Question

我被困住了，一双新眼睛会受到赞赏。我MainActivity点击fragment点击button database。它把它拉得很好，然后我在fragment中添加了public class StatsFragment extends Fragment { public static MySmokinDatabase mySmokinDatabase; public static Model model; View view; public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { model = MainActivity.model; mySmokinDatabase = new MySmokinDatabase(getActivity()); TextView daysText = (TextView) getView().findViewById(R.id.days); TextView totalText = (TextView) getView().findViewById(R.id.total); TextView aveText = (TextView) getView().findViewById(R.id.ave); try { daysText.setText("" + (model.getDays())); totalText.setText("" + mySmokinDatabase.getTotal()); if (model.getDays() > 0) aveText.setText("" + (float) mySmokinDatabase.getTotal() / (float) model.getDays()); } catch (Exception e) { Log.v("*** DEBUG ***", "Error"); System.out.print("error" + e); } // Create, or inflate the Fragment’s UI, and return it. // If this Fragment has no UI then return null. view = inflater.inflate(R.layout.stats_frag, container, false); return view; } }次调用，现在它已经崩溃了。在我的logcat中，它说我在onCreate中得到一个空指针异常。这是代码和logcat。

片段代码

public void statisticsHandler(View view) {
    FragmentManager fm = getFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();
    Log.v("*** DEBUG ***", "Statistics Handler");
    ft.replace(R.id.main_container_Id, new StatsFragment());
    ft.commit();
}

按钮处理程序

03-27 15:40:03.767: W/dalvikvm(862): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
03-27 15:40:03.867: E/AndroidRuntime(862): FATAL EXCEPTION: main
03-27 15:40:03.867: E/AndroidRuntime(862): java.lang.NullPointerException
03-27 15:40:03.867: E/AndroidRuntime(862):  at com.example.smokin4tomsullivan.StatsFragment.onCreateView(StatsFragment.java:24)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:829)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1035)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.app.BackStackRecord.run(BackStackRecord.java:635)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1397)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.os.Handler.handleCallback(Handler.java:615)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.os.Handler.dispatchMessage(Handler.java:92)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.os.Looper.loop(Looper.java:137)
03-27 15:40:03.867: E/AndroidRuntime(862):  at android.app.ActivityThread.main(ActivityThread.java:4745)
03-27 15:40:03.867: E/AndroidRuntime(862):  at java.lang.reflect.Method.invokeNative(Native Method)
03-27 15:40:03.867: E/AndroidRuntime(862):  at java.lang.reflect.Method.invoke(Method.java:511)
03-27 15:40:03.867: E/AndroidRuntime(862):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
03-27 15:40:03.867: E/AndroidRuntime(862):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-27 15:40:03.867: E/AndroidRuntime(862):  at dalvik.system.NativeStart.main(Native Method)

logcat的

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Answer 1

在获取您的观看之前设置此view = inflater.inflate(R.layout.stats_frag, container, false);

获取视图时使用getActivity()代替getView()。

即

   TextView daysText = (TextView) getActivity().findViewById(R.id.days); 
    TextView totalText = (TextView)  getActivity().findViewById(R.id.total); 
    TextView aveText = (TextView) getActivity().findViewById(R.id.ave);

Answer 2

在抓取视图之前将其移近顶部。您正在获取NPE，因为findViewById调用返回null。

// Create, or inflate the Fragment’s UI, and return it.
// If this Fragment has no UI then return null.
view = inflater.inflate(R.layout.stats_frag, container, false);

在抓住视图之前

。然后做

TextView daysText = (TextView) view.findViewById(R.id.days); 
TextView totalText = (TextView) view.findViewById(R.id.total); 
TextView aveText = (TextView) view.findViewById(R.id.ave);

Android碎片从NPE onCreate崩溃

2 个答案: