如何使用CellIdentityGsm

Question

我试图使用以下代码来使用CellIdentityGsm：

final TelephonyManager tm = (TelephonyManager) getSystemService(TELEPHONY_SERVICE);
    CellInfoGsm cellInfoGsm = (CellInfoGsm) tm.getAllCellInfo().get(0);
    CellIdentityGsm cellIdentityGsm = cellInfoGsm.getCellIdentity();
    int MCC = cellIdentityGsm.getMcc();


    TextView view = null;
    view = (TextView) findViewById(R.id.mCC);
    view.setText("MCC: " + MCC);

它在模拟器上工作，但对于实际设备，应用程序会崩溃。API级别可以，权限也可以。

***********************Log|cat******************

    02-17 21:06:02.546  12608-12608/com.demo.aem.trial_1 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.demo.aem.trial_1, PID: 12608
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.demo.aem.trial_1/com.demo.aem.trial_1.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2350)
            at android.app.ActivityThread.access$800(ActivityThread.java:163)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1257)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5335)
            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:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.demo.aem.trial_1.MainActivity.onCreate(MainActivity.java:31)
            at android.app.Activity.performCreate(Activity.java:5389)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2256)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2350)
            at android.app.ActivityThread.access$800(ActivityThread.java:163)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1257)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5335)
            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:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)
02-17 21:06:04.236  12608-12608/com.demo.aem.trial_1 I/Process﹕ Sending signal. PID: 12608 SIG: 9

Answer 1

这是一个正确的想法。我注意到您有一个空指针异常。这意味着很可能在这条线上，

CellInfoGsm cellInfoGsm = (CellInfoGsm) tm.getAllCellInfo().get(0);

当您转换为(CellInfoGSM)时，实际上tm.getAllCellInfo().get(0);可能不是CellInfoGSM，但可能是WCDMA或CDMA。

所以，也许cellInfoGsm是空的。

我可以建议you....to首先检查tm.getAllCellInfo().get(0);是否是GSM、WCDMA或CDMA，然后再将其转换为变量。