Application throws a NullPointerException

I created 3 Activities.

1. ElecBillActivity

2. AddBillActivity

3. ResultActivity

I successfully enterd into the second Activity using an Intent but as soon as I click the Submit button in the second Activity, I am getting an exception.

I tried many ways but I am unable to understand the problem.

This is my 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/开发者_如何学CAndroidRuntime(  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

I am also providing the link for my code.

As my problem seems to big and my class files are too big I provided the download link here.

As I am a new user I am unable to post the screenshots here.

According to the logs you got a NullPointerException in ResultActivity.java on line 21... taking a look into your source code, this is caused by calling getIntent() which is a member function of Activity which can only be called after the Activity is created. Therefore, move your initialization code into the onCreate method.

Change your member definitions to:

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;

Further on you are calling getIntent().getExtras() and store it in the variable bundle. But as you never put any extras in your Intent in AddBillActivity, bundle will be null and when you try bundle.getString(...) it will throw another NullPointerException!

First change to make is to give an android:id attribute to your RadioGroup in the form.xml file. Set it to radios and add the this line to your member variables in AddBillActivity:

public static RadioGroup radios;

As well as this line to the setUpViews method:

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

Then change the addTask method in AddBillActivity to

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);

And now you can get all those extras in your onCreate method in ResultActivity:

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));

This should do it ;)