Achart Engine Onclick Not Working Sometimes Error?

I am working on a pie chart and I am using AchartEngine.

I have a pie chart:

Pie chart image

I added onclick to slices, but sometimes only the green onlick fragment won't work.

this is my code:

mChartView = ChartFactory.getPieChartView(this, adc.buildCategoryDataset("Project budget", values), renderer);
        mChartView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              SeriesSelection seriesSelection = mChartView.getCurrentSeriesAndPoint();
              if (seriesSelection == null) {
                  Toast
                      .makeText(GeneratedChartDemo.this, "No chart element was clicked", Toast.LENGTH_SHORT)
                      .show();
                } else {
                  Toast.makeText(
                          GeneratedChartDemo.this,
                      "Chart element data point index " + seriesSelection.getPointIndex()
                          + " was clicked" + " point value=" + seriesSelection.getValue(),
                      Toast.LENGTH_SHORT).show();
                }
            }
          });

      

        
        
        
      

    

Where am I going wrong, am I missing something?

EDIT

Thanks to Dan who helped me solve the problem.