致命例外︰主

Question

大家好，这是我的第一个Android应用程序。我对Java和Eclipse很陌生，所以没有任何“noobity”。 我创建了这个项目，并尝试在我的设备上运行它（nexus s）。这就是我在LogCat中获得的。

12-17 21:03:11.550: E/AndroidRuntime(20786): FATAL EXCEPTION: main 
12-17 21:03:11.550: E/AndroidRuntime(20786): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gsmdata/com.example.gsmdata.GsmDataActivity}: java.lang.NullPointerException 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.app.ActivityThread.access$1500 (ActivityThread.java:117) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.os.Handler.dispatchMessage(Handler.java:99) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.os.Looper.loop(Looper.java:130) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.app.ActivityThread.main(ActivityThread.java:3683) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at java.lang.reflect.Method.invokeNative(Native Method) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at java.lang.reflect.Method.invoke(Method.java:507) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at dalvik.system.NativeStart.main(Native Method) 
12-17 21:03:11.550: E/AndroidRuntime(20786): Caused by: java.lang.NullPointerException 
12-17 21:03:11.550: E/AndroidRuntime(20786): at com.example.gsmdata.GsmDataActivity.onCreate(GsmDataActivity.java:72) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
12-17 21:03:11.550: E/AndroidRuntime(20786): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 
12-17 21:03:11.550: E/AndroidRuntime(20786): ... 11 more 

---

public class GsmDataActivity extends Activity { 
/** Called when the activity is first created. */ 

int[] SignalStrength = { 
     -113, 
     -111, 
     -109, 
     -107, 
     -105, 
     -103, 
     -101, 
     -99, 
     -97, 
     -95, 
     -93, 
     -91, 
     -89, 
     -87, 
     -85, 
     -83, 
     -81, 
     -79, 
     -77, 
     -75, 
     -73, 
     -71, 
     -69, 
     -67, 
     -65, 
     -63, 
     -61, 
     -59, 
     -57, 
     -55, 
     -53, 
     -51}; 

int network_type,signal_strength,cid,Lac,bts; 
TextView network, signal, ci, lac; 
TelephonyManager phone; 
GsmCellLocation cellId; 
CdmaCellLocation baseStation; 
SignalStrength phone_sig; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main);  

    network = (TextView) findViewById(R.id.tvNetwork); 
    signal =(TextView) findViewById(R.id.tvSignalValue); 
    ci = (TextView) findViewById(R.id.tvCiValue); 
    lac = (TextView) findViewById(R.id.tvLacValue); 

    network_type=phone.getNetworkType(); 

    switch (network_type){ 

    case 1: network.setText("GPRS"); 
    case 3: network.setText("UMTS"); 
    case 4: network.setText("CDMA"); 
    case 8: network.setText("HSDPA"); 
    case 9: network.setText("HSUPA"); 
    case 10: network.setText("HSPA"); 
    case 13: network.setText("LTE"); 
    default: network.setText("UNKNOWN");  

    } 

    if (network_type==1){ 
     signal_strength = phone_sig.getGsmSignalStrength(); 
     signal.setText(SignalStrength[signal_strength] + "dBm"); 
     cid= cellId.getCid(); 
     Lac=cellId.getLac(); 
    } 
    else if(network_type==0){ 
     signal.setText("Unknown Network type"); 
    } 
    else{ 
     signal_strength= phone_sig.getCdmaDbm(); 
     signal.setText(SignalStrength[signal_strength] + "dBm"); 
     bts= baseStation.getBaseStationId(); 
     Lac=cellId.getLac(); 
    } 


} 



} 

这是我的Java类。我主要得到一个致命的例外。我不知道为什么。你可以帮我吗。先谢谢你。以下是XML代码：

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:orientation="vertical" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" 
> 

<TextView 
android:layout_width= "fill_parent" 
android:layout_height="wrap_content" 
android:textSize="50dp" 
android:paddingBottom="5dp" 
android:id="@+id/tvNetwork" 
></TextView> 
<TextView 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:text="@string/strength" 
android:layout_gravity="center" 
    android:paddingBottom="5dp" 
android:id="@+id/tvSignal" 
/> 
<TextView 
android:layout_width= "fill_parent" 
android:layout_height="wrap_content" 
android:textSize="50dp" 
android:paddingBottom="5dp" 
android:gravity="center" 
android:id="@+id/tvSignalValue" 
></TextView> 
<TextView 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:text="@string/cellid" 
android:layout_gravity="center" 
android:paddingBottom="5dp" 
android:id="@+id/tvCi" 
/> 
<TextView 
android:layout_width= "fill_parent" 
android:layout_height="wrap_content" 
android:textSize="50dp" 
android:paddingBottom="5dp" 
android:gravity="center" 
android:id="@+id/tvCiValue" 
></TextView> 
<TextView 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:text="@string/lac" 
android:layout_gravity="center" 
android:id="@+id/tvLac" 
/> 
<TextView 
android:layout_width= "fill_parent" 
android:layout_height="wrap_content" 
android:textSize="50dp" 
android:paddingBottom="5dp" 
android:gravity="center" 
android:id="@+id/tvLacValue" 
></TextView>  
</LinearLayout> 

Answer 1

phone为空当你调用phone.getNetworkType();，所以你得到的NullPointerException。

第一分配telephonty经理吧：

phone = getSystemService(Context.TELEPHONY_SERVICE); 
phone.getNetworkType();