com.google.gwt.graphics.client.charts.PieChart.java Source code

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Here is the source code for com.google.gwt.graphics.client.charts.PieChart.java

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/*
 * Copyright 2009 Google Inc.
 * 
 * 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.google.gwt.graphics.client.charts;

import com.google.gwt.graphics.client.Canvas;
import com.google.gwt.graphics.client.Color;
import com.google.gwt.resources.client.CssResource;
import com.google.gwt.topspin.ui.client.Container;
import com.google.gwt.topspin.ui.client.DefaultContainerImpl;
import com.google.gwt.topspin.ui.client.Widget;

import java.util.List;

/**
 * A pie chart!
 */
public class PieChart extends SimpleChart {
    /**
     * Legend styles.
     */
    public interface Css extends CssResource {
        String legend();

        String pieChart();
    }

    /**
     * Resources interface.
     */
    public interface Resources extends Legend.Resources {
        @Source("resources/PieChart.css")
        PieChart.Css pieChartCss();
    }

    private static final int COORD_RADIUS = 50;
    private static final int PADDING = 10;
    private static final int CANVAS_COORD_SIZE = COORD_RADIUS * 2 + PADDING;

    private final Canvas canvas;
    private Legend legend;
    private final PieChart.Resources resources;

    public PieChart(Container container, List<ColorCodedValue> data, PieChart.Resources resources) {
        super(container, data);
        // We want our wrapping container to size to the contents.
        getElement().getStyle().setProperty("display", "inline-block");
        this.resources = resources;
        canvas = new Canvas(CANVAS_COORD_SIZE, CANVAS_COORD_SIZE);
        getElement().appendChild(canvas.getElement());
        canvas.getElement().setClassName(resources.pieChartCss().pieChart());
        canvas.setStrokeStyle(Color.MIDNIGHT_BLUE);
        canvas.setLineWidth(1.0);

        render();
    }

    public PieChart(Widget parent, List<ColorCodedValue> data, PieChart.Resources resources) {
        this(new DefaultContainerImpl(parent.getElement()), data, resources);
    }

    @Override
    public void render() {
        canvas.clear();
        double lastAngle = 0;
        double center = CANVAS_COORD_SIZE / 2;
        List<ColorCodedValue> data = getData();
        // Draw pie chart
        for (int i = 0, n = data.size(); i < n; i++) {
            ColorCodedValue entry = data.get(i);
            canvas.setFillStyle(entry.labelColor);
            double arcFraction = entry.value / getDataTotal();
            double arcAngle = Math.PI * 2 * arcFraction;
            double newAngle = lastAngle + arcAngle;
            canvas.beginPath();
            canvas.moveTo(center, center);
            canvas.arc(center, center, COORD_RADIUS, lastAngle, newAngle, false);
            canvas.fill();
            canvas.stroke();
            lastAngle = newAngle;
        }
    }

    public void resize(int width, int height) {
        canvas.resize(width, height);
    }

    @Override
    public void setData(List<ColorCodedValue> data) {
        super.setData(data);
        if (legend != null) {
            // It has been queried before and is already attached to us.
            boolean wasVisible = legend.isVisible();

            legend.destroy();
            legend = null;

            // Redisplay if needed. We invoke the hide/show methods and not simply
            // setVisible() because they call ensureLegend() first.
            if (wasVisible) {
                showLegend();
            } else {
                hideLegend();
            }
        }
    }

    @Override
    protected Legend getLegend() {
        ensureLegend();
        return legend;
    }

    private void ensureLegend() {
        if (legend == null) {
            legend = new Legend(this, getData(), getDataTotal(), false, true, resources);
            legend.getElement().setClassName(resources.pieChartCss().legend());
        }
    }
}