Develop Reference

Passing current time in milliseconds to MPChart breaks it

I have tried figuring this out, but it doesn't add up. The data doesn't appear as it should.
First I generate dummy data. This is done async because I need time between the calls to System.currentTimeMillis to get some spacing between them. (Look aside the crappy code here, this is just debug data that will not be in the release. Using Thread.sleep on the main thread is a bad idea considering ANR's)
public class AsyncGeneration extends AsyncTask<String, String, String>{
public AsyncGeneration() {
super();
}
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
}
#Override
protected void onCancelled(String s) {
super.onCancelled(s);
}
#Override
protected void onCancelled() {
super.onCancelled();
}
#Override
protected String doInBackground(String... strings) {
while(root == null) {
try {
Thread.sleep(200);
}catch(InterruptedException e){}
}
List<Entry> rdata = new ArrayList<>();
for(int i = 1; i < 30; i++){
try{
Thread.sleep(200);
}catch(Exception e){
//IGNORE
}
float time = System.currentTimeMillis();
Log.e("GChart", "Timex: " + time);
Session s = new Session(r.nextInt(5000), time);//Replace time with the index in the for-loop and it works for some reason
rdata.add(new Entry(s.getXValue(), s.getYValue()));
Log.e("GChart", "Timey: " + s.getXValue());
}
final List<Entry> entries = rdata;
OverviewFragment.this.getActivity().runOnUiThread(() ->{
LineDataSet data = new LineDataSet(entries, "Distance");
data.setCircleColor(Color.parseColor("#FF0000"));
LineData lineData = new LineData(data);
tab1chart.setData(lineData);
tab1chart.invalidate(); // refresh
tab1chart.getXAxis().setValueFormatter(new DateFormatter());
tab1chart.getXAxis().setPosition(XAxis.XAxisPosition.BOTTOM);
tab1chart.getXAxis().setTextSize(10f);
tab1chart.getXAxis().setTextColor(Color.RED);
tab1chart.getXAxis().setDrawAxisLine(true);
tab1chart.getXAxis().setDrawGridLines(true);
tab1chart.getAxisLeft().setValueFormatter(new DistanceValueFormatter());
tab1chart.getAxisLeft().setDrawGridLines(true);
Log.v("Chart", "Chart data loaded and invalidated");//This prints
});
return null;
}
}
So far everything looks fine. The data gets put into the chart, no exceptions, no crashes.
When the chart renders, a single data point shows up at the far-left of the chart. I generate 30 data points, one shows up.
That's issue #1: Only one data point shows up.
Issue #2 is slightly harder. The entire X axis at the bottom disappears. X axis is gone and when zooming, the Y axis, and its text also disappears. This is fairly hard to explain, so here is a screenshot:
It is worth mentioning the fact that if I pass i in the for-loop as the time, it shows up just as expected: all the axises are in place, zoom doesn't break anything.
(Float values can take the same values as Longs except they have decimals in addition.)
And in addition, I format the data:
public class DateFormatter implements IAxisValueFormatter {
SimpleDateFormat formatter;
public DateFormatter(){
formatter = new SimpleDateFormat("dd/MM/yy, HH:mm");
}
#Override
public String getFormattedValue(float value, AxisBase axis) {
//This method is never called. Nothing is returned
if(axis instanceof XAxis) {
String formatted = formatter.format(new Date((long) value));
Log.d("Formatter", "Formatted \"" + value + "\" to \"" + formatted + "\".");
return formatted;
}
return "Not supported";
}
}
Removing the formatter doesn't change anything, the axis is still gone. Zoom still breaks the Y axis.
So my question is: How do I fix this? I don't get why the chart doesn't work when I pass the current time in milliseconds (and I checked the values with debug output, floats can handle it). I got some debug output earlier that eventually stopped coming at all that showed the value passed to the formatter was values < 2000. I can't reproduce this any more though
The chart itself doesn't appear to be broken but from touch events it looks like every single point is pushed into the same X coordinate but only one point renders. When I touch the chart, the orange-ish lines show up indicating the position of a data point. It pops up on points that aren't visible.
When I pass the for-loop index as the X value, it works as expected, the formatter works fine (looking aside the fact that it shows the date as in 1970, but it is counted as 1 millisecond into the epoch, so that is to expect)
I looked at this as well on formatting the date. When I then try passing the milliseconds since the epoch, the chart stops working.
I'm using MPChart v 3.0.2, compiling against Android 26, using Java 8, and running Android Studio 3.0 beta 2
As for the layout, it is just a LinearLayout with a LineChart in it.
This should work, but it breaks when I pass it the current time in milliseconds for some reason. Passing any other data (as long as the numbers aren't that big) works fine.
The two images are not how the chart is supposed to look. The X axis is supposed to be visible, but for some reason it isn't along with a large amount of the data.

