Android draw() is not being called when new keyword is used to instantiate an object of customview

Question

I have a custom view with a corresponding custom layout xml which I want to display in a list view (so I can have multiple of these in a list).

As a test I did this in onCreate():

cstmView s = findViewById(R.id.card);
s.setImg(R.drawable.ac);

with:

<views.cstmView
        android:layout_width="395dp"
        android:layout_height="72dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

So I know that the view is being initialized and drawn from cstmView.java

However, I want to create a list view so I can have multiple cstmView in a scrollable list. This is what I did ( as a test I just put one cstmView in the list view):

Listv = new ArrayList<>();
//adding just one cstmview
Listv.add(new cstmView(this.getApplicationContext()));
//this is my custom adapter to accept cstm layour rathern than a textview
cstmAdapter adapter = new cstmAdapter(this, R.layout.cstm_view, ListV);
ListView cstmListView = findViewById(R.id.cstmListView);
cstmListView(adapter);

Although this is putting the cstmView in list, it is not running the overridden draw function in cstmView.

I think the problem is with new cstmView(this.getApplicationContext()) because the same problem arises with or without the list view. does the new keyword not run draw() ?

this is the method that should be calling draw in cstmView.java

public void init(Context context){
    System.out.println("INIT");
    // To instantiate an XML layout file from the already configured R.layout
    LayoutInflater.from(context).inflate(R.layout.cstm_view, this);

    // Get elements in layout

    text = (TextView)findViewById(R.id.title);
    back = (ImageView)findViewById(R.id.img);

    DisplayMetrics metrics = context.getResources().getDisplayMetrics();

    // to convert
    cornerRadius = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, CORNER_RADIUS, metrics);

    paint = new Paint(Paint.ANTI_ALIAS_FLAG);

    maskPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
    maskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

    // to draw the above
    setWillNotDraw(false);

}

and then the on draw function creates some bitmaps and so on...

 @Override
public void draw(Canvas canvas) {
    System.out.println("DRAW");
    // create a bitmap with this context height and width
    Bitmap offscreenBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
    Canvas offscreenCanvas = new Canvas(offscreenBitmap);

    super.draw(offscreenCanvas);

    if (maskBitmap == null) {
        maskBitmap = createMask(getWidth(), getHeight());
    }

    offscreenCanvas.drawBitmap(maskBitmap, 0f, 0f, maskPaint);
    canvas.drawBitmap(offscreenBitmap, 0f, 0f, paint);


}

private Bitmap createMask(int width, int height) {

    System.out.println("CREATE MASK");
    Bitmap mask = Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8);
    Canvas canvas = new Canvas(mask);

    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(Color.WHITE);

    canvas.drawRect(0, 0, width, height, paint);

    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
    canvas.drawRoundRect(new RectF(0, 0, width, height), cornerRadius, cornerRadius, paint);

    return mask;
}

update

calling invalidate() in constructor solves the problem. However, I still am not seeing the renders on-screen that draw is supposedly doing. Is there something wrong with the arrayAdatper? :

@Override
    public View getView(int position, View convertView, ViewGroup parent){
        View rowView = convertView;
        //if data already exists in list reuse the data rather than re inflate from scratch
        if(rowView == null) {
            LayoutInflater inflater;
            inflater = LayoutInflater.from(context);

            rowView = inflater.inflate(resource, parent, false);
        }
        return rowView;
    }

Answer 1

call method invalidate() it will call onDraw() implicitly