Achartengine繪製額外的垃圾字符

我喜歡用於Android的achartengine圖表庫，但我一直在收到這個問題。我希望該活動能夠通過單擊按鈕重新繪製來自我的數據庫的不同數據集的圖表（返回不同的時間量）。在活動中有三個按鈕以及圖表（在包含圖表的列表視圖下方）。除了一些額外的垃圾字符被按下後，它們會在按鈕後面繪製。它不會在第一次按下按鈕時發生，而是在按下按鈕時（無所謂）垃圾出現。Achartengine繪製額外的垃圾字符

我的佈局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" > 

    <LinearLayout 
     android:id="@+id/chart" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:orientation="horizontal" 
     android:background="#000000"/> 

    <Button 
     android:id="@+id/oneMonth" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:layout_alignParentLeft="true" 
     android:layout_marginLeft="25dp" 
     android:text="@string/OneMonth" /> 

    <Button 
     android:id="@+id/twoMonth" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:layout_centerHorizontal="true" 
     android:text="@string/TwoMonth" /> 

    <Button 
     android:id="@+id/threeMonth" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:layout_alignParentRight="true" 
     android:layout_marginRight="25dp" 
     android:text="@string/ThreeMonth" /> 

</RelativeLayout>

我的活動：

import java.text.DateFormat; 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.ArrayList; 
import java.util.Date; 
import java.util.List; 

import org.achartengine.ChartFactory; 
import org.achartengine.GraphicalView; 
import org.achartengine.chart.PointStyle; 
import org.achartengine.model.TimeSeries; 
import org.achartengine.model.XYMultipleSeriesDataset; 
import org.achartengine.renderer.XYMultipleSeriesRenderer; 
import org.achartengine.renderer.XYSeriesRenderer; 
import android.app.Activity; 
import android.database.Cursor; 
import android.graphics.Color; 
import android.os.Bundle; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.LinearLayout; 
import android.widget.Toast; 

public class Plot extends Activity{ 

/** Called when the activity is first created. */ 
    private XYMultipleSeriesDataset mDataset; 
    private XYMultipleSeriesRenderer mRenderer; 
    List<double[]> values = new ArrayList<double[]>(); 
    private GraphicalView mChartView; 
    private TimeSeries time_series; 
    private final String RANGE = "range"; 
    LinearLayout layout; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 

     super.onCreate(savedInstanceState); 
     setContentView(R.layout.plot); 

     layout = (LinearLayout)findViewById(R.id.chart); 

     final Button set30 = (Button)findViewById(R.id.oneMonth); 
     final Button set60 = (Button)findViewById(R.id.twoMonth); 
     final Button set90 = (Button)findViewById(R.id.threeMonth); 

     set30.setOnClickListener(new OnClickListener(){ 

      @Override 
      public void onClick(View arg0) { 

       setUpChart(-30); 

      }}); 

     set60.setOnClickListener(new OnClickListener(){ 

      @Override 
      public void onClick(View arg0) { 

       setUpChart(-60); 

      }}); 



     set90.setOnClickListener(new OnClickListener(){ 

      @Override 
      public void onClick(View arg0) { 

       setUpChart(-90); 

      }}); 

     } 



    @Override 
    protected void onResume() { 

     super.onResume(); 
     setUpChart(-30); 
    } 

    private void fillData(int x) { 
     DataBaseHelper helper = new DataBaseHelper(this.getApplicationContext()); 
     helper.open(DataBaseHelper.READABLE); 

     Cursor cursor = helper.getDaysSoManyDaysInThePast(x); 

     if(cursor.getCount() != 0){ 
      DateFormat formatter ; 
      Date date = null; 
       formatter = new SimpleDateFormat(DataBaseHelper.DATE_FORMAT); 
      String s; 

      int dateCol = cursor.getColumnIndex("date"); 
      int caffCol = cursor.getColumnIndex("sum(mgCaffeine)"); 

      for(cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()){ 

       s = cursor.getString(dateCol); 
       try { 
        date = (Date)formatter.parse(s); 

       } catch (ParseException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
        Toast.makeText(this, e.getMessage(), Toast.LENGTH_SHORT).show(); 
       } 
       int caff = cursor.getInt(caffCol); 
       time_series.add(date, caff);    
      } 


     }else{ 
      Toast.makeText(this, "No data", Toast.LENGTH_SHORT).show(); 
     } 

     helper.close(); 
    } 

     private void setUpChart(int x){ 

      mDataset = new XYMultipleSeriesDataset(); 
      mRenderer = new XYMultipleSeriesRenderer(); 
      mRenderer.setAxisTitleTextSize(16); 
      mRenderer.setChartTitleTextSize(20); 
      mRenderer.setLabelsTextSize(15); 
      mRenderer.setLegendTextSize(20); 
      mRenderer.setPointSize(3f); 

      XYSeriesRenderer r = new XYSeriesRenderer(); 
      r.setColor(Color.GREEN); 
      r.setPointStyle(PointStyle.CIRCLE); 
      r.setFillPoints(true); 
      mRenderer.addSeriesRenderer(r); 
      mRenderer.setClickEnabled(true); 
      mRenderer.setSelectableBuffer(20); 
      mRenderer.setPanEnabled(true); 

      time_series = new TimeSeries("test"); 
      mDataset.addSeries(time_series); 

      fillData(x); 

      mChartView = ChartFactory.getTimeChartView(this, mDataset, mRenderer, 
       DataBaseHelper.DATE_FORMAT); 



     layout.removeAllViews(); 
     layout.addView(mChartView); 

    } 
}

這是一張垃圾是按鈕的底部後面。任何幫助，將不勝感激。