mpAndroidChart: Bar Chart only accepts fixed height - bar-chart

Question

i am having the same problem as this guy - my bar chart will only accept a fixed height in dp. If I use Fill-Parent, match_parent or wrap_content, the chart will be flat with a height of zero. And working with fixed sizes will not work on different screen sizes.
While this question is already floating around the internet (f.i. here), no one seems to have a decent solution. Any ideas?
android:fillViewport="true" did not help either.
My XML:
<?xml version="1.0" encoding="utf-8"?>
<layout>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingTop="16dp"
tools:context="com.example.myself.myroom.Frontend.StatisticFragment">
<com.github.mikephil.charting.charts.BarChart
android:id="#+id/testchart"
android:layout_width="fill_parent"
android:layout_height="fill_parent"(or fixed number of dp) />
</FrameLayout> </layout>
the according fragment(only the chart part):
protected void onPostExecute(List<ItemS> result) {
// update the UI after background processes completes
List<ItemS> dataObjects = result;
List<BarEntry> entries = new ArrayList<BarEntry>();
final List<String> labels = new ArrayList<String>();
Integer testdummy = 0;
for (ItemS data : dataObjects) {
// turn your data into Entry objects
entries.add(new BarEntry( testdummy, data.get_dAmount().floatValue() ));
labels.add(data.getiCatID().toString());
testdummy++;
}
BarData data = new BarData(new BarDataSet(entries, "Labelerik"));
IAxisValueFormatter formatter = new IAxisValueFormatter() {
#Override
public String getFormattedValue(float value, AxisBase axis) {
return labels.get((int) value);
}
// we don't draw numbers, so no decimal digits needed
//#Override
//public int getDecimalDigits() { return 0; }
};
data.setBarWidth(0.9f); // set custom bar width
oBinding.testchart.setData(data);
oBinding.testchart.setFitBars(true); // make the x-axis fit exactly all bars
oBinding.testchart.getXAxis().setPosition(XAxis.XAxisPosition.BOTTOM);
oBinding.testchart.getXAxis().setGranularity(1f); // minimum axis-step (interval) is 1
oBinding.testchart.getXAxis().setValueFormatter(formatter);
oBinding.testchart.invalidate(); // refresh
}
Thanks for reading!