Achartengine绘制额外的垃圾字符

我喜欢用于Android的achartengine图表库，但我一直在收到这个问题。我希望该活动能够通过单击按钮重新绘制来自我的数据库的不同数据集的图表（返回不同的时间量）。在活动中有三个按钮以及图表（在包含图表的列表视图下方）。除了一些额外的垃圾字符被按下后，它们会在按钮后面绘制。它不会在第一次按下按钮时发生，而是在按下按钮时（无所谓）垃圾出现。Achartengine绘制额外的垃圾字符

我的布局：

<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>

我的活动：

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); 

    } 
}

这是一张垃圾是按钮的底部后面。任何帮助，将不胜感激。