title: achartengine: duplicated chart after resume
body: <p>I am facing with a werid problem. The demos run well, but in my own app, If I switched to another app, and then switched back, there would be an small duplicated chart on the left bottom.</p>
  
  <p>The chart in my app will be updated(add new (x,y) and repaint) at intervals.</p>
  
  <p>Attached are the original image and image after switched back.</p>
  
  <p>I suspect there are some problems with my onResume() method.</p>
  
  <pre><code>@Override
  protected void onResume() {
      super.onResume();
  
      if (mChartView == null) {
          LinearLayout layout = (LinearLayout) findViewById(R.id.linearlayout_chart);
          mChartView = ChartFactory.getLineChartView(this, mDataSet, mRenderer);
          mRenderer.setClickEnabled(true);
          mRenderer.setSelectableBuffer(100);
  
  
          mChartView.setOnClickListener(new OnClickListener() {
              public void onClick(View v) {
  
              }
          });
          mChartView.setOnLongClickListener(new OnLongClickListener() {
               public boolean onLongClick(View v) {
                   return false;
               }
           });
           mChartView.addZoomListener(new ZoomListener() {
  
               public void zoomApplied(ZoomEvent e) {
               }
               public void zoomReset() {
               }
           }, true, true);
  
           mChartView.addPanListener(new PanListener() {
               public void panApplied() {}
           });
  
           layout.addView(mChartView, new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
      }
  
      mChartView.repaint();
  
  }
  </code></pre>
  
  <p>I cannot figure out why did this happen, does anyone have the same problem?</p>
  
  <p>The normal chart:
  <img src="https://i.stack.imgur.com/pq0Hs.png" alt="normal chart"></p>
  
  <p>After switched back from another app:
  <img src="https://i.stack.imgur.com/dKTgr.png" alt="enter image description here"></p>
  
  <p>Android 3.2 (API Level 13)
  AChartEngine version 0.7.0
  Asus EEE pad</p>