How to detect a layout resize?

Question

Dianne Hackborn mentioned in a couple threads that you can detect when a layout as been resized, for example, when the soft keyboard opens or closes. Such a thread is this one... http://groups.google.com/group/android-developers/browse_thread/thread/d318901586313204/2b2c2c7d4bb04e1b

However, I didn't understand her answer: "By your view hierarchy being resized with all of the corresponding layout traversal and callbacks."

Does anyone have a further description or some examples of how to detect this? Which callbacks can I link into in order to detect this?

Thanks

Answer 1

One way is View.addOnLayoutChangeListener. There's no need to subclass the view in this case. But you do need API level 11. And the correct calculation of size from bounds (undocumented in the API) can sometimes be a pitfall. Here's a correct example:

view.addOnLayoutChangeListener( new View.OnLayoutChangeListener()
{
    public void onLayoutChange( View v,
      int left,    int top,    int right,    int bottom,
      int leftWas, int topWas, int rightWas, int bottomWas )
    {
        int widthWas = rightWas - leftWas; // Right exclusive, left inclusive
        if( v.getWidth() != widthWas )
        {
            // Width has changed
        }
        int heightWas = bottomWas - topWas; // Bottom exclusive, top inclusive
        if( v.getHeight() != heightWas )
        {
            // Height has changed
        }
    }
});

Another way (as dacwe answers) is to subclass your view and override onSizeChanged.

Answer 2

Override onSizeChanged in your View!

Answer 3

With Kotlin extensions:

inline fun View?.onSizeChange(crossinline runnable: () -> Unit) = this?.apply {
    addOnLayoutChangeListener { _, left, top, right, bottom, oldLeft, oldTop, oldRight, oldBottom ->
        val rect = Rect(left, top, right, bottom)
        val oldRect = Rect(oldLeft, oldTop, oldRight, oldBottom)
        if (rect.width() != oldRect.width() || rect.height() != oldRect.height()) {
            runnable();
        }
    }
}

Use thus:

myView.onSizeChange { 
     // Do your thing...
}

Answer 4

My solution is to add an invisible tiny dumb view at the end of of the layout / fragment (or add it as a background), thus any change on size of the layout will trigger the layout change event for that view which could be catched up by OnLayoutChangeListener:

Example of adding the dumb view to the end of the layout:

 <View 
    android:id="@+id/theDumbViewId"
    android:layout_width="1dp"
    android:layout_height="1dp"
     />

Listen the event:

    View dumbView = mainView.findViewById(R.id.theDumbViewId);
    dumbView.addOnLayoutChangeListener(new OnLayoutChangeListener() {
        @Override
        public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
            // Your code about size changed
        }
    });

Answer 5

Thank to https://stackoverflow.com/users/2402790/michael-allan this is the good and simple way if you don't want to override all your views. As Api has evolved I would suggest this copy paste instead:

    String TAG="toto";
    ///and last listen for size changed
    YourView.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
        @Override
        public void onLayoutChange(View v,
                                   int left, int top, int right, int bottom,
                                   int oldLeft, int oldTop, int oldRight, int oldBottom) {

           boolean widthChanged = (right-left) != (oldRight-oldLeft);
            if( widthChanged )
            {
                // width has changed
                Log.e(TAG,"Width has changed new width is "+(right-left)+"px");
            }
            boolean heightChanged = (bottom-top) != (oldBottom-oldTop);
            if( heightChanged)
            {
                // height has changed
                Log.e(TAG,"height has changed new height is "+(bottom-top)+"px");
            }
        }
    });

Answer 6

View.doOnLayout(crossinline action: (view: View) -> Unit): Unit

See docs.

Performs the given action when this view is laid out. If the view has been laid out and it has not requested a layout, the action will be performed straight away, otherwise the action will be performed after the view is next laid out.

The action will only be invoked once on the next layout and then removed.

Answer 7

Kotlin version base on @Michael Allan answer to detect layout size change

binding.root.addOnLayoutChangeListener { view, left, top, right, bottom, oldLeft, oldTop, oldRight, oldBottom ->
    if(view.height != oldBottom - oldTop) {
        // height changed
    }
    if(view.width != oldRight - oldLeft) {
        // width changed
    }
}

Answer 8

Other answers are correct, but they didn't remove OnLayoutChangeListener. So, every time this listener was called, it added a new listener and then called it many times.

private fun View.onSizeChange(callback: () -> Unit) {
    addOnLayoutChangeListener(object : OnLayoutChangeListener {
        override fun onLayoutChange(
            view: View?,
            left: Int,
            top: Int,
            right: Int,
            bottom: Int,
            oldLeft: Int,
            oldTop: Int,
            oldRight: Int,
            oldBottom: Int,
        ) {
            view?.removeOnLayoutChangeListener(this)
            if (right - left != oldRight - oldLeft || bottom - top != oldBottom - oldTop) {
                callback()
            }
        }
    })
}

Answer 9

If your like me and you came to this page and

1. addOnLayoutChangeListener gave you functionality you needed but caused an infinite list of "requestLayout() improperly called .... running second layout pass" messages to fill your logcat and ...
2. Adding removingOnLayoutChangeListener(this) broke the functionality you had in 1) despite fixing the repeated logcat message then this might work.

Its a mix of what Slion and Tony suggested.

1. Create a ResetDetectorCallback interface with abstract method resizeAction.

2. Create a simple custom view ResetDetector with an instance of the ResetDetectorCallback, a setResetDetectorCallback mehtod, and override its onSizeChange() method to invok the resetDectectorCallback.resizeAction().

3. In the layout place an instance of the ResetDetectorView with an id, width="match_parent", height="match_parent", and in my case I also constrained it.

4. Then in the code (mine was a Fragment since I'm adopting the Single Activity methodology) let that class implement the ResetDetectorCallback, set the resetDetectorView from that class's layout to use "this", and implement the resizeAction in that class.

And in my case its finally working the way I want now. On a Desktop emulator I can resize that Window as much as I want and it appears tobe accurately adjusting the layout accordingly to the way I want and the logcat is not being overloaded with "requestLayout() improperly called .... running second layout pass" messages.

There is probably a better way, perhaps with ViewModels and mutableStateObservers, but I'm not familiar enough with those yet. I hope this helps someone somewhere. And thanks to all the contributors above even if your technique didn't work for me.