MPAndroidChart StackedBarChart showing values but no bars

Question

I am starting to use the MPAndroidChart library to build a StackedBarChart showing three y values. Here is the code:

public class Plot
{
    final Context context;
    final BarData data;

    private int count;

    public StackedBarPlot(Context context)
    {
        this.context = context;
        data = setData();
    }

    protected BarData setData()
    {
        final List<BarEntry> entries = new ArrayList<>();
        for (DatabaseEntry entry : entryList)
        {
            final float total = (float) entry.getTotal();
            final float[] y = {100 * entry.getN1() / total,
                    100 * entry.getN2() / total, 100 * entry.getN3() / total};
            entries.add(new BarEntry(/*long*/entry.getDate(), y));
        }
        count = entries.size();


        final BarDataSet dataset = new BarDataSet(entries, null);
        dataset.setColors(new int[]{R.color.green, R.color.blue, R.color.red}, context);
        dataset.setStackLabels(labels);
        dataset.setDrawValues(true);
        dataset.setVisible(true);

        final BarData data = new BarData(dataset);
        data.setBarWidth(0.9f);
        return data;
    }

    public BarChart getChart(int id, View view)
    {
        final BarChart chart = (BarChart) view.findViewById(id);   

        chart.getAxisRight().setEnabled(false);
        chart.getAxisLeft().setEnabled(false);
        final Legend legend = chart.getLegend();
        legend.setDrawInside(true);
        legend.setVerticalAlignment(Legend.LegendVerticalAlignment.TOP);
        legend.setHorizontalAlignment(Legend.LegendHorizontalAlignment.CENTER);

        final XAxis xAxis = chart.getXAxis();
        xAxis.setValueFormatter(dateFormatter);
        xAxis.setPosition(XAxis.XAxisPosition.BOTTOM);
        xAxis.setDrawGridLines(false);
        xAxis.setLabelCount(count);

        chart.getDescription().setEnabled(false);
        chart.setData(data);
        chart.setFitBars(true);
        chart.invalidate();
        return chart;
    }

    private final IAxisValueFormatter dateFormatter = new IAxisValueFormatter()
    {
        @Override
        public String getFormattedValue(float value, AxisBase axis)
        {
            return new DateTime((long) value).toString(context.getString("E, MMM d"));
        }
    };
}

Then in my Fragment, I call:

public class MyFragment extends Fragment
{
    private Plot plot;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        plot = new Plot(getActivity());
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState)
    {
        final View view = inflater.inflate(R.layout.fragment, parent, false);
        plot.getChart(R.id.chart, view);
        return view;
    }
}

And in MainActivity.java

getFragmentManager().beginTransaction().replace(R.id.content, fragment).commit();

main_activity.xml

 <android.support.v4.widget.DrawerLayout
    android:id="@+id/drawer_layout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/AppTheme.PopupOverlay"/>

        </android.support.design.widget.AppBarLayout>

        <FrameLayout
            android:id="@+id/content"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"/>
    </android.support.design.widget.CoordinatorLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/navigation"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/drawer_header"
        app:menu="@menu/navigation"/>

</android.support.v4.widget.DrawerLayout>

fragment.xml

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">

    <com.github.mikephil.charting.charts.BarChart
        android:id="@+id/chart"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</RelativeLayout>

The problem is the bars are not rendering correctly. I can see values but the bars are not displaying in the chart. Any advice?

Answer 1

This is not an error in the library like some of the previous posts have suggested. Probably you are just misunderstanding how the width of each bar is determined like I did at first.

I was using a long, millisecond time-stamp for my x-axis on my bar chart. I realized that by default MPAndroidChart sets the width of a bar to 0.85f. Think about what this means. My first time-stamp was 1473421800000f and the next was 1473508200000f: a difference of 86400000f! Now how could I expect to see a bar that is 0.85f wide when there is 86400000f between each pair of observations?? To fix this problem you need to do something like the following:

barData.setBarWidth(0.6f * widthBetweenObservations);

So the above sets the width of a bar to equal 60% of the distance between observations.