AltBeacon 应用程序在 Android 选项卡上崩溃

Question

我一直在尝试使用 AltBeacon 监控示例代码来监控我的 Kontakt.io 信标，如http://altbeacon.github.io/android-beacon-library/samples.html 此处所述。我可以在我的android studio（1.0.2）中导入库（android-beacon-library-2.1.3.aar）并且监控代码没有错误。但是当我想在我的选项卡（LG Tab 7 API 19）上运行它时，它会停止处理屏幕上的消息。 当我在 MainActivity.java 中使用 import. 时，我可以确定 Altbeacon 库已成功导入，因为它出现在列表中。我没有以任何方式更改代码。 Logcat 说：

11988-11988/xxx.altbeeklibtest1 W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41747e48)
11988-11988/xxxx.altbeeklibtest1 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: xxxx.altbeeklibtest1, PID: 11988
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{xxxx.altbeeklibtest1/xxxx.altbeeklibtest1.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2252)
            at android.app.ActivityThread.access$800(ActivityThread.java:139)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5103)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:606)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at android.content.ContextWrapper.getPackageManager(ContextWrapper.java:94)
            at org.altbeacon.beacon.BeaconManager.verifyServiceDeclaration(BeaconManager.java:707)
            at org.altbeacon.beacon.BeaconManager.<init>(BeaconManager.java:233)
            at org.altbeacon.beacon.BeaconManager.getInstanceForApplication(BeaconManager.java:211)
            at com.example.shaffat.altbeeklibtest1.MainActivity.<init>(MainActivity.java:18)
            at java.lang.Class.newInstanceImpl(Native Method)
            at java.lang.Class.newInstance(Class.java:1208)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2119)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2252)
            at android.app.ActivityThread.access$800(ActivityThread.java:139)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5103)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:606)
            at dalvik.system.NativeStart.main(Native Method)

我做错了什么？非常感谢帮助

Answer 1

示例以这种方式初始化beaconManager：

private BeaconManager beaconManager = beaconManager.getInstanceForApplication(this);

您应该在 Activity 的 onCreate() 方法中执行此操作。

public class MainActivity extends Activity  implements BeaconConsumer{
    protected static final String TAG = "RangingActivity";
    private BeaconManager;

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
       beaconManager = BeaconManager.getInstanceForApplication(this);
       beaconManager.getBeaconParsers().add(new BeaconParser().setBeaconLayout("m:2-3=0216,i:4-19,i:20-21,i:22-23,p:24-24"));
         // set the duration of the scan to be 1.1 seconds
        beaconManager.setBackgroundScanPeriod(1100l); 
        // set the time between each scan to be 1 hour (3600 seconds)
        beaconManager.setBackgroundBetweenScanPeriod(1000);

        beaconManager.bind(this);

    }

Answer 2

我需要查看调用BeaconManager.getInstanceForApplication(context) 的代码才能确定，但​​堆栈跟踪表明此代码正在接收空上下文。传递的上下文必须是 Activity、Application 或 Service 的非 null 有效实例。