Draw Text inside an Arc using canvas

Question

I am working in an android application to draw a circle and divide them equally and bind text inside the divided portion in the circle(like pichart). I have drawn a circle and divided them equally, but I want to bind text inside the divided portion. Please look into my code and give a solution. Thanks in advance.

public class MainActivity extends Activity {
    /** Called when the activity is first created. */
    float values[] = { 130, 130, 130, 130, 130 };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        LinearLayout linear = (LinearLayout) findViewById(R.id.linearlay);
        values = calculateData(values);
        linear.addView(new MyGraphview(this, values));
    }

    private float[] calculateData(float[] data) {

        float total = 0;
        for (int i = 0; i < data.length; i++) {
            total += data[i];
        }
        for (int i = 0; i < data.length; i++) {
            data[i] = 360 * (data[i] / total);
        }
        return data;

    }

    public class MyGraphview extends View {

        private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);     
        private float[] value_degree;
        private int[] COLORS = { Color.YELLOW, Color.GREEN, Color.WHITE,
                Color.CYAN, Color.RED };
        RectF rectf = new RectF(10, 10, 300, 300);
        Rect rect = new Rect(10, 10, 300, 300);
        int temp = 0;
        String rotatedtext;
        Path path;

        public MyGraphview(Context context, float[] values) {
            super(context);
            path = new Path();
            value_degree = new float[values.length];
            for (int i = 0; i < values.length; i++) {
                value_degree[i] = values[i];
            }

            paint.setTextSize(16);
            rotatedtext = "Rotated  :)";
        }

        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);

            for (int i = 0; i < value_degree.length; i++) {
                if (i == 0) {

                    paint.setColor(COLORS[i]);
                    canvas.drawArc(rectf, 0, value_degree[i], true, paint);

                } else {

                    temp += (int) value_degree[i - 1];
                    paint.setColor(COLORS[i]);
                    canvas.drawArc(rectf, temp, value_degree[i], true, paint); //

                }
            }

        }

    }
}

Answer 1

Try this:

private String[] STRINGS = { "Yellow", "GREEN", "WHITE", "CYAN", "RED" }; // Array of strings, just for the sample

    @Override
    protected void onDraw(Canvas canvas) 
    {           
        super.onDraw(canvas);

        temp = 0;

        int centerX = (rect.left + rect.right) / 2;
        int centerY = (rect.top + rect.bottom) / 2;
        int radius = (rect.right - rect.left) / 2;

        radius *= 0.5; // 1 will put the text in the border, 0 will put the text in the center. Play with this to set the distance of your text.

        for (int i = 0; i < data.length; i++) 
        {
            if (i > 0) 
                temp += (int) data[i - 1]; // rewrote your code here a bit, to avoid duplicate code.

            paint.setColor(COLORS[i]);
            canvas.drawArc(rectf, temp, data[i], true, paint);

            paint.setColor(Color.BLACK); // set this to the text color.
            float medianAngle = (temp + (data[i] / 2f)) * (float)Math.PI / 180f; // this angle will place the text in the center of the arc.
            canvas.drawText(STRINGS[i], (float)(centerX + (radius * Math.cos(medianAngle))), (float)(centerY + (radius * Math.sin(medianAngle))), paint);
        }
    }

Also, for nicer results, make sure to set the Align.CENTER property in the paint before drawing any text:

paint.setTextSize(16);
paint.setTextAlign(Align.CENTER);

Hope this helps :)