如何在LineChart MPAndroidChart中使用自定义数据？

Question

How can I put a Date in the axis x in LineChart with MPAndroidChart ? Now I'm convert the Date (in milliseconds) to string, but when i try to put is in the chart the x values don't display.

        LineDataSet dataSet = new LineDataSet(entries, getString(R.string.NDVI_trend));
    LineData lineData = new LineData(dataSet);

    chart.setData(lineData);
    Description description = new Description();
    description.setText("");
    chart.setDescription(description);
    chart.getAxisRight().setEnabled(false);
    chart.getXAxis().setPosition(XAxis.XAxisPosition.BOTTOM);
    chart.getXAxis().setDrawGridLines(false);
    chart.getLegend().setEnabled(false);

    String[] dateString = new String[entries.size() +1];
    for (int i = 0; i < entries.size(); i++){
        dateString[i] = getDate((long)entries.get(i).getX(),"dd MMM yyyy");
    }

    IAxisValueFormatter axisValueFormatter = new IndexAxisValueFormatter(dateString);
    chart.getXAxis().setValueFormatter(axisValueFormatter);
    chart.invalidate();

The getData method:

public static String getDate(long milliSeconds, String dateFormat)
{
    SimpleDateFormat formatter = new SimpleDateFormat(dateFormat);

    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(milliSeconds);
    return formatter.format(calendar.getTime());
}

Answer 1

If you know how to convert your float x-values into a String representation of a Date you can use a IAxisValueFormatter :

mChart.getXAxis().setValueFormatter(new IAxisValueFormatter() {
        private SimpleDateFormat mFormat = new SimpleDateFormat("dd MMM HH:mm");

        @Override
        public String getFormattedValue(float value, AxisBase axis) {

            long millis = (long) value;
            return mFormat.format(new Date(millis));
        }
    });
chart.getXAxis().setValueFormatter(axisValueFormatter);
chart.setGranularity(1.0f);
chart.setGranularityEnabled(true);