2D Array grid on drawing canvas

public class PixelGridView extends View {


//number of row and column 

    int horizontalGridCount = 2;


    private Drawable horiz;
    private Drawable vert;
    private final float width;



    public PixelGridView(@NonNull Context context) {
        this(context, null);
    }

    public PixelGridView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        horiz = new ColorDrawable(Color.WHITE); horiz.setAlpha(160);
        vert = new ColorDrawable(Color.WHITE); vert.setAlpha(160);
        width = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 0.9f, context.getResources().getDisplayMetrics());
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        horiz.setBounds(left, 0, right, (int) width);
        vert.setBounds(0, top, (int) width, bottom);
    }





    private float getLinePosition(int lineNumber) {
        int lineCount = horizontalGridCount;

            return (1f / (lineCount + 1)) * (lineNumber + 1f);

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
       // drawTask.start();
        int count = horizontalGridCount;
        for (int n = 0; n < count; n++) {
            float pos = getLinePosition(n);

            // Draw horizontal line
            canvas.translate(0, pos * getHeight());
            horiz.draw(canvas);
            canvas.translate(0, - pos * getHeight());

            // Draw vertical line
            canvas.translate(pos * getWidth(), 0);
            vert.draw(canvas);
            canvas.translate(- pos * getWidth(), 0);
        }
        //drawTask.end(count);
    }
}

and in your main activity:

//inside on create method

        val myView = PixelGridView(this)

        id_frame.addView(myView)

id_frame is frame layout in xml

The following is just a simple, illustrative example. It is not optimized, implements no exception handling, etc.

public class PixelGridView extends View {
    private int numColumns, numRows;
    private int cellWidth, cellHeight;
    private Paint blackPaint = new Paint();
    private boolean[][] cellChecked;

    public PixelGridView(Context context) {
        this(context, null);
    }

    public PixelGridView(Context context, AttributeSet attrs) {
        super(context, attrs);
        blackPaint.setStyle(Paint.Style.FILL_AND_STROKE);
    }

    public void setNumColumns(int numColumns) {
        this.numColumns = numColumns;
        calculateDimensions();
    }

    public int getNumColumns() {
        return numColumns;
    }

    public void setNumRows(int numRows) {
        this.numRows = numRows;
        calculateDimensions();
    }

    public int getNumRows() {
        return numRows;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        calculateDimensions();
    }

    private void calculateDimensions() {
        if (numColumns < 1 || numRows < 1) {
            return;
        }

        cellWidth = getWidth() / numColumns;
        cellHeight = getHeight() / numRows;

        cellChecked = new boolean[numColumns][numRows];

        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawColor(Color.WHITE);

        if (numColumns == 0 || numRows == 0) {
            return;
        }

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

        for (int i = 0; i < numColumns; i++) {
            for (int j = 0; j < numRows; j++) {
                if (cellChecked[i][j]) {

                    canvas.drawRect(i * cellWidth, j * cellHeight,
                                    (i + 1) * cellWidth, (j + 1) * cellHeight,
                                    blackPaint);
                }
            }
        }

        for (int i = 1; i < numColumns; i++) {
            canvas.drawLine(i * cellWidth, 0, i * cellWidth, height, blackPaint);
        }

        for (int i = 1; i < numRows; i++) {
            canvas.drawLine(0, i * cellHeight, width, i * cellHeight, blackPaint);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            int column = (int)(event.getX() / cellWidth);
            int row = (int)(event.getY() / cellHeight);

            cellChecked[column][row] = !cellChecked[column][row];
            invalidate();
        }

        return true;
    }
}

Here's a simple Activity for demonstration:

public class MainActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        PixelGridView pixelGrid = new PixelGridView(this);
        pixelGrid.setNumColumns(4);
        pixelGrid.setNumRows(6);

        setContentView(pixelGrid);
    }
}