CODEWITHSUNDEEP
androidandroid-layoutandroid-view
user940016
user940016

Reputation: 2948

How can a view detect when it's being attached to its parent?

I have a View that needs to detect when it's being attached to its parent view.

In a ViewGroup I have the OnHierarchyChangeListener which allows me to know when a child view is being added / removed, but I need the opposite thing.

Upvotes: 16

Views: 18671

Answers (6)

okarakose
okarakose

Reputation: 3742

If you are using kotlin you can use doOnAttach extension function on View.

    view.doOnAttach {
        // TODO: Your view has a parent, you can use it now.
        (view.parent as ViewGroup)?.yourAction()
    }

Upvotes: 3

Michael Krause
Michael Krause

Reputation: 4869

Solution without having to create a custom view

If the View is one you can't or don't want to modify, you can use View.addOnAttachStateChangeListener to get hooks when the view is attached to the view hierarchy and when it is detached from the view hierarchy.

Something like:

Kotlin

view.addOnAttachStateChangeListener(object : View.OnAttachStateChangeListener {
  override fun onViewAttachedToWindow(v: View) {
    // Do stuff when view has been attached to window
  }

  override fun onViewDetachedFromWindow(v: View) {
    // Do stuff when view has been detached from window
  }
})

Java

view.addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
  @Override
  public void onViewAttachedToWindow(View v) {
    // Do stuff when view has been attached to window
  }

  @Override
  public void onViewDetachedFromWindow(View v) {
    // Do stuff when view has been detached from window
  }
});

Upvotes: 3

Nativ
Nativ

Reputation: 3150

You can look at this problem in a different angle, if you monitor the parents for attached views by implementing method onViewAdded.

Example:

public class LayoutInvokeChildAdded extends RelativeLayout {

    private OnDoneListener onDoneListener;

    public LayoutInvokeChildAdded(Context context) {
        super(context);
    }

    public LayoutInvokeChildAdded(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public LayoutInvokeChildAdded(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public void onViewAdded(View child) {
        super.onViewAdded(child);
        if (onDoneListener != null)
            onDoneListener.onDone(childe);
    }

    public void setOnDoneListener(OnDoneListener onDoneListener) {
        this.onDoneListener = onDoneListener;
    }
}

Upvotes: 0

Glaucus
Glaucus

Reputation: 958

I think if you need that kind of control it may be best to make it a fragment. That way you get access to a much more granular lifecycle.

Upvotes: 0

SylvainL
SylvainL

Reputation: 3938

Well, you have the view in OnHierarchyChangeListener, so I would suppose that you could add a callback to your views (by subclassing them with an interface) and call it from OnHierarchyChangeListener. This way, your views will be called at the same time that the OnHierarchyChangeListener is called.

However, I won't be surprised that when this happens, that many properties of your views like their dimensions might not be defined yet.

Upvotes: 0

Talha
Talha

Reputation: 12717

You can create custom view and do your stuff in its onAttachedToWindow

public class CustomView extends View {

   public CustomView(Context context) {
       super(context);
   }

   @Override
   protected void onAttachedToWindow() {
       super.onAttachedToWindow();
       Log.d("CustomView", "onAttachedToWindow called for " + getId());
       Toast.makeText(getContext(), "added", 1000).show();
   }
}

[EDIT 1]

you can ensure that your customview added to correct viewgroup which you want

@Override
 protected void onAttachedToWindow() {
    // TODO Auto-generated method stub
    super.onAttachedToWindow();

    if(((View)getParent()).getId()== R.id.relativelayout2)
    {           
        Log.d("CustomView","onAttachedToWindow called for " + getId());
        Toast.makeText(context, "added", 1000).show();          
    }

}

Upvotes: 19

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