Android：錯誤：java.lang.RuntimeException

Question

當我要去活動時，會發生錯誤。 這是LogCat

   01-16 12:22:17.014: E/AndroidRuntime(832): FATAL EXCEPTION: main
    01-16 12:22:17.014: E/AndroidRuntime(832): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.blackcat.triporganizer/com.blackcat.triporganizer.tracker.OthersBudgetActivity}: java.lang.NullPointerException
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.os.Handler.dispatchMessage(Handler.java:99)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.os.Looper.loop(Looper.java:137)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.ActivityThread.main(ActivityThread.java:5103)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at java.lang.reflect.Method.invokeNative(Native Method)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at java.lang.reflect.Method.invoke(Method.java:525)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at dalvik.system.NativeStart.main(Native Method)
    01-16 12:22:17.014: E/AndroidRuntime(832): Caused by: java.lang.NullPointerException
    01-16 12:22:17.014: E/AndroidRuntime(832):  at com.blackcat.triporganizer.tracker.OthersBudgetActivity.onCreate(OthersBudgetActivity.java:27)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.Activity.performCreate(Activity.java:5133)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
    01-16 12:22:17.014: E/AndroidRuntime(832):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
    01-16 12:22:17.014: E/AndroidRuntime(832):  ... 11 more

現在這是我想去的活動：

public class OthersBudgetActivity extends Activity {

    EditText BudgetInput;
    ImageButton DoneButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_others_budget);

        BudgetInput  = (EditText) findViewById(R.id.editText_EntertainmentBudget);
        BudgetInput.setInputType(InputType.TYPE_CLASS_NUMBER);

        DoneButton = (ImageButton) findViewById(R.id.imageButton_EntertainmentBudget);
        DoneButton.setOnClickListener(new OnClickListener() {           

              @Override
              public void onClick(View v) {


                    boolean didItWork = true;

                    TrackerDAO gettingInfo = new TrackerDAO(OthersBudgetActivity.this);



                    gettingInfo.open();

                    long getlastID = gettingInfo.getMaxID();

                    int prev_other = gettingInfo.getOtherPrev(getlastID);

                    String getAmountString = BudgetInput.getText().toString();

                    int getAmountInt = Integer.parseInt(getAmountString);

                    prev_other = prev_other + getAmountInt;

                    int prev_remainbudget = gettingInfo.getPrevRemainBudget(getlastID);

                    prev_remainbudget = prev_remainbudget - getAmountInt;

                    try{

                        gettingInfo.updatePrevRemainBudget(getlastID, prev_remainbudget);

                        gettingInfo.updateotherEntry(getlastID, prev_other);

                        gettingInfo.close();

                    }catch(Exception e){
                        didItWork = false;
                        Dialog d = new Dialog(OthersBudgetActivity.this);
                        d.setTitle("Not Updated");
                        d.show();
                    } finally {
                        if (didItWork) {
                            Dialog d = new Dialog(OthersBudgetActivity.this);
                            d.setTitle("Data Updated");
                            d.show();
                        }


                        Intent OpenActivity = new Intent (OthersBudgetActivity.this, BudgetTrackerActivity.class);
                        startActivity(OpenActivity);
                    }
              }
        });

    }

    @Override
    protected void onPause() {
        super.onPause();
        finish();
    }

}

謝謝。

Answer 1

您的onCreate（）中實際上沒有執行太多代碼，因此我猜您的Buttons為null，從而在訪問其方法或成員之一時導致此異常。

確保R.id.editText_EntertainmentBudget和R.id.imageButton_EntertainmentBudget是布局R.layout.activity_others_budget一部分。

Answer 2

根據我在Activity上使用NullExceptionPointers的經驗，即使它處於Intellisense預先輸入中，它也找不到資源。 最好的選擇是在調試時通過AVD運行它，然后您可以看到哪個對象為NULL（帶有斷點）。 有時會花費一些時間，但這會引導您找到答案。 我敢打賭這可能是您的EditText或Button引起了問題。