Histogram.java

package uk.org.smithfamily.mslogger.widgets.renderers;

import uk.org.smithfamily.mslogger.dashboards.DashboardView;
import uk.org.smithfamily.mslogger.widgets.Indicator;
import uk.org.smithfamily.mslogger.widgets.Indicator.DisplayType;
import android.content.Context;
import android.graphics.*;

public class Histogram extends Painter
{
    private Paint backgroundPaint;
    private Paint linePaint;
    private Paint valuePaint;
    private RectF borderRect;
    private static final int NB_VALUES = 100;
    private final float[] values = new float[NB_VALUES];

    private int indexValue = 0;
    private Path linePath;
    private int height;
    private int width;

    public Histogram(final DashboardView parent, final Indicator model, final Context c)
    {
        super(parent, model, c);
    }

    @Override
    protected void init(final Context c)
    {
        initDrawingTools(c);
    }

    /**
     * 
     * @param context
     */
    private void initDrawingTools(final Context context)
    {
        int anti_alias_flag = Paint.ANTI_ALIAS_FLAG;
        if (parent.isInEditMode())
        {
            anti_alias_flag = 0;
        }

        linePath = new Path();

        backgroundPaint = new Paint();
        backgroundPaint.setColor(Color.WHITE);
        backgroundPaint.setTextSize(0.06f);
        backgroundPaint.setTextAlign(Paint.Align.LEFT);
        backgroundPaint.setStyle(Paint.Style.STROKE);
        backgroundPaint.setFlags(anti_alias_flag);
        backgroundPaint.setAntiAlias(true);

        valuePaint = new Paint();
        valuePaint.setColor(Color.DKGRAY);
        valuePaint.setTextAlign(Paint.Align.RIGHT);
        valuePaint.setLinearText(true);
        valuePaint.setFlags(anti_alias_flag);
        valuePaint.setAntiAlias(true);

        linePaint = new Paint();
        linePaint.setColor(Color.BLUE);
        linePaint.setFlags(anti_alias_flag);
        linePaint.setAntiAlias(true);
        linePaint.setStyle(Paint.Style.STROKE);

        borderRect = new RectF();
        borderRect.set(0.05f, 0.05f, 0.94f, 0.83f);
    }

    /**
     * Add a value to display on the histogram
     * 
     * @param value
     */
    public void addValue(final double value)
    {
        values[indexValue] = (float) value;
        indexValue++;
        indexValue = indexValue % NB_VALUES;
    }

    /**
     * @param canvas
     */
    @Override
    public void renderFrame(final Canvas canvas)
    {
        height = (int) (bottom - top);
        width = (int) (right - left);

        if ((width == 0) || (height == 0))
        {// We're not ready to do this yet
            return;
        }

        canvas.save(Canvas.ALL_SAVE_FLAG);
        canvas.translate(left, top);
        canvas.clipRect(0, 0, width, height);

        backgroundPaint.setTextSize(0.06f * height);

        // canvas.scale(width, height);

        drawBackground(canvas);

        addValue(model.getValue());
        drawTitle(canvas);
        drawValue(canvas);
        drawLines(canvas);

        canvas.restore();
    }

    private void drawLines(final Canvas canvas)
    {
        linePath.reset();

        final double min = model.getMin();
        final double max = model.getMax();
        final double range = max - min;
        float x;
        float y;
        float value;
        int idx;
        final int numPoints = NB_VALUES - 1;
        for (int i = 0; i < numPoints; i++)
        {
            idx = (indexValue + i) % numPoints;
            value = values[idx];
            x = ((float) i / (float) numPoints) * width + 1;

            y = (float) (1.0f - ((value - min) / range)) * height;

            if (i == 0)
            {
                linePath.moveTo(x, y);
            }
            else
            {
                linePath.lineTo(x, y);
            }
        }
        canvas.drawPath(linePath, linePaint);
    }

    public void drawBackground(final Canvas canvas)
    {
        canvas.drawRect(0, 0, width, height, backgroundPaint);
    }

    public void drawValue(final Canvas canvas)
    {
        valuePaint.setColor(getFgColour());

        final double value = model.getValue();
        final int valueDigits = model.getVd();
        final float displayValue = (float) (Math.floor((value / Math.pow(10, -valueDigits)) + 0.5) * Math.pow(10, -valueDigits));

        String text;

        if (valueDigits <= 0)
        {
            text = Integer.toString((int) displayValue);
        }
        else
        {
            text = Float.toString(displayValue);
        }
        valuePaint.setTextSize(0.06f * height);
        canvas.drawText(text, 0.94f * width, 0.90f * height, valuePaint);
    }

    public void drawTitle(final Canvas canvas)
    {
        backgroundPaint.setColor(getFgColour());

        String text = model.getTitle();
        if (!model.getUnits().equals(""))
        {
            text += " (" + model.getUnits() + ")";
        }

        canvas.drawText(text, 0.05f * width, 0.90f * height, backgroundPaint);
    }

    @Override
    public DisplayType getType()
    {
        return DisplayType.HISTOGRAM;
    }

    @Override
    public boolean isIsotropic()
    {
        return false;
    }

    @Override
    public boolean updateAnimation()
    {
        // Histogram is not animated like a gauge so we just say we're good to go
        return false;
    }
}