我正在使用AChartEngine构建一个Android应用,并且遇到了一些奇怪的错误。

在将新点添加到已经建立的图表并触摸/平移图表后,在NullPointerException中得到一个LineChart(XYChart).getSeriesAndPointForScreenCoordinate(Point),其中GraphicalView的变量oldXoldY被发现为空。这些变量在GraphicalView.onTouchEvent()中设置,但是显然没有被调用。

初始化图形时,是否可以手动触发onTouchEvent(),还是可以解决此错误?

这是我的图表设置代码:

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();
        }
    }
});


这是我添加新点的方法:

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;
    }
}


我的测试代码:

for(double i = 0; i < 10; i++) {
    new NewPoints().execute(i, Math.log(i));
}


这是LogCat的输出:

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)


更新1:

我重新编译了AChartEngine源代码,调试显示此方法中发生了错误:

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);
  }


rectangle = area.getRect();行中抛出异常,其中area为null,因为clickableAreas.get(0)以某种方式返回null clickableAreas的集合。

我将尝试通过检查是否clickableArea为null来对此进行修补,但这引出了一个问题:我是否正确添加了点?

最佳答案

根据堆栈跟踪,异常发生在XYChart.java的以下代码的第二行(如果我的源代码具有匹配的行号):

for (ClickableArea area : clickableAreas.get(seriesIndex)) {
    rectangle = area.getRect();  // <--- Exception here!
    if (rectangle != null && rectangle.contains(screenPoint.getX(), screenPoint.getY())) {
        return new SeriesSelection(seriesIndex, pointIndex, area.getX(), area.getY());
    }
    pointIndex++;
}


我不知道怎么回事。

您可以使用AChartEngine的源代码进行编译和调试吗?

进一步的oldXoldY都在GraphicalView.java中声明为原始float。如果它们是原语,怎么能成为null

07-24 09:46
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