Question

嗨，这是我的代码，但不起作用（library的最新版本）

LineData dataChart = mainChart.getData();

    if (dataChart != null) {

        LineDataSet set = (LineDataSet) dataChart.getDataSetByIndex(0);
        if (set == null) {
            set = (LineDataSet) createSet(ColorTemplate.rgb(colorChart), ColorTemplate.rgb(colorFill));
            dataChart.addDataSet(set);
        }



        dataChart.addEntry(new Entry(set.getEntryCount(), sensorEvent.values[2]), 0);
        dataChart.notifyDataChanged();

        if(set.getEntryCount() == 20) {
            set.removeFirst();
        }

        // let the chart know it's data has changed
        mainChart.notifyDataSetChanged();
        // limit the number of visible entries
        mainChart.setVisibleXRangeMaximum(20);
        mainChart.moveViewToX(dataChart.getEntryCount());

    }

`这个鳕鱼的输出： not correct

但是当我改变我的代码时：

LineData dataChart = mainChart.getData();

    if (dataChart != null) {

        LineDataSet set = (LineDataSet) dataChart.getDataSetByIndex(0);
        if (set == null) {
            set = (LineDataSet) createSet(ColorTemplate.rgb(colorChart), ColorTemplate.rgb(colorFill));
            dataChart.addDataSet(set);
        }



        dataChart.addEntry(new Entry(set.getEntryCount(), sensorEvent.values[2]), 0);
        dataChart.notifyDataChanged();

        // let the chart know it's data has changed
        mainChart.notifyDataSetChanged();
        // limit the number of visible entries
        mainChart.setVisibleXRangeMaximum(300);
        mainChart.moveViewToX(dataChart.getEntryCount());

    }

并且输出正确，那么我该怎么做才能从图表中删除旧数据？ correct but I want delet old data

Answer 1

问题解决了。我应该添加这一行。

if(set.getEntryCount() == MAX_ENTRIES) {
            set.removeFirst();
            // change Indexes - move to beginning by 1
            for (Entry entry : set.getValues() )
                entry.setX(entry.getX() - 1);
}

Answer 2

我在先前的答案中发现了一些问题。因此，我尝试了不同的方法。

优点： 1.数据集的条目数保持不变。 2.像ECG这样的实时图形

private long removalCounter = 0;
private static final int VISIBLE_COUNT = 300;

private void addNewEntry(double value) {

    LineData data = lineChart.getData();

    if (data != null) {

        ILineDataSet set = data.getDataSetByIndex(0);

        if (set == null) {
            set = createDataSet();
            data.addDataSet(set);
        }

        data.addEntry(new Entry(set.getEntryCount() + removalCounter, (float) value), 0);
        data.notifyDataChanged();

        // limit the number of visible entries
        lineChart.setVisibleXRangeMaximum(VISIBLE_COUNT);

        // move to the latest entry
        lineChart.moveViewToX(set.getEntryCount());

        //remove entry which is out of visible range 
        if (set.getEntryCount() > VISIBLE_COUNT){
            data.removeEntry(removalCounter, 0);
            removalCounter++;
        }
        lineChart.notifyDataSetChanged();
    }
}


private LineDataSet createDataSet() {

    LineDataSet set = new LineDataSet(null, "real_time");
    set.setAxisDependency(YAxis.AxisDependency.LEFT);
    set.setColor(Color.RED);
    set.setLineWidth(1f);
    set.setDrawCircles(false);
    set.setHighlightEnabled(false);
    set.setDrawValues(false);
    set.setMode(LineDataSet.Mode.HORIZONTAL_BEZIER);
    set.setCubicIntensity(0.2f);
    return set;
}

Answer 3

我也遇到过这个问题。我想在LineChart中显示最后5个条目，所以当数据出现时，我调用addXValue（）和addEntry（）。由于条目数为5，我调用removeXValue（0 ）和removeEntry（0）删除最旧的条目，但LineChart很奇怪：实际上条目数是5，但它最后只有一个条目，现在我不知道怎么处理它。这是我的代码：

private static final int VISIBLE_NUM = 5;

private void refreshData(float value) {
    LineData data = mChart.getData();
    if (data != null) {
        LineDataSet set = data.getDataSetByIndex(0);

        if (set == null) {

            set = new LineDataSet(null, "DataSet");
            set.enableDashedLine(10f, 5f, 0f);
            set.setColor(Color.BLUE);
            set.setCircleColor(Color.GREEN);
            set.setLineWidth(1f);
            set.setCircleSize(3f);
            set.setDrawCircleHole(false);
            set.setValueTextSize(9f);
            set.setFillAlpha(65);
            set.setFillColor(Color.BLACK);

            data.addDataSet(set);
        }

        if(set.getEntryCount() == VISIBLE_NUM) {
            data.removeXValue(0);
            set.removeEntry(0);
        }

        data.addXValue(new SimpleDateFormat("HH:mm:ss")
                .format(new Date(System.currentTimeMillis())));
        data.addEntry(new Entry(value, set.getEntryCount()), 0);

        mChart.notifyDataSetChanged();
        //mChart.setVisibleXRange(VISIBLE_NUM-1);
        //mChart.moveViewToX(data.getXValCount() - VISIBLE_NUM);
        mChart.invalidate();
    }

}

Answer 4

来自this的Adam Wu答案的MPAndroidChart v3.0.2解决方案：

if (set.getEntryCount() >= MAX_ENTRIES) {  
    set.removeFirst();    
    for (int i=0; i<set.getEntryCount(); i++) {  
        Entry entryToChange = set.getEntryForIndex(i);  
        entryToChange.setX(entryToChange.getX() - 1);  
    }  
}

如何在MPAndroidChart中删除旧数据？

4 个答案: