合并的图表BarData.getDataSetCount（）清除图表以某种方式？

Question

我有以两种不同方式构建的组合图（折线图或蜡烛+折线+条形图）。 第一次加载时，两种方法都可以正常工作（使用第一种或第二种方法来初始化应用程序-可以）。

如果我绘制第二组图表，然后尝试绘制第一条折线图-我正在获得NPE： java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'int com.github.mikephil.charting.data.BarData.getDataSetCount（）'

在该行代码上：mCombinedChart.setData（combinedData）;

我认为我需要以某种方式清除图表或它是错误？

我的代码：

private void buildChart(ArrayList graphData, final CoinExchangeData coin) {
mCombinedChart.clear();

//axis

YAxis yAxisRight = mCombinedChart.getAxisRight();
yAxisRight.setSpaceBottom(220f);
yAxisRight.setEnabled(true);
yAxisRight.setTextColor(getResources().getColor(R.color.landscape_chart_text_active));

YAxis yAxisLeft = mCombinedChart.getAxisLeft();
yAxisLeft.setEnabled(false);

XAxis xAxis = mCombinedChart.getXAxis();
xAxis.setEnabled(false);
xAxis.setTextColor(getResources().getColor(R.color.landscape_chart_text_active));
xAxis.setValueFormatter(new XAxisValueFormatter(graphData));

mCombinedChart.setTouchEnabled(true);
mCombinedChart.setHighlightPerDragEnabled(true);
mCombinedChart.setHighlightPerTapEnabled(true);


mCombinedChart.getDescription().setEnabled(false);

mCombinedChart.setScaleEnabled(false);
mCombinedChart.setDoubleTapToZoomEnabled(false);

mCombinedChart.setNoDataText(App.getContext().getResources().getString(R.string.graph_no_data));

//Line chart
if (App.getPreferencesInstance().getInt(PreferencesManager.LANDSCAPE_CHART_MODE_KEY, PreferencesManager.LANDSCAPE_CHART_MODE_LINE) == PreferencesManager.LANDSCAPE_CHART_MODE_LINE) {
    mCombinedChart.getLegend().setEnabled(false);

    Legend legend = mCombinedChart.getLegend();
    legend.setEnabled(true);
    legend.setTextColor(getResources().getColor(R.color.landscape_chart_legend));
    legend.setVerticalAlignment(Legend.LegendVerticalAlignment.TOP);

    List<Entry> values = new ArrayList<>();

    for (int i = GRAPH_OFFSET; i < graphData.size(); ++i) {
        values.add(new Entry((float) i, graphData.get(i).high.floatValue()));
    }

    LineDataSet lineDataSet = new LineDataSet(values, coin.symbol);
    lineDataSet.setDrawValues(false);
    lineDataSet.setDrawCircles(false);
    lineDataSet.setAxisDependency(YAxis.AxisDependency.RIGHT);

    chartMin =  lineDataSet.getYMin();
    chartMax = lineDataSet.getYMax();
    mCombinedChart.getAxisRight().setAxisMinimum(chartMin);
    mCombinedChart.getAxisRight().setAxisMaximum(chartMax);


    lineDataSet.setDrawFilled(true);
    lineDataSet.setFillDrawable(LandscapeChartActivity.this.getResources().getDrawable(R.drawable.gradient_landscape_chart));


    lineDataSet.setColor(LandscapeChartActivity.this.getResources().getColor(R.color.landscape_chart_gold));
    lineDataSet.setLineWidth(2.0f);

    LineData lineData = new LineData(lineDataSet);

    if (lineData.getEntryCount() == 0) {
        showChartReload();
        return;
    }

    CombinedData combinedData = new CombinedData();
    combinedData.setData(lineData);

    mCombinedChart.setData(combinedData);
} else {  // Candle chart
    List<CandleEntry> valuesRateData = new ArrayList<>();
    List<BarEntry> valuesVolumeData = new ArrayList<>();

    for (int i = GRAPH_OFFSET; i < graphData.size(); ++i) {
        GraphPoint graphPoint = graphData.get(i);

        valuesRateData.add(new CandleEntry((float) i - GRAPH_OFFSET, graphPoint.high.floatValue(), graphPoint.low.floatValue(),
                graphPoint.open.floatValue(), graphPoint.close.floatValue()));
        valuesVolumeData.add(new BarEntry((float) i - GRAPH_OFFSET, graphPoint.volume.floatValue()));
    }

    CandleDataSet candleDataSet = new CandleDataSet(valuesRateData, coin.fullName.concat(" (").concat(coin.symbol).concat(")"));
    candleDataSet.setDrawValues(false);

    BarDataSet barDataSet = new BarDataSet(valuesVolumeData, getResources().getString(R.string.volume));
    barDataSet.setAxisDependency(YAxis.AxisDependency.LEFT);
    barDataSet.setColor(getResources().getColor(R.color.landscape_chart_volumes_bars));

    //chart.getXAxis().setTextColor(getResources().getColor(R.color.graph_axis));
    //chart.getAxisRight().setTextColor(getResources().getColor(R.color.graph_axis));


    yAxisLeft.setSpaceTop(400f);
    yAxisLeft.setEnabled(false);

    yAxisRight.setSpaceBottom(20f);

    candleDataSet.setAxisDependency(YAxis.AxisDependency.RIGHT);
    //candleDataSet.setDrawFilled(true);
    candleDataSet.setIncreasingColor(getResources().getColor(R.color.landscape_chart_green));
    candleDataSet.setDecreasingColor(getResources().getColor(R.color.landscape_chart_red));
    candleDataSet.setNeutralColor(getResources().getColor(R.color.landscape_chart_candle_shadow));
    candleDataSet.setShadowColor(getResources().getColor(R.color.landscape_chart_candle_shadow));
    candleDataSet.setIncreasingPaintStyle(Paint.Style.FILL);
    candleDataSet.setShadowWidth(0.66f);
    candleDataSet.setHighLightColor(getResources().getColor(R.color.landscape_chart_gold));

    CandleData candleData = new CandleData(candleDataSet);

    CombinedData combinedData = new CombinedData();
    combinedData.setData(candleData);

    BarData barData = new BarData(barDataSet);
    combinedData.setData(barData);

    if (App.getPreferencesInstance().getInt(PreferencesManager.LANDSCAPE_INDICATOR_KEY, PreferencesManager.LANDSCAPE_INDICATOR_WMA7) == PreferencesManager.LANDSCAPE_INDICATOR_WMA7) {
        ArrayList<PointXY> points = Indicators.evaluateIndicatorWMA7(graphData);

        List<Entry> valuesWMA7Data = new ArrayList<>();

        for (int i = 0; i < points.size(); ++i) {
            valuesWMA7Data.add(new Entry(points.get(i).x.floatValue(), points.get(i).y.floatValue()));
        }

        LineDataSet indicatorWMA7DataSet = new LineDataSet(valuesWMA7Data, "WMA7");
        indicatorWMA7DataSet.setAxisDependency(YAxis.AxisDependency.RIGHT);
        indicatorWMA7DataSet.setColor(getResources().getColor(R.color.landscape_chart_indicator));
        indicatorWMA7DataSet.setDrawCircles(false);
        indicatorWMA7DataSet.setLineWidth(1.2f);

        LineData lineDataWMA7 = new LineData(indicatorWMA7DataSet);

        combinedData.setData(lineDataWMA7);
    }

    mCombinedChart.setData(combinedData);
}
    showChart(coin);
}