应用程序抛出NullPointerException

时间：2011-04-07 10:02:18

标签： android

我创建了3个活动。

  1. ElecBillActivity

  2. AddBillActivity

  3. ResultActivity

    4. 我使用Intent成功进入第二个Activity，但是当我点击第二个Activity中的Submit按钮时，我收到了异常。

    我尝试了很多方法，但我无法理解这个问题。

    这是我的logcat 

    E/AndroidRuntime(  506): FATAL EXCEPTION: main
E/AndroidRuntime(  506): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.sai.android.billing/com.sai.android.billing.ResultActivity}: java.lang.NullPointerException
E/AndroidRuntime(  506):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1544)
E/AndroidRuntime(  506):        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1638)
E/AndroidRuntime(  506):        at android.app.ActivityThread.access$1500(ActivityThread.java:117)
E/AndroidRuntime(  506):        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:928)
E/AndroidRuntime(  506):        at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(  506):        at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime(  506):        at android.app.ActivityThread.main(ActivityThread.java:3647)
E/AndroidRuntime(  506):        at java.lang.reflect.Method.invokeNative(NativeMethod)
E/AndroidRuntime(  506):        at java.lang.reflect.Method.invoke(Method.java:507)
E/AndroidRuntime(  506):        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
E/AndroidRuntime(  506):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E/AndroidRuntime(  506):        at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(  506): Caused by: java.lang.NullPointerException
E/AndroidRuntime(  506):        at com.sai.android.billing.ResultActivity.<init>(ResultActivity.java:21)
E/AndroidRuntime(  506):        at java.lang.Class.newInstanceImpl(Native Method)
E/AndroidRuntime(  506):        at java.lang.Class.newInstance(Class.java:1409)
E/AndroidRuntime(  506):        at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
E/AndroidRuntime(  506):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1536)
E/AndroidRuntime(  506):        ... 11 more
W/ActivityManager(   70):   Force finishing activity com.sai.android.billing/.ResultActivity
W/ActivityManager(   70):   Force finishing activity com.sai.android.billing/.AddBillActivity
W/ActivityManager(   70): Activity pause timeout for HistoryRecord{4079d8f8 com.sai.android.billing/.ResultActivity}
I/ARMAssembler(   70): generated scanline__00000177:03515104_00001001_00000000 [91 ipp] (114 ins) at [0x445b36e0:0x445b38a8] in 1634844 ns
I/Process (  506): Sending signal. PID: 506 SIG: 9
I/ActivityManager(   70): Process com.sai.android.billing (pid 506) has died.
E/InputDispatcher(   70): channel '4060e840 com.sai.android.billing/com.sai.android.billing.ElecBillingActivity (server)' ~ Consumer closed input channel or an error occurred.  events=0x8
E/InputDispatcher(   70): channel '4060e840 com.sai.android.billing/com.sai.android.billing.ElecBillingActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
I/WindowManager(   70): WIN DEATH: Window{4060e840 com.sai.android.billing/com.sai.android.billing.ElecBillingActivity paused=false}
I/WindowManager(   70): WIN DEATH: Window{406f4868 com.sai.android.billing/com.sai.android.billing.AddBillActivity paused=true}
E/InputDispatcher(   70): Received spurious receive callback for unknown input channel.  fd=151, events=0x8
W/InputManagerService(   70): Got RemoteException sending setActive(false) notification to pid 506 uid 10038

    我还提供了code的链接。

    由于我的问题似乎很大而我的班级文件太大，我在这里提供了下载链接 由于我是新用户，因此无法在此处发布屏幕截图。

1 个答案:

答案 0 :(得分：4)

根据日志，您在第21行的NullPointerException中获得ResultActivity.java ...查看您的源代码，这是由调用getIntent()成员函数引起的Activity的{​​{1}}只能在Activity创建后调用。因此，请将初始化代码移到onCreate方法中。

将您的成员定义更改为：

private TextView resultOk;
int highLimit,lowLimit,highRate,lowRate,defaultRate,amount;
Bundle bundle;
String userName;
String meterNumber;
String prevReading;
String currReading;
int pR;
int cR;
int units;
String u;
String a;

此外，您正在调用getIntent().getExtras()并将其存储在变量bundle中。但是，由于您从未在Intent AddBillActivity bundle中添加任何额外内容，null将为bundle.getString(...)，当您尝试NullPointerException时，它会抛出另一个android:id RadioGroup }！

要做的第一个更改是在form.xml文件中为radios提供AddBillActivity属性。将其设置为public static RadioGroup radios; ，并将此行添加到setUpViews中的成员变量：

radios = (RadioGroup)findViewById(R.id.radios);

以及addTask方法的这一行：

AddBillActivity

然后将Intent intent1 = new Intent(AddBillActivity.this, ResultActivity.class); intent1.putExtra("bill_name", billNameEditText.getText().toString()); intent1.putExtra("bill_number", billNumEditText.getText().toString()); intent1.putExtra("bill_previous", billPrevEditText.getText().toString()); intent1.putExtra("bill_current", billCurrEditText.getText().toString()); intent1.putExtra("radio", radios.getCheckedRadioButtonId()); startActivity(intent1); 中的onCreate方法更改为

ResultActivity

现在，您可以使用bundle = getIntent().getExtras(); userName = bundle.getString("bill_name"); meterNumber = bundle.getString("bill_number"); prevReading = bundle.getString("bill_previous"); currReading = bundle.getString("bill_current"); pR = Integer.parseInt(prevReading); cR = Integer.parseInt(currReading); units = pR - cR; u = bundle.getString(String.valueOf(units)); a = bundle.getString(String.valueOf(units)); 中的{{1}}方法获取所有额外内容：

{{1}}

这应该这样做;）

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