This is known issue of Android MPChart (have a read this thread). Time series chart supported in MPChart - You can set time (in millis) as X values for Hourly Charts.
But too many consecutive data (points) won't correctly plot in Line Charts. Because Entry object will accept only float values due to some performance constraints.
So, keep the first value as the reference and subtract each up coming value from reference value & divide by some constants (say 1000) .So , you X value set will be like 10,20,30....& so on.
Do the reverse logic in your Axis Value formatter to render the X Axis Label properly (see the code snippet).
lineChart.getXAxis().setValueFormatter(new IAxisValueFormatter() {
#Override
public String getFormattedValue(float value, AxisBase axis) {
SimpleDateFormat format2 = new SimpleDateFormat("HH:mm:ss");
return format2.format(new Date(firstTimeStamp + ((long) value) * 1000L));
}
});

How to handle time series in MPAndroidChart?

I want to add the following sort of data (can be any number of such pairs under 1000) to the newly introduced timeseries chart in MPAndroidChart library
Value : 50.0 at 1472112259
Value : 49.0 at 1472112294
Value : 50.0 at 1472112329
Value : 50.0 at 1472112360
Value : 50.0 at 1472112392
The following data will be fetched from the array.
Right now, I guess there is some mess up with the timestamps.
Here is the complete code: https://gist.github.com/utkarshns/e1723dcc57022fcd392bc3b127b6c898
UNIX timestamps will be parsed to required time format after I can successfully add values to the graph.
Currently, the problem I face is that the timestamps probably get clipped and values are overwritten which leads to a pretty messed up graph with really weird x-axis values.
Update:
Screenshots:
http://imgur.com/a/dGfmz

The problem is that Float values can't hold very big numbers and still be accurate, so you need a separate List with these timestamp values. BigDecimal should be ok for this purpose. Your distances must be in accordance to the time gaps between your events. Just iterate from the start date to end date keeping count of how many timestamps you have and add Entry with count from the timestamps you wish your value to be.
Long myValues[] = {1472112259L, 1472112294L, 1472112329L, 1472112360L, 1472112392L};// your values
ArrayList<Entry> values = new ArrayList<>();// Entry List
Long start = 1472112259L;//start
Long end = 1472112392L;//end
List<BigDecimal> mList = new ArrayList<>(); //Decimal list which holds timestamps
int count = 0;
for (Long i = start; i <= end; i++) {
mList.add(new BigDecimal(i));
if (myValues.equals(i)) {
values.add(new Entry(count, 50));
}
count++;//always increment
}
And your ValueFormatter should look like this:
AxisValueFormatter() {
private FormattedStringCache.Generic<Long, Date> mFormattedStringCache = new FormattedStringCache.Generic<>(new SimpleDateFormat("HH:mm:ss"));
#Override
public String getFormattedValue ( float value, AxisBase axis){
return mFormattedStringCache.getFormattedValue(new Date(mList.get((int)value).longValueExact()*1000), value);
}
#Override
public int getDecimalDigits () {
return 0;
}
}
If you have any question or something is unclear I'll be happy to help.

Customsing x-axis labels in android-graphview

I am using android-graphview to display bar graph in android app. On X-axis I want to display labels as 'day-of-the-week,hour-of-the-day' like 'Mon,14.00'. So original x value(it may be date or time in milliseconds) in data point is totally done away with. I know we can do some customization in setLabelFormatter, but as far as I understand you can do some append to original value, not totally remove it.
Is there a way out for it?

use the DefaultLabelFormatter override the format method and call the super implementation. then you can append your text to the string.
Example:
graph.getGridLabelRenderer().setLabelFormatter(new DefaultLabelFormatter() {
#Override
public String formatLabel(double value, boolean isValueX) {
if (isValueX) {
// show normal x values
return super.formatLabel(value, isValueX);
} else {
// show currency for y values
return super.formatLabel(value, isValueX) + " €";
}
}
});

MPAndroidChart Linechart unconnected data points

I am investigating MPAndroidChart for usage in my company's Android and iOS application and I have found a problem that I need a solution to in order to be able to use this framework.
The application will mostly use the Line Chart functionality and the supplied data can contain NULL entries. I have seen other posts that discusses this matter and apparently there is no solution to showing NULL values yet. MPAndroidChart with null values
The author suggests simply not adding the data point to the set, but in my case it's very important that there is a "hole" in the graph were there is more than two consecutive NULL values (or however to represent it) i.e that the graph is not continous between two points with NULL values in between. Is there any way I can accomplish this with this framework?
I have been looking into the possibility of separating the data points into different data sets, but it seems like kind of a hack.
Thank you!
Dataset example:
[1 2 10 NULL NULL NULL 20 25 30]
The Line must NOT connect the numbers 10 and 20.

