Question

I have a application where i want to generate dots like 2 x 2, 3 x 3 and 4 x 4 dynamically

now i am drawing dot matrix without dynamic using code as follows :

if(test.equals("galmenu2"))
            {
            canvas.drawCircle(wid/4,3*ht/8,3, mPaint);
            canvas.drawCircle(3*wid/4,3*ht/8,3, mPaint);
            canvas.drawCircle(3*wid/4,5*ht/8,3, mPaint);
            canvas.drawCircle(wid/4,5*ht/8,3, mPaint);
            }
            else if(test.equals("galmenu3"))
            {
                canvas.drawCircle(wid/4,3*ht/8,3, mPaint);
                canvas.drawCircle(wid/2,3*ht/8,3, mPaint);
                canvas.drawCircle(3*wid/4,3*ht/8,3, mPaint);
                canvas.drawCircle(wid/4,ht/2,3, mPaint);
                canvas.drawCircle(wid/2,ht/2,3, mPaint);
                canvas.drawCircle(3*wid/4,ht/2,3, mPaint);

                canvas.drawCircle(wid/4,5*ht/8,3, mPaint);
                canvas.drawCircle(wid/2,5*ht/8,3, mPaint);
                canvas.drawCircle(3*wid/4,5*ht/8,3, mPaint);

            }
            else if(test.equals("galmenu4"))
            {
                for(wid=1/8;wid<1;wid+=2/8)
                {
                for(ht=5/16;ht<3/4;ht+=1/8)
                {
                    canvas.drawCircle(wid,ht,3, mPaint);
                }
                }//this for loop crash the application 
            }

and i need a formula to generate dots in my center of canvas please help me
The code mentioned above is added in onDraw() method Thanks in advance

Answer 1

To draw n by n circles on the canvas, I’d use the following:

// n is defined
for (int i=0; i<n; i++) {
    for (int j=0; j<n; j++) {
         canvas.drawCircle(((float)i +.5)/n*(float)width, ((float)j +.5)/n*(float)width, 3, mPaint);
     }
}

What is happening here?
We loop through n*n drawing commands:

• Draw at (i+.5)/n, which is a number between 0 and 1, which is the percentage of the width of the canaws where our coordinate is.
• Multiply it by the width to get the actual pixel coordinate
• Do the same with the height.
• Notice the (float) casts, which are needed to make sure the percentage is not rounded as an int.