我想在我的应用程序中使用折线图，我想在设置为线性布局1的背景图像的图像下方显示它，在第二个线性布局中我想添加折线图，我正在使用achart引擎库。第66行的空指针异常（layout.addView（mChartView，new LayoutParams（LayoutParams.FILL_PARENT，LayoutParams.FILL_PARENT））;）请帮忙
package com.android.linegraph;
import java.util.ArrayList;
import java.util.List;
import org.achartengine.ChartFactory;
import org.achartengine.GraphicalView;
import org.achartengine.chart.PointStyle;
import org.achartengine.model.XYMultipleSeriesDataset;
import org.achartengine.model.XYSeries;
import org.achartengine.renderer.XYMultipleSeriesRenderer;
import org.achartengine.renderer.XYSeriesRenderer;
import android.app.Activity;
import android.graphics.Color;
import android.graphics.Paint.Align;
import android.os.Bundle;
import android.util.Log;
import android.view.ViewGroup.LayoutParams;
import android.widget.LinearLayout;
public class LineGraph extends Activity {
private GraphicalView mChartView;
XYMultipleSeriesRenderer renderer;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
LinearLayout layout = (LinearLayout) findViewById(R.id.linearLayout2);
String[] titles = new String[] { "spens1" };
List<double[]> x = new ArrayList<double[]>();
x.add(new double[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 });
// }
List<double[]> values = new ArrayList<double[]>();
values
.add(new double[] { 9, 10, 11, 15, 19, 23, 26, 25, 22, 18, 13,
10 });
int[] colors = new int[] { Color.BLUE };
PointStyle[] styles = new PointStyle[] { PointStyle.CIRCLE };
renderer = buildRenderer(colors, styles);
int length = renderer.getSeriesRendererCount();
for (int i = 0; i < length; i++) {
((XYSeriesRenderer) renderer.getSeriesRendererAt(i))
.setFillPoints(true);
}
setChartSettings(renderer, "SCORE CARD VIEW", "Attetempts",
"Marks Scored", 0.5, 12.5, -10, 40, Color.LTGRAY, Color.LTGRAY);
renderer.setXLabels(12);
renderer.setYLabels(10);
renderer.setShowGrid(true);
renderer.setXLabelsAlign(Align.RIGHT);
renderer.setYLabelsAlign(Align.RIGHT);
renderer.setZoomButtonsVisible(true);
renderer.setPanLimits(new double[] { -10, 20, -10, 40 });
renderer.setZoomLimits(new double[] { -10, 20, -10, 40 });
if (mChartView == null) {
Log.d("Oncreate ", "if (mChartView == null)");
mChartView = ChartFactory.getLineChartView(this, mDataset(titles,
x, values), renderer);
layout.addView(mChartView, new LayoutParams(
LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
} else {
// mChartView.repaint();
Log.d("Oncreate ", "if (mChartView != null)");
}
}
private void setChartSettings(XYMultipleSeriesRenderer renderer3,
String title, String xTitle, String yTitle, double xMin,
double xMax, double yMin, double yMax, int axesColor,
int labelsColor) {
// TODO Auto-generated method stub
renderer3.setChartTitle(title);
renderer3.setXTitle(xTitle);
renderer3.setYTitle(yTitle);
renderer3.setXAxisMin(xMin);
renderer3.setXAxisMax(xMax);
renderer3.setYAxisMin(yMin);
renderer3.setYAxisMax(yMax);
renderer3.setAxesColor(axesColor);
renderer3.setLabelsColor(labelsColor);
}
private XYMultipleSeriesRenderer buildRenderer(int[] colors,
PointStyle[] styles) {
// TODO Auto-generated method stub
XYMultipleSeriesRenderer renderer = new XYMultipleSeriesRenderer();
setRenderer(renderer, colors, styles);
return renderer;
}
private void setRenderer(XYMultipleSeriesRenderer renderer2, int[] colors,
PointStyle[] styles) {
// TODO Auto-generated method stub
renderer2.setAxisTitleTextSize(16);
renderer2.setChartTitleTextSize(20);
renderer2.setLabelsTextSize(15);
renderer2.setLegendTextSize(15);
renderer2.setPointSize(5f);
renderer2.setMargins(new int[] { 20, 30, 15, 20 });
int length = colors.length;
for (int i = 0; i < length; i++) {
XYSeriesRenderer r = new XYSeriesRenderer();
r.setColor(colors[i]);
r.setPointStyle(styles[i]);
renderer2.addSeriesRenderer(r);
}
}
private XYMultipleSeriesDataset mDataset(String[] titles,
List<double[]> xValues, List<double[]> yValues) {
// TODO Auto-generated method stub
XYMultipleSeriesDataset dataset1 = new XYMultipleSeriesDataset();
addXYSeries(dataset1, titles, xValues, yValues, 0);
return dataset1;
}
private void addXYSeries(XYMultipleSeriesDataset dataset, String[] titles,
List<double[]> xValues, List<double[]> yValues, int scale) {
// TODO Auto-generated method stub
int length = titles.length;
for (int i = 0; i < length; i++) {
XYSeries series = new XYSeries(titles[i], scale);
double[] xV = xValues.get(i);
double[] yV = yValues.get(i);
int seriesLength = xV.length;
for (int k = 0; k < seriesLength; k++) {
series.add(xV[k], yV[k]);
}
dataset.addSeries(series);
}
}
}
<RelativeLayout android:id="@+id/relativeLayout1"
android:layout_width="fill_parent" android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout android:id="@+id/linearLayout1"
android:background="@drawable/cricket" android:layout_alignParentLeft="true"
android:layout_height="wrap_content" android:layout_width="wrap_content"></LinearLayout>
<LinearLayout android:id="@+id/linearLayout2"
android:layout_below="@id/linearLayout1"
android:layout_alignParentLeft="true" android:layout_height="wrap_content"
android:layout_width="wrap_content"></LinearLayout>
</RelativeLayout>
答案 0 :(得分：1)
我现在无法在实践中测试这个，但我认为你错过了对
的调用 setContentView(R.layout.NAME_OF_YOUR_XML_FILE);
这可能是例如在这一行之后：
super.onCreate(savedInstanceState);
如果没有这个，layout变量为空，从而导致异常（我猜）。