Android view layout_width - how to change programmatically?

This is my view, and I wish to change layout_width to "10dip". How do I do so programmatically? Note, this is not a LinearLayout, it's a View.

<View 
    android:id="@+id/nutrition_bar_filled" 
    android:background="@drawable/green_rectangle" 
    android:layout_height="30dp"
    android:layout_width="50dp"/>		

I know about LayoutParams. How do I use it to set the width to 10dip?

I believe your question is to change only width of view dynamically, whereas above methods will change layout properties completely to new one, so I suggest to getLayoutParams() from view first, then set width on layoutParams, and finally set layoutParams to the view, so following below steps to do the same.

View view = findViewById(R.id.nutrition_bar_filled);
LayoutParams layoutParams = view.getLayoutParams();
layoutParams.width = newWidth;
view.setLayoutParams(layoutParams);

You can set height and width like this also:

viewinstance.setLayoutParams(new LayoutParams(width, height));

Or simply:

view.getLayoutParams().width = 400;
view.requestLayout();

try using

View view_instance = (View)findViewById(R.id.nutrition_bar_filled);
view_instance.setWidth(10);

use Layoutparams to do so where you can set width and height like below.

LayoutParams lp = new LayoutParams(10,LayoutParams.wrap_content);
View_instance.setLayoutParams(lp);

androidx (core-ktx) contains an extension function to update layout params, for example:

view.updateLayoutParams<ConstraintLayout.LayoutParams> {
    width = ConstraintLayout.LayoutParams.MATCH_PARENT
    // or wrap_content
    width = ConstraintLayout.LayoutParams.WRAP_CONTENT
    // or size measured in pixels
    width = 200 
}