Android上的空对象参考

Question

当我运行项目时，应用程序崩溃，并且打印出我的错误是NullPointerException，它是测试功能的参考。下面是与问题有关的类。

Tab1Values.java

public class Tab1Values extends Fragment {
    TextView tv1,tv2,tv3;
    int value=0,dbm=0;
    String ptype="",ntype="";
    public Tab1Values() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View v=inflater.inflate(R.layout.fragment_tab1, container, false);
        tv1=(TextView)v.findViewById(R.id.info);
        tv2=(TextView)v.findViewById(R.id.info2);
        tv3=(TextView)v.findViewById(R.id.info3);
        TelephonyManager tm=(TelephonyManager)getActivity().getSystemService(Context.TELEPHONY_SERVICE);
        ->tm.listen(new Tab1Signal2(this.getActivity()), PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);

        return v;
    }
    public void data(int value1,int value2){
        tv2.setText("GsmBitErrorRate:"+value1+" \nGsmSignalStrength:"+value2);
    }
    public void test(int LteSignalStrength,int LteRsrp,int LteRsrq,int LteRssnr,int LteCqi){
        tv3.setText("\nLteSignalStrength:"+dbm+" dbm"+
                "\nLteRsrp: "+LteRsrp+
                "\nLteRsrq: "+LteRsrq+
                "\nLteRssnr: "+LteRssnr+
                "\nLteCqi: "+ LteCqi);
    }
}

Tab1Signal2.java

public class Tab1Signal2 extends PhoneStateListener {
    Context mcontext;
    int LteSignalStrength=0,LteRsrp=0,LteRsrq=0,LteRssnr=0,LteCqi=0;
    int value1=0,value2=0,CdmaDbm=0,CdmaEcio=0,EvdoDbm=0,EvdoEcio=0,EvdoSnr=0;
    //int cid=0,lac=0,psc=0,statid=0,netid=0,sysid=0,lat=0,lon=0;
    String error,ss,val1,ccloc;
    private Tab1Values main;

    ->public Tab1Signal2(Context context){
        mcontext=context;
        //main=(Tab1Values) mcontext;
    }
    public void onSignalStrengthsChanged(SignalStrength signalStrength){
        super.onSignalStrengthsChanged(signalStrength);
        if (signalStrength.isGsm()) {
            value1=signalStrength.getGsmBitErrorRate();
            //error="\nGsmBitErrorRate:"+value1;
            value2=signalStrength.getGsmSignalStrength();
            //ss="\nGsmSignalStrength:"+value2;
            //main.data(value1,value2);
        }else if (signalStrength.getCdmaDbm() > 0) {
            CdmaDbm=signalStrength.getCdmaDbm();
            CdmaEcio=signalStrength.getCdmaEcio();
        } else {
            EvdoDbm=signalStrength.getEvdoDbm();
            EvdoEcio=signalStrength.getEvdoEcio();
            EvdoSnr=signalStrength.getEvdoSnr();
        }
        try {
            Method[] methods = android.telephony.SignalStrength.class
                    .getMethods();
            for (Method mthd : methods) {
                if (mthd.getName().equals("getLteSignalStrength")){
                    //val1=mthd.getName() ;
                    LteSignalStrength=(Integer)mthd.invoke(signalStrength);
                    //main.test(val2);
                }
                if (mthd.getName().equals("getLteRsrp")){
                    LteRsrp=(Integer)mthd.invoke(signalStrength);
                }
                if (mthd.getName().equals("getLteRsrq")){
                    LteRsrq=(Integer)mthd.invoke(signalStrength);
                }
                if (mthd.getName().equals("getLteRssnr")){
                    LteRssnr=(Integer)mthd.invoke(signalStrength);
                }
                if (mthd.getName().equals("getLteCqi")){
                    LteCqi=(Integer)mthd.invoke(signalStrength);
                }
                LINE 59 main.test(LteSignalStrength,LteRsrp,LteRsrq,LteRssnr,LteCqi);
            }
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }
}

我认为问题在于上下文构造函数在2个类之间的通信。在Tab1Signal2构造函数中，我注释了一行，并将其删除，因为它显示了错误，并且更具体地讲：{{ 1}}我在必须纠正的线条之前放了一个箭头，但找不到正确的方法。

Logcat

如果有人知道请帮忙。谢谢