pressed or the mouse is clicked. Click through happens for Unity's built in GUI too. So, because PowerUI can't block it from happening, both Unity's raycast and PowerUI's element resolve occur at the same time - when both happen to get handled, then the click through scenario arises.

Avoiding it

Unity GUI and older versions of PowerUI have a flag which you check from your MonoBehaviour click methods (like OnMouseDown). Due to a wider variety of events (e.g. the touch events) and as PowerUI fully supports multi-touch (which the flag route fails for), there's now two potential routes - both involve catching the event after they've passed through the UI:

Use Input.Unhandled

See also the event flow. This special EventTarget receives all events which were not handled by your UI. If you click 'through' your UI, the mouse/touch events are sent here. Grab them using addEventListener:

PowerUI.Input.Unhandled.addEventListener("mousedown",delegate(MouseEvent e){
    
    // They clicked on *nothing!* (straight 'through' the UI).
    // Send this event wherever you'd like.
    // Note that the original raycast (and any GameObject it hit) are available:
    if(e.raySuccess){
        // It hit something! Use rayHit next.

        // Get the clicked gameObject:
        GameObject go = e.rayHit.gameObject;
        
        // Try getting a MonoBehaviour called 'MyInputScript':
        MyInputScript myInput = go.GetComponent<MyInputScript>();
        
        if(myInput != null){
            // Great - forward the event to it:
            myInput.MouseDown(e);
        }
    }
    
});

PowerUI tries to give your input system as much flexibility as possible, so the above route is considered relatively low level and which allows you to pipe those events wherever you need them, but requires a little more scripting to hook it up. PowerUI.Input.Unhandled is just an EventTarget instance which you can replace with a custom object too to e.g. divert everything.

Setup an EventTarget MonoBehaviour

This is the easier route, but involves PowerUI defining more of your input system. This also has the advantage of being able to correctly handle 3D context menu's too. Firstly, tick the "Handle 3D Input" box in Window > PowerUI > Input Settings, then typically all you'll need to do is just add "MouseEvent" to e.g. OnMouseDown. Here's an example:

// A MonoBehaviour attached to a GameObject with a collider.
public class MyGameworldEvents : MonoBehaviour{
    
    public void OnMouseDown(MouseEvent e){
        // To 'convert' a method, all we've really done is add the MouseEvent parameter.
        // That makes it much better at dealing with multitouch too.
        
        // This runs when this gameobject got clicked on
        // and the UI was not.
        
    }
  
}

This way you can dispatch any event to any gameObject too:

// Create whatever event type you'd like:
MissionEvent e= new MissionEvent("missioncomplete");

// Dispatch it to a gameobject:
aGameObject.dispatchEvent(e);

// A MonoBehaviour attached to a GameObject with a collider.
public class MyGameworldEvents : MonoBehaviour{
    
    public void OnMissionComplete(MissionEvent e){
        // Your method must simply start with 'On' and accept exactly 1 event argument.
        
        // This will receive the above missioncomplete event.
    }
  
}