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POAChartEngine crashes after adding points and panning
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copied!<p>I'm building an Android app with <a href="http://code.google.com/p/achartengine" rel="nofollow">AChartEngine</a> and am getting weird errors.</p> <p><strong>After I add new points to my already established chart and touch/pan the graph, I get a <code>NullPointerException</code></strong> in <code>LineChart(XYChart).getSeriesAndPointForScreenCoordinate(Point)</code>, where <code>GraphicalView</code>'s variables <code>oldX</code> and <code>oldY</code> are discovered to be null. These variables are set in <code>GraphicalView.onTouchEvent()</code>, but that is apparently not being called.</p> <p>Is there a way to manually trigger <code>onTouchEvent()</code> when initializing my graph, or is there a workaround to this error?</p> <p>Here is my chart set up code:</p> <pre><code>mChartView = ChartFactory.getLineChartView(this, mDataset, mRenderer); mChartView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { SeriesSelection seriesSelection = mChartView.getCurrentSeriesAndPoint(); double[] xy = mChartView.toRealPoint(0); if (seriesSelection == null) { Toast.makeText(viewer.this, "No chart element was clicked", Toast.LENGTH_SHORT).show(); } else { Toast.makeText( viewer.this, "Chart element clicked", Toast.LENGTH_SHORT) .show(); } } }); </code></pre> <p>Here is how I add new points:</p> <pre><code>protected class NewPoints extends AsyncTask<Double, Void, Void> { @Override protected Void doInBackground(Double... values) { mCurrentSeries.add(values[0], values[1]); // x, y if (mChartView != null) { mChartView.repaint(); } return null; } } </code></pre> <p>My testing code:</p> <pre><code>for(double i = 0; i < 10; i++) { new NewPoints().execute(i, Math.log(i)); } </code></pre> <p>Here is the LogCat output:</p> <pre><code>07-20 18:46:12.570: E/AndroidRuntime(13800): FATAL EXCEPTION: main 07-20 18:46:12.570: E/AndroidRuntime(13800): java.lang.NullPointerException 07-20 18:46:12.570: E/AndroidRuntime(13800): at org.achartengine.chart.XYChart.getSeriesAndPointForScreenCoordinate(XYChart.java:840) 07-20 18:46:12.570: E/AndroidRuntime(13800): at org.achartengine.GraphicalView.getCurrentSeriesAndPoint(GraphicalView.java:135) 07-20 18:46:12.570: E/AndroidRuntime(13800): at com.maximz.viewer$1.onClick(viewer.java:185) 07-20 18:46:12.570: E/AndroidRuntime(13800): at android.view.View.performClick(View.java:3511) 07-20 18:46:12.570: E/AndroidRuntime(13800): at android.view.View$PerformClick.run(View.java:14110) 07-20 18:46:12.570: E/AndroidRuntime(13800): at android.os.Handler.handleCallback(Handler.java:605) 07-20 18:46:12.570: E/AndroidRuntime(13800): at android.os.Handler.dispatchMessage(Handler.java:92) 07-20 18:46:12.570: E/AndroidRuntime(13800): at android.os.Looper.loop(Looper.java:137) 07-20 18:46:12.570: E/AndroidRuntime(13800): at android.app.ActivityThread.main(ActivityThread.java:4424) 07-20 18:46:12.570: E/AndroidRuntime(13800): at java.lang.reflect.Method.invokeNative(Native Method) 07-20 18:46:12.570: E/AndroidRuntime(13800): at java.lang.reflect.Method.invoke(Method.java:511) 07-20 18:46:12.570: E/AndroidRuntime(13800): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 07-20 18:46:12.570: E/AndroidRuntime(13800): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 07-20 18:46:12.570: E/AndroidRuntime(13800): at dalvik.system.NativeStart.main(Native Method) </code></pre> <p><strong>Update 1:</strong></p> <p>I've recompiled with the AChartEngine source code and debugging shows that the error takes place in this method:</p> <pre><code>public SeriesSelection getSeriesAndPointForScreenCoordinate(final Point screenPoint) { if (clickableAreas != null) for (int seriesIndex = clickableAreas.size() - 1; seriesIndex >= 0; seriesIndex--) { // series 0 is drawn first. Then series 1 is drawn on top, and series 2 // on top of that. // we want to know what the user clicked on, so traverse them in the // order they appear on the screen. int pointIndex = 0; if (clickableAreas.get(seriesIndex) != null) { RectF rectangle; for (ClickableArea area : clickableAreas.get(seriesIndex)) { rectangle = area.getRect(); // EXCEPTION HERE: area is null if (rectangle != null && rectangle.contains(screenPoint.getX(), screenPoint.getY())) { return new SeriesSelection(seriesIndex, pointIndex, area.getX(), area.getY()); } pointIndex++; } } } return super.getSeriesAndPointForScreenCoordinate(screenPoint); } </code></pre> <p>The exception is thrown at the <code>rectangle = area.getRect();</code> line, where <code>area</code> is null since <strong><code>clickableAreas.get(0)</code> somehow returns a collection of null clickableAreas</strong>.</p> <p>I'm going to try to patch this with a check to see if the clickableArea is null, but this begs the question: <strong>am I adding points correctly?</strong></p>

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