空指針異常 - 片段活動

我對此很新，並設法獲取我的應用程序的佈局，並使用製表符和片段。空指針異常 - 片段活動

每個佈局是一個不同的計算器，需要不同的計算才能運行。我正在努力弄清楚如何做到這一點。任何幫助，非常感謝。

我想要開始工作的第一件事是BMI片段的spinnersetup。我是在MainActivity還是Fragment中執行此操作？從我迄今爲止所做的工作中，我得到一個空指針異常。

這裏是我的MainActivity代碼：

public Fragment getItem(int position) { 
      // getItem is called to instantiate the fragment for the given page. 
      // Return a DummySectionFragment (defined as a static inner class 
      // below) with the page number as its lone argument. 
      switch (position) { 
      case 0: 
       Fragment fragment = new DummySectionFragment(); 
       Bundle args = new Bundle(); 
       args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1); 
       fragment.setArguments(args); 
       return fragment; 

       case 1: 
       Fragment fragment1 = new DummySectionFragment1(); 
       Bundle args1 = new Bundle(); 
       args1.putInt(DummySectionFragment1.ARG_SECTION_NUMBER, position + 2); 
       fragment1.setArguments(args1); 
       return fragment1; 

       case 2: 

       Fragment fragment2 = new DummySectionFragment2(); 
       Bundle args2 = new Bundle(); 
       args2.putInt(DummySectionFragment2.ARG_SECTION_NUMBER, position + 3); 
       fragment2.setArguments(args2); 
       return fragment2; 

       case 3: 

        Fragment fragment3 = new DummySectionFragment3(); 
        Bundle args3 = new Bundle(); 
        args3.putInt(DummySectionFragment3.ARG_SECTION_NUMBER, position + 4); 
        fragment3.setArguments(args3); 
        return fragment3; 

      default: 
       return null; 
      } 
     } 

     @Override 
     public int getCount() { 
      // Show 4 total pages. 
      return 4; 
     } 

     @Override 
     public CharSequence getPageTitle(int position) { 
      Locale l = Locale.getDefault(); 
      switch (position) { 
      case 0: 
       return getString(R.string.title_section1).toUpperCase(l); 
      case 1: 
       return getString(R.string.title_section2).toUpperCase(l); 
      case 2: 
       return getString(R.string.title_section3).toUpperCase(l); 
      case 3: 
       return getString(R.string.title_section4).toUpperCase(l); 
      } 
      return null; 
     } 
    } 

}

我的代碼片段：

package com.HealthKicks.bodystats.admob; 

import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AdapterView; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.Spinner; 

public class DummySectionFragment extends Fragment { 

    EditText height_edit_text1, weight_edit_text1, height, weight; 
    Spinner height_spinner, weight_spinner; 
    Button calculatebmi; 

    public static final String ARG_SECTION_NUMBER = "section_number"; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
      Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.bmi, container, false); 

     setupSpinners(); 

     height_spinner =(Spinner) getView().findViewById(R.id.height_spinner); 
     weight_spinner =(Spinner) getView().findViewById(R.id.weight_spinner); 
     height_edit_text1 =(EditText) getView().findViewById(R.id.height_edit_text1); 
     weight_edit_text1 =(EditText) getView().findViewById(R.id.weight_edit_text1); 
     weight_spinner =(Spinner) getView().findViewById(R.id.weight_spinner); 

     return rootView; 
    } 


    void setupSpinners() { 

     height_spinner =(Spinner) getView().findViewById(R.id.height_spinner); 
     weight_spinner =(Spinner) getView().findViewById(R.id.weight_spinner); 
     height_edit_text1 =(EditText) getView().findViewById(R.id.height_edit_text1); 
     weight_edit_text1 =(EditText) getView().findViewById(R.id.weight_edit_text1); 

     // TODO Auto-generated method stub 
      height_spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() { 

      @Override 
      public void onItemSelected(AdapterView<?> parent, View view, int position, long id) { 
       if (position == 0){ 
        height_edit_text1.setVisibility(View.GONE); 
       } else { 
        height_edit_text1.setVisibility(View.VISIBLE); 
       } 
      } 

      @Override 
      public void onNothingSelected(AdapterView<?> parent) { 

      } 
     }); 
       weight_spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() { 
        @Override 
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) { 
         if (position == 0){ 
          weight_edit_text1.setVisibility(View.GONE); 
         } 
         else if (position == 1){ 
          weight_edit_text1.setVisibility(View.GONE); 
         } 
         else { 
          weight_edit_text1.setVisibility(View.VISIBLE); 
         } 
        } 