This is what I ended up coming up with to solve this - for anyone in the future. It iterates through and creates new entries in a data set until it hits a null value, and then it creates data sets with "fake" entries that use a boolean in the entry constructor. Boolean can be found from
"entry.getData()"
and you can then you can use this to set that Dataset to not be visible
"mLineDataSet.setVisible(false);"
Note: Do not try to set Dataset Color to transparent - the library has a bug where if certain entries are null the graph doesn't even appear.
private void createDataSets() {
for (int index = 0; index < mGraph.getGraphDataSets().size(); index++) {
lastIndexCreated = 0;
final GraphDataSet mDataSet = mGraph.getGraphDataSets().get(index);
final ArrayList<Entry> mEntries = getEntries(mDataSet.getYValues(), lastIndexCreated);
final LineDataSet mLineDataSet = getDataSet(mEntries, mDataSet, color);
mGraphLineData.addDataSet(mLineDataSet);
lastIndexCreated = mEntries.size() - 1;
while (lastIndexCreated < mDataSet.getYValues().size() - 1) {
final LineDataSet set = getDataSet(mEntriesSet, mDataSet, colorSecondary);
if (mEntriesSet.size() != 0)
mGraphLineData.addDataSet(set);
lastIndexCreated = (int) mEntriesSet.get(mEntriesSet.size() - 1).getX();
}
}
}
private ArrayList<Entry> getEntries(final List<Float> yValues, final int firstValueIndex) {
final ArrayList<Entry> mEntries = new ArrayList<>();
for (int i = firstValueIndex; i < yValues.size(); i++) {
if (yValues.get(i) != null)
//boolean here is false means that dataset is not fake and should be shown
mEntries.add(new Entry(i, yValues.get(i), false));
else if (firstValueIndex == i) {
//add a "Fake" data entry, and use mEntry.getData to set line to not be visible.
mEntries.add(new Entry(i, 0, true));
break;
} else {
break;
}
}
return mEntries;
}

How to make a realtime rollingwindow graph using MPAndroidChart

[also posted on MPAndroidChart's Github]
I need realtime graph with a rolling windows, that's when I ran into 'problems'. Adding data is no problem, but after adding data with an Xvalue(index) that's higher than the current width of the graph the graph doesn't autoscroll because it don't seem to be able to always display [X] Xvalues.
Example of issue:
The result in graph 3 is not what I want for displaying realtime data. A scrollingwindow is much more usefull. So I tried to archieve this..
My working 'solution' was to remove the first Xvalue, add a new one and move all Xindexes of all Entries on screen one to the left. The result is some code like this:
int GRAPH_WIDTH = 10;
LineData lineData = chart.getData();
LineDataSet lineDataSet = lineData.getDataSetByIndex(0);
int count = lineDataSet.getEntryCount();
// Make rolling window
if (lineData.getXValCount() <= count) {
// Remove/Add XVal
lineData.getXVals().add("" + count);
lineData.getXVals().remove(0);
// Move all entries 1 to the left..
for (int i=0; i < count; i++) {
Entry e = lineDataSet.getEntryForXIndex(i);
if (e==null) continue;
e.setXIndex(e.getXIndex() - 1);
}
// Set correct index to add value
count = GRAPH_WIDTH;
}
// Add new value
lineData.addEntry(new Entry([random value], count), 0);
// Make sure to draw
chart.notifyDataSetChanged();
chart.invalidate();
This works quite well actually (as seen in this video here ), but I feel like there must be an easier way to do this. Maybe I overlooked some API window/scrolling..
But if this is the 'right' way to archieve this result then it would be an enhancement to add support for this kind of graphs in your library.

Thank you for the video.
I am surprised you found a workaround that is rather complicated but works quite well.
Unfortunately this is currently the only way to achieve what you want. I will work on making this easier soon probably reusing some of your code.
Also take a look at these two methods:
setScaleMinima(...)
centerViewPort(...)

I took your code and changed it a bit. It will only show up to GRAPH_WIDTH number of points at a time. Then it scrolls along deleting the older data. Useful if you're only interested in relatively recent data. Is that what you were going for?
public void addTimeEntry() {
String entry_date_time = new SimpleDateFormat("MMM d - HH:mm:ss").format(new Date());
LineData lineData = mChart.getData();
int GRAPH_WIDTH = 15;
if (lineData != null) {
LineDataSet set = lineData.getDataSetByIndex(0);
if (set == null) {
set = createSet();
lineData.addDataSet(set);
}
// Make rolling window
if (lineData.getXValCount() > GRAPH_WIDTH) {
lineData.getXVals().remove(0);
set.removeEntry(0);
lineData.getXVals().add(entry_date_time);
lineData.addEntry(new Entry((float) (Math.random() * 40) + 30f, GRAPH_WIDTH), 0);
// lineData.getXVals().add(entry_date_time);
// Move all entries 1 to the left..
for (int i=0; i < set.getEntryCount(); i++) {
Entry e = set.getEntryForXIndex(i);
if (e==null) continue;
e.setXIndex(e.getXIndex() - 1);
}
}
else{
lineData.getXVals().add(entry_date_time);
lineData.addEntry(new Entry((float) (Math.random() * 40) + 30f, lineData.getXValCount()-1), 0);
}
// let the chart know it's data has changed
mChart.notifyDataSetChanged();
mChart.invalidate();
}
}