GraphDrawer

package com.int

import net.astesana.javaluator.DoubleEvaluator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Point;
import android.util.DisplayMetrics;
import android.view.Display;
import android.view.View;
import android.view.WindowManager;

public class GraphDrawer extends View {

    // My paint brushes
    Paint axis = new Paint();
    Paint axisNumbers = new Paint();
    Paint graph1 = new Paint();
    Paint graph2 = new Paint();
    Paint extremal = new Paint();


    // Get screen size from users mobile phone/tablet
    DisplayMetrics dm = new DisplayMetrics();
    int width = getContext().getResources().getDisplayMetrics().widthPixels;
    int height = getContext().getResources().getDisplayMetrics().heightPixels;

    // Get from user
    double xMin = -10.0;
    double xMax = 10.0;
    double xScale = 1.0;
    double yMin = -10.0;
    double yMax = 10.0;
    double yScale = 1.0;

    // Get equation from user
    public String e1 = "(Some equation from Graph.java)";


    public GraphDrawer(Context context) {
        super(context);

        // Set axes colors
        axis.setColor(Color.rgb(164, 164, 164)); // light grey
        axisNumbers.setColor(Color.rgb(65, 65, 65)); // dark grey
        axisNumbers.setTextSize(16);

        // Set graph colors
        graph1.setColor(Color.rgb(82, 85, 164));
        graph2.setColor(Color.rgb(82, 85, 164));

        // Set extremal colors
        extremal.setColor(Color.rgb(0,0,0));
        extremal.setTextSize(20);
    }

    @Override
    public void onDraw(Canvas canvas) {
        /*- Calcualte what is largest, x or y? to find plot size ------------------------ */
        int p; // plotSize
        if(width < height){
            p = width;
        }
        else{
            p = height;
        }



        /*- Draw y axis ------------------------------------------------------------------ */
        // Draw y axes
        canvas.drawLine(p/2, 0, p/2, p, axis); // startX, startY, stopX, stopY

        // Draw horizontal lines on y axis
        double yPlacement = 0;
        int yPlacementInt;

        double yMinAbs = Math.abs(yMin); // How many points are there between yMin and yMax?
        double yMaxAbs = Math.abs(yMax);
        double yQuantity = yMinAbs+yMaxAbs;
        double heightDividedByNumberOfPixels = p/yQuantity;

        for(double i=yMin;i<yMax;i++){

            // Line
            yPlacement = yPlacement+heightDividedByNumberOfPixels;
            yPlacementInt = (int)yPlacement;
            canvas.drawLine((width/2)-6, yPlacementInt, (width/2)+6, yPlacementInt, axis); // startX, startY, stopX, stopY

            // Scale
            i = i-1+yScale;
        } // for


        /*- Draw x axis ------------------------------------------------------------------ */
        canvas.drawLine(0, p/2, p, p/2, axis); // startX, startY, stopX, stopY

        // Draw vertical lines on x axis
        double xPlacement = 0;
        int xPlacementInt;

        double xMinAbs = Math.abs(xMin); // How many points are there between yMin and yMax?
        double xMaxAbs = Math.abs(xMax);
        double xQuantity = xMinAbs+xMaxAbs;
        double xWidthDividedByNumberOfPixels = p/xQuantity;

        for(double i=xMin;i<xMax;i++){

            // Line
            xPlacement = xPlacement+xWidthDividedByNumberOfPixels;
            xPlacementInt = (int)xPlacement;
            canvas.drawLine(xPlacementInt, (width/2)-6, xPlacementInt, (width/2)+6, axis); // startX, startY, stopX, stopY

            // Scale
            i = i-1+xScale;
        }



        /*- Draw Equation 1 ------------------------------------------------------------- */
        double xValueD = xMin;
        String xValueS;
        int xValueI;

        double yValueD = 0;
        String yValueS;
        int yValueI;

        String expression;

        // What size is one square?
        yMinAbs = Math.abs(yMin); // How many points are there between yMin and yMax?
        yMaxAbs = Math.abs(yMax);
        yQuantity = yMinAbs+yMaxAbs;
        double route = p/yQuantity;

        // Temporary double values
        double xCord = 0.0;
        double yCord = 0.0;

        //
        double a;

        for(double i=0;i<5000;i++){

                // Find next x value
                xValueD = xValueD+0.001;
                xValueD = xValueD*1000;
                xValueD = Math.round(xValueD);
                xValueD = xValueD/1000;
                xValueS = Double.toString(xValueD);
                if(xValueD < 0.0){
                    xValueS = "(" + xValueS + ")";
                }

                expression = e1.replaceAll("x",xValueS);

                try{
                    yValueD = new DoubleEvaluator().evaluate(expression);

                    // Calculate where the dot should be placed


                    // x cord
                    xCord = 240+xValueD*24;

                    // y cord
                    yCord = 240+yValueD*-24;

                    int startX = (int)(xCord);
                    int startY = (int)(yCord);
                    int stopX = (int)(xCord);
                    int stopY = (int)(yCord);

                    // Draw it
                    if(startX < p && startY < p){
                        canvas.drawLine(startX, startY, stopX+1, stopY, graph1); // startX, startY, stopX, stopY
                    }
                    else{
                        // we are out of range, plus 1 extra to xvalue
                        xValueD = xValueD+0.5;
                    }


                }
                catch (Exception e) {
                    String errorMsg = "Error: " + e;

                    // canvas.drawText(errorMsg, -150, 20, axisNumbers);
                    // canvas.drawText(expression, 0, 40, axisNumbers);
                }
        }


    }

    public void putExtra(String tempDataEditTextEquation1) {
        e1 = tempDataEditTextEquation;
    }

}