achart 예제를 보고 따라했는데 올리면 경고창 뜨네요 ㅠㅠ

아래 모가 문제 일까요 ?; 부탁드립니다.

package c.c.PieChart;

import org.achartengine.ChartFactory;
import org.achartengine.model.CategorySeries;
import org.achartengine.renderer.DefaultRenderer;
import org.achartengine.renderer.SimpleSeriesRenderer;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;

public class PieChart extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
       
        Intent achartIntent = new AChartExample().execute(this);
        startActivity(achartIntent);
       
    }
    public class AChartExample {  
     public Intent execute(Context context) {
      int[] colors = new int[] { Color.RED, Color.YELLOW, Color.BLUE };
      DefaultRenderer renderer = buildCategoryRenderer(colors);  
      CategorySeries categorySeries = new CategorySeries("Vehicles Chart");
      categorySeries.add("cars ", 30);
      categorySeries.add("trucks", 20);
      categorySeries.add("bikes ", 60);  
      return ChartFactory.getPieChartIntent(context, categorySeries, renderer);
      }  
     protected DefaultRenderer buildCategoryRenderer(int[] colors) {
      DefaultRenderer renderer = new DefaultRenderer();
      for (int color : colors) {
       SimpleSeriesRenderer r = new SimpleSeriesRenderer();
       r.setColor(color); renderer.addSeriesRenderer(r);
      }
      return renderer;
     }
   }
}