How to handle visibility changes for a custom android view/widget

Question

I have written a custom view in android. I need to do some processing when visibility of this view is changed. Is there some listener which is called when visibility of a view/widget is changed ?

Edit:

I know how to change the visibility, would like to know if there is a listener which is called when we setVisibility on the view!

Explain a bit more, please – cgalvao1993 May 08 '13 at 14:19 — cgalvao1993, May 08 '13 at 14:19

score 19 · Accepted Answer · answered May 08 '13 at 14:30

19

Do you want to do that processing within your custom view class? If so, then why not just override the setVisibility() method, call super(), and then do your custom processing?

answered May 08 '13 at 14:30

user1676075

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marking this as answer since this solution was provided prior to blackbelt's detailed explaination – Jeevan May 08 '13 at 14:55
3

it does not work this way. For example, if you set a view's parent to be invisible, that view's visibility property still could be visible. Just practice this and you will find it's true. – LiangWang Nov 14 '15 at 14:52
This is a very limited solution. @William answer below is more general. Additionally there is a onWindowVisibilityChanged for the window. – Jerry F Mar 22 '19 at 00:13

score 18 · Answer 2 · answered May 08 '13 at 14:37

I know how to change the visibility, would like to know if there is a listener which is called when we setVisibility on the view!

you have to subclass your view/widget and override setVisibility, and register a interface on which you will recive the notification. For instance:

public class MyView extends View {

  public interface MyListener {
    public void onSetVisibilityCalled();
  }

  public void registerListener(MyListener myListener) {
    this.mListener = myListener;
  }

 public void setVisibility (int visibility) {
   super.setVisibility(visibility);
   if (mListener != null)
     mListener.onSetVisibilityCalled();
 }

}

When the parent view's visibility is changed, setVisibility won't necessarily be called. — Stephen M -on strike-, May 02 '19 at 14:35

William · Answer 3 · 2015-03-19T17:10:28.050

You have to subclass the view you want to add a listener to. You then should override onVisibilityChanged instead of setVisibility. onVisibilityChanged is triggered when the view's visibility is changed for any reason, including when an ancestor view was changed.

You will need an interface if you want a different class to be notified when your View's visibility changes.

Example:

public class MyView extends View {
  private OnVisibilityChangedListener mVisibilityListener;

  public interface OnVisibilityChangedListener {
    // Avoid "onVisibilityChanged" name because it's a View method
    public void visibilityChanged(int visibility);
  }

  public void setVisibilityListener(OnVisibilityChangedListener listener) {
    this.mVisibilityListener = listener;
  }

 protected void onVisibilityChanged (View view, int visibility) {
   super.onVisibilityChanged(view, visibility);

   // if view == this then this view was directly changed.
   // Otherwise, it was an ancestor that was changed.

   // Notify external listener
   if (mVisibilityListener != null)
     mVisibilityListener.visibilityChanged(visibility);

   // Now we can do some things of our own down here
   // ...
 }
}

score -1 · Answer 4 · answered May 08 '13 at 14:19

-1

To change the visibility of a widget, use the widget.setVisibility(View.Visible) or widget.setVisibility(View.Invisible) methods.

answered May 08 '13 at 14:19

coder

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I know how to change the visibility, would like to know if there is a listener which is called when we setVisibility on the view! – Jeevan May 08 '13 at 14:22

How to handle visibility changes for a custom android view/widget

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