How to get size of an image from xml in android

Question

I am developing an android application that uses an image and has a constraint layout. The attributes for height and width are set to "wrap-content" meaning they are not fixed. On that image, I am creating a graph using circles. For that, I should know the exact values of the width and height of the image. How can I get the values of width and height from XML to Java?

Answer 1

You can use getWidth and getHeight to get dimensions of any view (in this case constraint layout) at runtime.
But be carful, before using this two methods you have to make sure that the view (constraint layout) is already created, otherwise it gonna return 0, witch means you can't call them in onCreate.
So the correct way to do it is to wait for the view to be created then get its size. Like this :

create this method

public static void runJustBeforeBeingDrawn(final View view, final Runnable runnable) {
final OnPreDrawListener preDrawListener = new OnPreDrawListener() {
    @Override
    public boolean onPreDraw() {
        view.getViewTreeObserver().removeOnPreDrawListener(this);
        runnable.run();
        return true;
    }
};
view.getViewTreeObserver().addOnPreDrawListener(preDrawListener); 
}

Then call it when u need to get the dimensions

runJustBeforeBeingDrawn(yourView, new Runnable() {
        @Override
        public void run() {
            //Here you can safely get the view size (use "getWidth" and "getHeight"), and do whatever you wish with it
        }
    });

Related to your question :
View's getWidth() and getHeight() returns 0
Determining the size of an Android view at runtime