Understanding and implementing OnSizeChanged to get ImageView width and height

Question

So I have an ImageView that I have declared in my xml.

class.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/relativeLayout"
    tools:context=".ImageConfirmation" >

    <ImageView
        android:id="@+id/confirmationView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_alignParentTop="true"
        />

</RelativeLayout>

And my Java file looks like.

MyClass.java

public class MyClass extends Activity{

    ImageView imageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_confirmation);
        imageView = (ImageView) findViewById(R.id.confirmationView);

        }
}

Now when I try to do imageView.getWidth() and imageView.getHeight() it always returns me ZERO. So I was thinking of using the protected void onSizeChanged (int w, int h, int oldw, int oldh) from here . But I am not sure if this is the right way to do it.

If yes then how should I go about implementing it in my code structure. My class already extends an Activity so not sure how to implement the onSizeChanged.

I also tried doing

ViewTreeObserver vto = confirmationView.getViewTreeObserver();
        vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

            @Override
            public void onGlobalLayout() {
                imageViewSurfaceWidth = imageView.getWidth();
                imageViewSurfaceHeight = imageView.getHeight();
            }

        });

But this didn't work for me either. How to get the imageView width and Height.

Answer 1

You can use onSizeChange method, for this way, you should write your custom ImageView and override onSizeChange . In this method the height and width will be provided.

But attentation, this method won't be called in the before onCreate() in Activity.

I believe you can use this way to get the height and width:

imageView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            imageView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
            imageViewSurfaceWidth = imageView.getWidth();
            imageViewSurfaceHeight = imageView.getHeight();
            Log.i("activity", "width = "+imageViewSurfaceWidth+", height = "+imageViewSurfaceHeight);
        }
    });

I use this way to for this purpose for a long time, and it works well.

You said this doesn't work, and I think it should not happen, maybe you should log the height and width you get in onGlobalLayout() to see what is wrong.

Answer 2

I use this inside main activity:

@Override
public void onWindowFocusChanged(boolean hasFocus) {

 super.onWindowFocusChanged(hasFocus);
main_width=main_view.getWidth();
main_height=main_view.getHeight();


}

where main_view is your imageView.