How do I programmatically center a view on the layout?

Question

I am makig some game to learn more about Java and AStudio. I need to center one view onto another view. Boths views are ConstraintLayouts. I've already tried MATCH_PARENT or WRAP_CONTENT along with changing the size but the smaller view will always wrap to 0,0 position in parent view. If I use "setX/setY" on the child view, will it work on the parent view or the main view Layout? Anyways I know its an android view attribute to center the child somehow using gravity or smth but I couldn't find the correct answer anywhere.

public class GameField extends ConstraintLayout {...    
public class GameUnit extends ConstraintLayout {...
...
...
private void deployClick(){
        int sizeUnit = 960/boardSizeX;
        int x = 4;
        for (int i =0; i<x;i++){
            int randCounter = randomNum.nextInt(counterFields);
            counterUnits++;
            gameUnit[counterUnits] = new GameUnit(this,randomNum.nextInt(4),randomNum.nextInt(10),randomNum.nextInt(10));
            gameUnit[counterUnits].setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
            gameUnit[counterUnits].setLayoutParams(new android.view.ViewGroup.LayoutParams(sizeUnit-5,sizeUnit-5));
            gameField[randCounter].addView(gameUnit[counterUnits]);
            gameField[randCounter].setUnitAdded(true);
            deployClicked = true;
        }
    }

Answer 1

Rule of thumb for LayoutParam s: they are named after the parent layout. So for the inner custom View you need to set ConstraintLayout.LayoutParams :

ConstraintLayout.LayoutParams lp = new ConstraintLayout.LayoutParams(sizeUnit - 5, sizeUnit - 5);
gameUnit[counterUnits].setLayoutParams(lp);
gameField[randCounter].addView(gameUnit[counterUnits]);

Since your outer custom View extends from ConstraintLayout , you can use a ConstraintSet to position the inner View correctly. They use View id's so you need to give your dynamically added View s an id by calling setId(View.generateViewId()) on them. Then you can proceed as follows:

int unitId = gameUnit[counterUnits].getId();
int fieldId = gameField[randCounter].getId();

ConstraintSet cs = new ConstraintSet();
cs.connect(unitId, ConstraintSet.START, fieldId, ConstraintSet.START)
cs.connect(unitId, ConstraintSet.END, fieldId, ConstraintSet.END)
cs.connect(unitId, ConstraintSet.TOP, fieldId, ConstraintSet.TOP)
cs.connect(unitId, ConstraintSet.BOTTOM, fieldId, ConstraintSet.BOTTOM)
cs.constrainHeight(unit.id, lp.height);
cs.constrainWidth(unit.id, lp.width);

First add the unit View to the field View , then call

cs.applyTo(gameField[randCounter])   
gameField[randCounter].setUnitAdded(true)
deployClicked = true