How to move the graph viewport when adding time-based items to a series at runtime? - android-graphview

Question

I'm trying to create a graph with displays the last n seconds of data arriving by bluetooth. I want to add to the series from within a timer by adding a DataPoint with a Date as X value. All I get is a white screen. I think that the problem lies with the values used in ´graph.getViewport().setMinX`.
What value should I set for minX and maxX if I want to display the last n seconds of data?
public class MainActivity extends ActionBarActivity {
private Handler mHandler;
private GraphView graph;
LineGraphSeries<DataPoint> serFl = new LineGraphSeries<DataPoint>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initGraph();
mHandler = new Handler();
startRepeatingTask();
}
private void initGraph() {
try {
graph = (GraphView) findViewById(R.id.graph);
serFl.setColor(Color.BLUE);
graph.addSeries(serFl);
graph.getViewport().setXAxisBoundsManual(true);
graph.getViewport().setMinX(System.currentTimeMillis() - 10000);
graph.getViewport().setMaxX(System.currentTimeMillis() + 1000);
graph.getViewport().setYAxisBoundsManual(true);
graph.getViewport().setMinY(0);
graph.getViewport().setMaxY(20);
final SimpleDateFormat sdf = new SimpleDateFormat("mm:ss");
graph.getGridLabelRenderer().setLabelFormatter(
new DefaultLabelFormatter() {
#Override
public String formatLabel(double value, boolean isValueX) {
if (isValueX) {
Date d = new Date((long) value);
return sdf.format(d);
} else {
// show currency for y values
return super.formatLabel(value, isValueX);
}
}
});
} catch (Exception x) {
System.err.println(x);
}
}
Runnable mStatusChecker = new Runnable() {
#Override
public void run() {
updateStatus();
mHandler.postDelayed(mStatusChecker, mInterval);
}
};
void startRepeatingTask() {
mStatusChecker.run();
}
protected void updateStatus() {
DataMessage msg = source.fetch();
long d = msg.getTimestamp();
serFl.appendData(new DataPoint(d, msg.getFl()), true,
settings.getMaxSeriesSize());
}
void stopRepeatingTask() {
mHandler.removeCallbacks(mStatusChecker);
}
}

Answer 1

You did not
graph.onDataChanged(false, false);
after setting the graph.getViewport().setMaxY(20);.
This helped in my case.