android - MPAndroidChart x-axis date/time label formatting

Question

Background

For some charts in my app, I'm using the MPAndroidChart library. All horizontal axis' of my graphs are time based, they can span a full year, a month, a week, a day or span one hour. It always shows a full period, so January-December, Monday-Sunday, 0:00 - 24:00 etc. The value of the axis is always the epoch-timestamp (in seconds).

Requirement

I want the x-axis labels to follow these rules:

• at 1st of month in case of year span;
• at start of day in case of month or week span;
• on any full hour (##:00) (not perse all) in case of a day span;
• on any 5 minute point on an hour span.

Problem

I can set the granularity of the x-axis, which makes sure there is no less space between two points then the granularity says, but that can mean that (in case of day span) the first label is at 1:00am, and the second at 2:01am and the third is at 3:16am, since that fits a granularity of (minimum) 60 minutes.

Current incorrect situation, which would ideally be something like [0:00, 3:00, 6:00, 9:00 ..]

Question

Is there a way to control the positioning of the x-axis labels to achieve the results above?

Answer 1

I have done same thing, Try this,

 XAxis xAxis = mChart.getXAxis();
    xAxis.setPosition(XAxis.XAxisPosition.BOTTOM_INSIDE);
    xAxis.setDrawGridLines(false);
    xAxis.setGranularity(1f); // only intervals of 1 day
    xAxis.setTypeface(mTfLight);
    xAxis.setTextSize(8);
    xAxis.setTextColor(ContextCompat.getColor(this, R.color.colorYellow));
    xAxis.setValueFormatter(new GraphXAxisValueFormatter(range, interval, slot));

in this range in your case. If you want month then there is 12, in case of week 7 etc.

in interval you pass 1.

in slot you have to pass, identification of your data like month, year, day, i have use enum for this.

public class GraphXAxisValueFormatter implements IAxisValueFormatter {

private static int MINUTES_INTERVAL = 5;
private String[] mValues;
private int mInterval;
private SensorInterval.Interval mSlot;

public GraphXAxisValueFormatter(List<BinSensorData> range, int interval, SensorInterval.Interval slot) {
    mValues = new String[range.size()];
    mInterval = interval;
    mSlot = slot;

    Calendar calendar = Calendar.getInstance();
    for (int i = 0; i < range.size(); i++) {
        calendar.setTimeInMillis(range.get(i).getTime());

        int unroundedMinutes = calendar.get(Calendar.MINUTE);
        int mod = unroundedMinutes % MINUTES_INTERVAL;
        calendar.add(Calendar.MINUTE, mod < 8 ? -mod : (MINUTES_INTERVAL - mod));


        String s = "";

        if (slot.equals(SensorInterval.Interval.HOUR) || slot.equals(SensorInterval.Interval.DAY))
            s = Util.getTimeFromTimestamp(calendar.getTimeInMillis());
        else if (slot.equals(SensorInterval.Interval.WEEK))
            s = Util.getDayFromTimestamp(calendar.getTimeInMillis());
        else if (slot.equals(SensorInterval.Interval.MONTH))
            s = Util.getMonthFromTimestamp(calendar.getTimeInMillis());
        else if (slot.equals(SensorInterval.Interval.YEAR))
            s = Util.getYearFromTimestamp(calendar.getTimeInMillis());


        Util.setLog("Time : "+s);
        mValues[i] = s;
    }
}

@Override
public String getFormattedValue(float value, AxisBase axis) {
    Util.setLog("Value : "+ value);
    if (value % mInterval == 0 && value >= 0) {
        return mValues[(int) value % mValues.length];
    } else
        return "";

}

@Override
public int getDecimalDigits() {
    return 0;
}

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