Question

I’m very very new to android & JAVA, and I’m trying to learn writing android apps by myself. I met a problem when I was trying to read values from a csv file and plot them out. To be more specific, I was trying to modify Androidplot example.

The original Androidplot example works, while my modified one never work…I tried to find the problem but I failed failed failed…Every time I tried to debug the codes, ActivityThread.java just pops out, and there’s a little arrow pointing to the following codes:

catch (Exception e) {
        if (!mInstrumentation.onException(activity, e)) {
            throw new RuntimeException(
                "Unable to start activity " + component
                + ": " + e.toString(), e);
        }
    }

Can anybody tell me what the problem really is? Any help will be much appreciated =)

Below is my modified codes:

package edu.ius.rwisman.AndroidPlotExample;

import android.app.Activity;  

import android.graphics.Color;
import android.os.Bundle;
import com.androidplot.xy.SimpleXYSeries;
import com.androidplot.series.XYSeries;
import com.androidplot.xy.*;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.Arrays;


public class AndroidPlotExampleActivity extends Activity
{

private XYPlot mySimpleXYPlot;

@SuppressWarnings("null")
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    // Initialize our XYPlot reference:
    mySimpleXYPlot = (XYPlot) findViewById(R.id.mySimpleXYPlot);
    Number[] series1Numbers = null;
    Number[] series2Numbers = null;
    int row = 0;
    // Create two arrays of y-values to plot:
    try {

        File file = new File("/home/hanrui/workspace/table.csv");
        BufferedReader reader = new BufferedReader(new FileReader(file));
        reader.readLine();
        String line = null;
        while((line=reader.readLine())!=null&&row<24){
            String item[] = line.split(",");

            String last = item[item.length-1];
            int value = Integer.parseInt(last);
            series1Numbers[row] = value;
            series2Numbers[row] = value;
            row++;
        }
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }



    // Turn the above arrays into XYSeries:
    XYSeries series1 = new SimpleXYSeries(
            Arrays.asList(series1Numbers),          // SimpleXYSeries takes a List so turn our array into a List
            SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, // Y_VALS_ONLY means use the element index as the x value
            "Series1");                             // Set the display title of the series

    // Same as above, for series2
    XYSeries series2 = new SimpleXYSeries(Arrays.asList(series2Numbers), SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, 
            "Series2");

    // Create a formatter to use for drawing a series using LineAndPointRenderer:
    LineAndPointFormatter series1Format = new LineAndPointFormatter(
            Color.rgb(0, 200, 0),                   // line color
            Color.rgb(0, 100, 0),                   // point color
            Color.rgb(150, 190, 150));              // fill color (optional)

    // Add series1 to the xyplot:
    mySimpleXYPlot.addSeries(series1, series1Format);

    // Same as above, with series2:
    mySimpleXYPlot.addSeries(series2, new LineAndPointFormatter(Color.rgb(0, 0, 200), Color.rgb(0, 0, 100),
            Color.rgb(150, 150, 190)));


    // Reduce the number of range labels
    mySimpleXYPlot.setTicksPerRangeLabel(3);

    // By default, AndroidPlot displays developer guides to aid in laying out your plot.
    // To get rid of them call disableAllMarkup():
    mySimpleXYPlot.disableAllMarkup();
}
}

Answer 1

When running an Android application it is run on the phone (emulator or an actual device in itself) and thus this file will most likely not be found:

File file = new File("/home/hanrui/workspace/table.csv");

After your try-catch-statement, check to see if series1Numbers equals null.

Edit:

I noticed something, you’re never initializing your array of Number:

Number[] series1Numbers = null;.

Java isn’t PHP, in PHP the array would be created directly but in Java this is not the case. You need to call series1Numbers = new Number[10]; where 10 is the size of the array. I do recommend using ArrayList instead, as that can have a dynamical size.