        @Override 
        public void onNothingSelected(AdapterView<?> parent) { 

        } 
       }); 
    } 
}

的logcat：

10-10 18:38:40.959: E/AndroidRuntime(1118): FATAL EXCEPTION: main 
10-10 18:38:40.959: E/AndroidRuntime(1118): java.lang.NullPointerException 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at com.HealthKicks.bodystats.admob.DummySectionFragment.setupSpinners(DummySectionFragment.java:33) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at com.HealthKicks.bodystats.admob.DummySectionFragment.onCreateView(DummySectionFragment.java:26) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.app.Fragment.performCreateView(Fragment.java:1478) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.view.ViewPager.populate(ViewPager.java:1068) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.view.ViewPager.populate(ViewPager.java:914) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.View.measure(View.java:15848) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.View.measure(View.java:15848) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:302) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.View.measure(View.java:15848) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2189) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.View.measure(View.java:15848) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1905) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1104) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1284) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.Choreographer.doCallbacks(Choreographer.java:562) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.Choreographer.doFrame(Choreographer.java:532) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.os.Handler.handleCallback(Handler.java:730) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.os.Handler.dispatchMessage(Handler.java:92) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.os.Looper.loop(Looper.java:137) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at android.app.ActivityThread.main(ActivityThread.java:5103) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at java.lang.reflect.Method.invokeNative(Native Method) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at java.lang.reflect.Method.invoke(Method.java:525) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
10-10 18:38:40.959: E/AndroidRuntime(1118):  at dalvik.system.NativeStart.main(Native Method)

來源

2013-10-10 user2753285

問題和標題不匹配..編輯的問題正確 – Shubhank

發表您的logcat也.. – QuokMoon

什麼是BMI片段？你可以發佈你的佈局截圖。我不明白getItem方法是什麼... – user1685095

變化onCreateView從這個：

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.bmi, container, false); 
    setupSpinners(); 
    height_spinner = (Spinner) getView().findViewById(R.id.height_spinner); 
    weight_spinner = (Spinner) getView().findViewById(R.id.weight_spinner); 
    height_edit_text1 = (EditText) getView().findViewById(R.id.height_edit_text1); 
    weight_edit_text1 = (EditText) getView().findViewById(R.id.weight_edit_text1); 
    weight_spinner = (Spinner) getView().findViewById(R.id.weight_spinner); 
    return rootView; 
}

這樣：

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.bmi, container, false); 
    height_spinner = (Spinner) rootView.findViewById(R.id.height_spinner); 
    weight_spinner = (Spinner) rootView.findViewById(R.id.weight_spinner); 
    height_edit_text1 = (EditText) rootView.findViewById(R.id.height_edit_text1); 
    weight_edit_text1 = (EditText) rootView.findViewById(R.id.weight_edit_text1); 
    weight_spinner = (Spinner) rootView.findViewById(R.id.weight_spinner); 
    return rootView; 
}

呼叫setupSpinners從onViewCreated：

@Override 
public void onViewCreated(View view, Bundle savedInstanceState) { 
    super.onViewCreated(view, savedInstanceState); 
    setupSpinners(); 
}

，如果你傳遞view爲參數，所以不要叫每次getView()這將是更有效的：

來源

2013-10-11 15:29:10 gunar

您正在運行的所有成員的初始化兩次。

在onCreateView()的正文中，您可以調用setupSpinners();初始化您的成員，然後重新初始化它們。只在一個地方初始化它們。

來源

2013-10-10 18:59:23 gh123man

感謝您的反饋，我現在已經做到了，但仍然得到相同的logcat錯誤。 – user2753285

你能否用更新後的代碼更新你的文章？ – gh123man

我已經使用我更新的片段代碼更新了帖子。 – user2753285

您的DummySectionFragment中未初始化任何視圖。你必須告訴什麼是每個微調，是這樣的：

height_spinner = (Spinner) getView().findViewById(R.id.theIdInTheLayoutFile);

來源

2013-10-10 22:59:23

感謝您的反饋，我現在已經做到了，但仍然得到相同的logcat錯誤。 – user2753285

現在，您在onCreate視圖方法中調用「getView（）」。該視圖尚未創建！您必須在您的設置方法中刪除初始化，並在onCreateView方法中將「getView（）」替換爲「rootView」。這是您正在查找的視圖的一個實例。 –

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.bmi, container, false); 
    height_spinner = (Spinner) rootView.findViewById(R.id.height_spinner); 
    weight_spinner = (Spinner) rootView.findViewById(R.id.weight_spinner); 
    height_edit_text1 = (EditText) rootView.findViewById(R.id.height_edit_text1); 
    weight_edit_text1 = (EditText) rootView.findViewById(R.id.weight_edit_text1); 
    weight_spinner = (Spinner) rootView.findViewById(R.id.weight_spinner); 

    setUpSpinners(rootView); 
    return rootView; 
} 

protected void setUpSpinners(pass rootview here...) 
{ 
     ...use spinners as 
     Spinner weight_spinner = (Spinner) rootView.findViewById(R.id.weight_spinner); 
}

來源

2014-03-21 19:38:50

空指針異常 - 片段活動

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