Get width of AlertDialog in pixels or dp

you can only get widht and height of view, So if its custom dialog, take its root view kindly follow the example

RelativeLayout rl = (RelativeLayout) dialog.findViewById(R.id.root_relative_layout);

Here relative layout is the parent view and component are in it.

Now to get height and width do this:-

int width = rl.getWidth();
int height = rl.getHeight();

To set widht and height do this

 AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setView(layout);
    builder.setTitle("Title");
    alertDialog = builder.create();
    alertDialog.getWindow().setLayout(600, 400); //Controlling width and height.
    alertDialog.show();

OR

WindowManager.LayoutParams lp = new WindowManager.LayoutParams();
lp.copyFrom(alertDialog.getWindow().getAttributes());
lp.width = 150;
lp.height = 500;
lp.x=-170;
lp.y=100;
alertDialog.getWindow().setAttributes(lp);

Replace below code:

dialog.getWindow().setLayout(getResources().getDimensionPixelSize(R.dimen.layout_height_400dp), WindowManager.LayoutParams.MATCH_PARENT);