Finding the Value of a Layout's Height and Width

Question

I am trying to get the height and width of a table layout and use that to set the height and width of my buttons. I use the following code to achieve this:

ViewGroup.LayoutParams params = new TableLayout.LayoutParams();
params.width = params.width/3;
params.height = params.width;

The code however does not work and I am unsure as of to why.

Maybe the answer is here? https://stackoverflow.com/questions/21926644/get-height-and-width-of-a-layout-programmatically — John T, Jun 21 '18 at 11:05
Are you setting the params to the view? like `view.setLayoutParams(params)` also you have not defined `width` and `height` parameters in layout params therefore it would be `0/3` and `0` — HawkPriest, Jun 21 '18 at 11:06

score 4 · Answer 1 · answered Jun 21 '18 at 11:07

4

You're using the same params Object which are also empty. Your code should be like this

ViewGroup.LayoutParams btnParams = btn.getLayoutParams();

ViewGroup.LayoutParams params = tableLayout.getLayoutParams();
btnParams.width = params.width/3;
btnParams.height = params.width;
btn.setLayoutParams(btnParams)

answered Jun 21 '18 at 11:07

Niza Siwale

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When I do that, my app crashes and I get this error message: java.lang.NullPointerException: Attempt to write to field 'int android.view.ViewGroup$LayoutParams.width' on a null object reference – Popolok11 Jun 21 '18 at 11:26
Is your tableLayout initialized? i.e does it have a parent with a context? – Niza Siwale Jun 21 '18 at 11:27
I set up my table view in the activity_main.xml file, so I think it's initialized. – Popolok11 Jun 21 '18 at 11:34
What about your button? – Niza Siwale Jun 21 '18 at 11:38
My button is set up as `Button b = new Button(this);` – Popolok11 Jun 21 '18 at 11:46
You have to add it to a view after you create the button. The params come from the layouts parent. Add your button to a parent first – Niza Siwale Jun 21 '18 at 11:58
Even after I add the buttons, the app still crashes. – Popolok11 Jun 21 '18 at 12:27

score 1 · Accepted Answer · answered Jun 21 '18 at 11:44

when onCreate is executed in your Activity, the UI has not been drawn to the screen yet, so nothing has dimensions yet since they haven't been laid out on the screen. When setContentView is called, a message is posted to the UI thread to draw the UI for your layout, but will happen in the future after onCreate finishes executing. Posting a Runnable to the UI thread will put the Runnable at the end of the message queue for the UI thread, so will be executed after the screen has been drawn,thus everything has dimensions. (that's why you got a NullPointerException from Niza Siwale answer)

btn.post(new Runnable() {
        @Override
        public void run() {
            TableLayout myTableLayout = findViewById(R.id.idOfTheTableLayout);
            int width = myTableLayout.getWidth();
            int height = myTableLaout.getHeight();

            ViewGroup.LayoutParams params = btn.getLayoutParams();
            params.height = height;
            params.width = width;
            btn.setLayoutParams(params);
        }
}

hope it works.

after initializing your button in the onCreate method (Button btn = findViewById(R.id.btnId)) you can then use the code I posted (inside the onCreate method). As I mentioned in my explanation Runnable is used to separate your code. That way you make sure to get the width and hight only after the screen was drawn. Otherwise you always trying to get the dimensions of a null object because it wasn't initialized yet. — user 007, Jun 21 '18 at 11:57

Finding the Value of a Layout's Height and Width

2 Answers2