androidplot/pie/PieRenderer.java

/*
 * Copyright 2013 AndroidPlot.com
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

package com.androidplot.pie;

import android.graphics.*;

import com.androidplot.exception.PlotRenderException;
import com.androidplot.ui.SeriesRenderer;

import java.util.Set;

public class PieRenderer extends SeriesRenderer<PieChart, Segment, SegmentFormatter> {

    // starting angle to use when drawing the first radial line of the first segment.
    @SuppressWarnings("FieldCanBeLocal")
    private float startDeg = 0;
    private float endDeg = 360;

    // TODO: express donut in units other than px.
    private float donutSize = 0.5f;
    private DonutMode donutMode = DonutMode.PERCENT;

    public enum DonutMode {
        PERCENT,
        DP,
        PIXELS
    }

    public PieRenderer(PieChart plot) {
        super(plot);
    }

    public float getRadius(RectF rect) {
    	return  rect.width() < rect.height() ? rect.width() / 2 : rect.height() / 2;
    }

    @Override
    public void onRender(Canvas canvas, RectF plotArea) throws PlotRenderException {

        float radius = getRadius(plotArea);
        PointF origin = new PointF(plotArea.centerX(), plotArea.centerY());

        double[] values = getValues();
        double scale = calculateScale(values);
        float offset = startDeg;
        Set<Segment> segments = getPlot().getSeriesSet();

        //PointF lastRadial = calculateLineEnd(origin, radius, offset);

        RectF rec = new RectF(origin.x - radius, origin.y - radius, origin.x + radius, origin.y + radius);

        int i = 0;
        for (Segment segment : segments) {
            float lastOffset = offset;
            float sweep = (float) (scale * (values[i]) * 360);
            offset += sweep;
            //PointF radial = calculateLineEnd(origin, radius, offset);
            drawSegment(canvas, rec, segment, getPlot().getFormatter(segment, PieRenderer.class),
                    radius, lastOffset, sweep);
            //lastRadial = radial;
            i++;
        }
    }

    protected void drawSegment(Canvas canvas, RectF bounds, Segment seg, SegmentFormatter f,
                               float rad, float startAngle, float sweep) {
        canvas.save();

        float cx = bounds.centerX();
        float cy = bounds.centerY();

        float donutSizePx;
        switch(donutMode) {
            case PERCENT:
                donutSizePx = donutSize * rad;
                break;
            case PIXELS:
                donutSizePx = (donutSize > 0)?donutSize:(rad + donutSize);
                break;
            default:
                throw new UnsupportedOperationException("Not yet implemented.");
        }

        // vertices of the first radial:
        PointF r1Outer = calculateLineEnd(cx, cy, rad, startAngle);
        PointF r1Inner = calculateLineEnd(cx, cy, donutSizePx, startAngle);

        // vertices of the second radial:
        PointF r2Outer = calculateLineEnd(cx, cy, rad, startAngle + sweep);
        PointF r2Inner = calculateLineEnd(cx, cy, donutSizePx, startAngle + sweep);

        Path clip = new Path();

        //float outerStroke = f.getOuterEdgePaint().getStrokeWidth();
        //float halfOuterStroke = outerStroke / 2;

        // leave plenty of room on the outside for stroked borders;
        // necessary because the clipping border is ugly
        // and cannot be easily anti aliased.  Really we only care about masking off the
        // radial edges.
        clip.arcTo(new RectF(bounds.left - rad,
                bounds.top - rad,
                bounds.right + rad,
                bounds.bottom + rad),
                startAngle, sweep);
        clip.lineTo(cx, cy);
        clip.close();
        canvas.clipPath(clip);

        Path p = new Path();
        p.arcTo(bounds, startAngle, sweep);
        p.lineTo(r2Inner.x, r2Inner.y);

        // sweep back to original angle:
        p.arcTo(new RectF(
                cx - donutSizePx,
                cy - donutSizePx,
                cx + donutSizePx,
                cy + donutSizePx),
                startAngle + sweep, -sweep);

        p.close();

        // fill segment:
        canvas.drawPath(p, f.getFillPaint());

        // draw radial lines
        canvas.drawLine(r1Inner.x, r1Inner.y, r1Outer.x, r1Outer.y, f.getRadialEdgePaint());
        canvas.drawLine(r2Inner.x, r2Inner.y, r2Outer.x, r2Outer.y, f.getRadialEdgePaint());

        // draw inner line:
        canvas.drawCircle(cx, cy, donutSizePx, f.getInnerEdgePaint());

        // draw outer line:
        canvas.drawCircle(cx, cy, rad, f.getOuterEdgePaint());
        canvas.restore();

        PointF labelOrigin = calculateLineEnd(cx, cy,
                (rad-((rad- donutSizePx)/2)), startAngle + (sweep/2));

        // TODO: move segment labelling outside the segment drawing loop
        // TODO: so that the labels will not be clipped by the edge of the next
        // TODO: segment being drawn.
        drawSegmentLabel(canvas, labelOrigin, seg, f);
    }

    protected void drawSegmentLabel(Canvas canvas, PointF origin,
                                    Segment seg, SegmentFormatter f) {
        canvas.drawText(seg.getTitle(), origin.x, origin.y, f.getLabelPaint());

    }

    @Override
    protected void doDrawLegendIcon(Canvas canvas, RectF rect, SegmentFormatter formatter) {
        throw new UnsupportedOperationException("Not yet implemented.");
    }

    /**
     * Determines how many counts there are per cent of whatever the
     * pie chart is displaying as a fraction, 1 being 100%.
     */
    private double calculateScale(double[] values) {
        double total = 0;
        for (int i = 0; i < values.length; i++) {
			total += values[i];
		}

        return (1d / total);
    }

	private double[] getValues() {
		Set<Segment> segments = getPlot().getSeriesSet();
		double[] result = new double[segments.size()];
		int i = 0;
		for (Segment seg : getPlot().getSeriesSet()) {
			result[i] = seg.getValue().doubleValue();
			i++;
		}
		return result;
	}

    private PointF calculateLineEnd(float x, float y, float rad, float deg) {
        return calculateLineEnd(new PointF(x, y), rad, deg);
    }

    private PointF calculateLineEnd(PointF origin, float rad, float deg) {

        double radians = deg * Math.PI / 180F;
        double x = rad * Math.cos(radians);
        double y = rad * Math.sin(radians);

        // convert to screen space:
        return new PointF(origin.x + (float) x, origin.y + (float) y);
    }

    public void setDonutSize(float size, DonutMode mode) {
        switch(mode) {
            case PERCENT:
                if(size < 0 || size > 1) {
                    throw new IllegalArgumentException(
                            "Size parameter must be between 0 and 1 when operating in PERCENT mode.");
                }
                break;
            case PIXELS:
            	break;
            default:
                throw new UnsupportedOperationException("Not yet implemented.");
        }
        donutMode = mode;
        donutSize = size;
    }

    public void setStartDeg(float deg) {
        startDeg = deg;
    }

    public void setEndDeg(float deg) {
        endDeg = deg;
    }
}