Question

我在我的Fragment课程中使用了这部分代码来显示wifi频道图表，问题是当我从第一个Fragment更改为第二个Fragment应用程序因崩溃而崩溃时Receiver上的错误可以帮助我吗

public class Receiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {

        WifiManager wifiMan=(WifiManager)getActivity().getSystemService(Context.WIFI_SERVICE);
          wifiMan.startScan();

        int length;
        List<ScanResult> results = wifiManager.getScanResults();


        if (intent.getAction().equals(
                WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)) {
            results = wifiManager.getScanResults();
            length = results.size();

            Log.i("length1", length + "");
            XYMultipleSeriesRenderer renderer = getTruitonBarRenderer(results
                    .size());
            myChartSettings(renderer);

            chartLayout = (FrameLayout) getActivity().findViewById(
                    R.id.chart);
            GraphicalView mChartView = ChartFactory.getBarChartView(
                    getActivity(), getTruitonBarDataset(results), renderer,
                    Type.STACKED);

            if (mChartView != null) {
                chartLayout.removeView(mChartView);
            }


            chartLayout.addView(mChartView, 0, new LayoutParams(
                    LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));             
        }

    }
}

这是我的logcat输出：

06-17 14:36:50.778: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:36:50.778: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:36:51.799: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:36:51.799: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:36:55.012: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:36:55.012: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:36:59.167: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:36:59.167: E/SpannableStringBuilder(10263): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
06-17 14:37:16.575: E/AndroidRuntime(10263): FATAL EXCEPTION: main
06-17 14:37:16.575: E/AndroidRuntime(10263): java.lang.RuntimeException: Error receiving broadcast Intent { act=android.net.wifi.SCAN_RESULTS flg=0x8000010 } in com.esprit.testproject.apscan.GraphFragment$Receiver@423df448
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:765)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.os.Handler.handleCallback(Handler.java:615)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.os.Looper.loop(Looper.java:137)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.app.ActivityThread.main(ActivityThread.java:4867)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at java.lang.reflect.Method.invokeNative(Native Method)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at java.lang.reflect.Method.invoke(Method.java:511)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at dalvik.system.NativeStart.main(Native Method)
06-17 14:37:16.575: E/AndroidRuntime(10263): Caused by: java.lang.NullPointerException
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.view.ViewConfiguration.get(ViewConfiguration.java:332)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.view.View.<init>(View.java:3304)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at org.achartengine.GraphicalView.<init>(GraphicalView.java:91)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at org.achartengine.ChartFactory.getBarChartView(ChartFactory.java:164)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at com.esprit.testproject.apscan.GraphFragment$Receiver.onReceive(GraphFragment.java:356)
06-17 14:37:16.575: E/AndroidRuntime(10263):    at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:755)
06-17 14:37:16.575: E/AndroidRuntime(10263):    ... 9 more

Answer 1

您在NullPointerException的通话中获得ChartFactory.getBarChartView。因此，您可能想要检查您传递的参数之一是null。

我怀疑在某些情况下，两个电话getTruitonBarRenderer()和getTruitonBarDataset()中的一个会返回null。（也许当WiFi扫描没有返回结果？）添加一些逻辑来处理这些情况，你应该很好。

但是，我现在也看到你以奇怪的方式处理mChartView。

您将mChartView声明为本地变量。示例代码将其作为类成员，因此其内容将在调用之间保留。
示例代码在重新分配chartLayout.removeView(mChartView)之前调用mChartView ，从而在创建之前从布局中删除旧视图（在上次调用方法时创建）插入一个新的。在上面发布的代码中，对chartLayout.removeView(mChartView)的调用将删除一个从未插入的布局，这可能会引发异常或者什么都不做。

尝试替换这段代码

GraphicalView mChartView = ChartFactory.getBarChartView( getActivity(), getTruitonBarDataset(results), renderer, Type.STACKED); if (mChartView != null) { chartLayout.removeView(mChartView); } chartLayout.addView(mChartView, 0, new LayoutParams( LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));

与

XYMultipleSeriesDataset dataset = getTruitonBarDataset(results); if ((dataset != null) && (renderer != null)) { if (mChartView != null) { chartLayout.removeView(mChartView); } GraphicalView mChartView = ChartFactory.getBarChartView( getActivity(), dataset, renderer, Type.STACKED); chartLayout.addView(mChartView, 0, new LayoutParams( LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)); }

并另外向您的班级添加mChartView成员。

WiFi频道图广播接收器

1 个答案: