RangeGraph.java

package com.example.rangegraph;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.FontMetrics;
import android.graphics.Paint.Style;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

/**
 * Draw a Range Graph to show if the current value is in range or not
 * Example AsciiArt:<pre>
 *     | T |
 *     | T |
 * 140 | M |
 *     | M |
 * 120 | B |
 *     | B |
 * </pre>
 * The region T will be red if the value is too high, blank otherwise
 * The region M will be red if the value is out of range, green otherwise
 * The region B will be red if the value is too low, green otherwise
 * @author Ian Darwin
 */
public class RangeGraph extends View {

	private static final String TAG = "RangeGraph";
	
	// State
	private int mMin = 0, mMax = 100;
	private int mValue = 50;
	
	// Graphics
	protected int colorNeutral = Color.BLACK;
	protected int colorOutOfRange = Color.RED;
	protected int colorInRange = Color.GREEN;
	private int mFontSize = 16;
	private Paint mPaint;
    
	// Layout
	private int mWidth = 200;
	private int mHeight = 300;

	public RangeGraph(Context context) {
		super(context);
		commonSetup();
	}

	/**
	 * @param context
	 * @param attrs
	 */
	public RangeGraph(Context context, AttributeSet attrs) {
		super(context, attrs);
				
		// Then allow overrides from XML
		TypedArray a = context.getTheme().obtainStyledAttributes(
				attrs,
				R.styleable.RangeGraph,
				0, 0);

		try {
			colorNeutral = a.getColor(R.styleable.RangeGraph_colorNeutral, Color.BLACK);
			colorInRange = a.getColor(R.styleable.RangeGraph_colorInRange, Color.GREEN);
			colorOutOfRange = a.getColor(R.styleable.RangeGraph_colorOutOfRange, Color.RED);
			mMin = a.getInteger(R.styleable.RangeGraph_minimum, 0);
			mMax = a.getInteger(R.styleable.RangeGraph_maximum, 100);
		} finally {
			a.recycle();
		}

		commonSetup();
	}
	
	private void commonSetup() {

		mPaint = new Paint();
		mPaint.setColor(colorNeutral);
		// Scale the desired text size to match screen density
        mPaint.setTextSize(mFontSize * getResources().getDisplayMetrics().density);
		mPaint.setStrokeWidth(2f);
        setPadding(5, 5, 5, 5);
	}
	
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		setMeasuredDimension(mWidth, mHeight);
	}
	
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		
		// Label it
		int oneThirdHeight = getPaddingTop() + (2*mHeight/3);
        int twoThirdsHeight = getPaddingTop() + (mHeight/3);
        
        String stringMax = Integer.toString(mMax);
        String stringMin = Integer.toString(mMin);
        String stringValue = Integer.toString(mValue);
		FontMetrics fm = mPaint.getFontMetrics();
		final float fontHeight = fm.ascent + fm.descent;
		
		canvas.drawText(stringMax, 
        		getPaddingLeft(), twoThirdsHeight - fontHeight/2, mPaint);
		canvas.drawText(stringMin, 
        		getPaddingLeft(), oneThirdHeight - (fontHeight/2), mPaint);
        
        // Draw the bar outline, at 1/2 and 2/3 of the width
        int top = getPaddingTop();
        int bot = mHeight - getPaddingBottom();
        int leftSide = (int) (mWidth*0.40f);
        int rightSide = (int) (mWidth*0.60f);
        Style oldStyle = mPaint.getStyle();
        mPaint.setStyle(Paint.Style.STROKE);
        canvas.drawRect(leftSide, top, rightSide, bot, mPaint);
        mPaint.setStyle(oldStyle);
		
		// Now draw the bar graph.
		// The distance from min to max fills the middle third of the graph
		int oneThirdValue = mMax - mMin;
		int valueRange = oneThirdValue * 3;
		int valueAtBottom = mMin - oneThirdValue;
		int visibleValue = Math.max(0, mValue - valueAtBottom);
		int barHeight = Math.min(mHeight, (int) (mHeight * (1f * visibleValue / valueRange)));
		
		// First put in three tick marks before changing the color
		canvas.drawLine(leftSide-20, oneThirdHeight, leftSide, oneThirdHeight, mPaint);
		canvas.drawLine(leftSide-20, twoThirdsHeight, leftSide, twoThirdsHeight, mPaint);
		canvas.drawLine(rightSide, mHeight - barHeight, rightSide + 20, mHeight - barHeight, mPaint);
		
		mPaint.setColor(isInRange() ? colorInRange : colorOutOfRange);
		Log.d(TAG,
			String.format("drawRect(%d %d %d %d)",
					leftSide, mHeight - barHeight, rightSide, bot));
		canvas.drawRect(leftSide, mHeight - barHeight, rightSide, bot, mPaint);
		
		// Draw the actual reading beside the bar top
		mPaint.setColor(isInRange() ? colorNeutral : colorOutOfRange);
		canvas.drawText(stringValue, 
				mWidth*0.65f, mHeight - barHeight - (fontHeight/2), mPaint);
	}

	public boolean isInRange() {
		return mValue >= mMin && mValue <= mMax;
	}
	
	// Simple accessors
	
	public int getMin() {
		return mMin;
	}
	public void setMin(int min) {
		this.mMin = min;
	}
	public int getMax() {
		return mMax;
	}
	public void setMax(int max) {
		this.mMax = max;
	}
	public int getValue() {
		return mValue;
	}
	public void setValue(int value) {
		this.mValue = value;
	}

	public int getColorOutOfRange() {
		return colorOutOfRange;
	}

	public void setColorOutOfRange(int colorOutOfRange) {
		this.colorOutOfRange = colorOutOfRange;
	}

	public int getColorInRange() {
		return colorInRange;
	}

	public void setColorInRange(int colorInRange) {
		this.colorInRange = colorInRange;
	}

	public int getColorNeutral() {
		return colorNeutral;
	}

	public void setColorNeutral(int colorNeutral) {
		this.colorNeutral = colorNeutral;
	}
	
}