새로운 액티비티를 시작할 때 NPE가 throw됩니다.

-1

다음 코드는 앱의 UI 껍데기에 불과합니다. successfuly로드하지만 MainActivity - "Create Plot"버튼이 CreatePlotActivity를 시작해야 할 때 - 다음 액티비티를 시작하지 않고 앱이 충돌합니다. 대신 NPE가 던져집니다. 다음은 모든 관련 파일입니다. 참고 MainActivity.java새로운 액티비티를 시작할 때 NPE가 throw됩니다.

package com.example.probaddieweaponplotter; 

import android.app.Activity; 
import android.content.Intent; 
import android.os.Bundle; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 

public class MainActivity extends Activity implements OnClickListener { 

    Button button; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) {   
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.activity_main);  
     button = (Button) findViewById(R.id.button_create_plot); 
     button.setOnClickListener(this); 
    } 

    @Override 
    public void onClick(View v) {     
     Intent intent = new Intent(this, CreatePlotActivity.class); 
     startActivity(intent); 
    } 
}

CreatePlotActivity.java

package com.example.probaddieweaponplotter; 

import android.app.Activity; 
import android.os.Bundle; 

public class CreatePlotActivity extends Activity { 

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

PlotOptionsListFragment.java

,745,151

로그 캣

04-02 02:33:53.005: E/AndroidRuntime(13555): FATAL EXCEPTION: main 
04-02 02:33:53.005: E/AndroidRuntime(13555): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.probaddieweaponplotter/com.example.probaddieweaponplotter.CreatePlotActivity}: java.lang.NullPointerException 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.os.Handler.dispatchMessage(Handler.java:99) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.os.Looper.loop(Looper.java:137) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.ActivityThread.main(ActivityThread.java:5041) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at java.lang.reflect.Method.invokeNative(Native Method) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at java.lang.reflect.Method.invoke(Method.java:511) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at dalvik.system.NativeStart.main(Native Method) 
04-02 02:33:53.005: E/AndroidRuntime(13555): Caused by: java.lang.NullPointerException 
04-02 02:33:53.005: E/AndroidRuntime(13555): at com.example.probaddieweaponplotter.PlotOptionsListFragment.onActivityCreated(PlotOptionsListFragment.java:33) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.Fragment.performActivityCreated(Fragment.java:1703) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:903) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1057) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1039) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1840) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.Activity.performCreate(Activity.java:5107) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
04-02 02:33:53.005: E/AndroidRuntime(13555): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
04-02 02:33:53.005: E/AndroidRuntime(13555): ... 11 more

: 라인 33의 CreateOptionsFragment list.setAdapter(adapter) 인 5,

package com.example.probaddieweaponplotter; 

import java.util.ArrayList; 

import android.app.Fragment; 
import android.content.Context; 
import android.content.res.Resources; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.ListView; 
import android.widget.TextView; 

public class PlotOptionsListFragment extends Fragment { 

    ListView listView; 

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


    } 

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onActivityCreated(savedInstanceState); 
     listView = (ListView) getActivity().findViewById(R.id.plot_options_listView);  
     MyAdapter adapter = new MyAdapter(getActivity()); 
     listView.setAdapter(adapter);   
    } 

} 

class MyAdapter extends BaseAdapter { 

    ArrayList<PlotOptionsListItem> list; 
    Context context; 

    public MyAdapter(Context context) { 
     // TODO Auto-generated constructor stub 
     this.context = context; 
     list = new ArrayList<PlotOptionsListItem>(); 

     Resources res = context.getResources(); 
     String[] items = res.getStringArray(R.array.plot_options_list_items); 
     String[] descriptions = res.getStringArray(R.array.plot_options_list_descriptions); 

     for (int i = 0; i < items.length; i++) { 
      list.add(new PlotOptionsListItem(items[i], descriptions[i])); 
     } 
    } 

    @Override 
    public int getCount() { 
     // TODO Auto-generated method stub 
     return list.size(); 
    } 

    @Override 
    public Object getItem(int position) { 
     // TODO Auto-generated method stub 
     return list.get(position); 
    } 

    @Override 
    public long getItemId(int position) { 
     // TODO Auto-generated method stub 
     return position; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     // TODO Auto-generated method stub 
     LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
     View row = inflater.inflate(R.layout.plot_options_list_single_item, parent, false); 
     TextView item = (TextView) row.findViewById(R.id.plot_options_list_item_text); 
     TextView description = (TextView) row.findViewById(R.id.plot_options_list_desc_text); 

     PlotOptionsListItem temp = list.get(position); 

     item.setText(temp.getItem()); 
     description.setText(temp.getDescription()); 

     return row; 
    } 

} 

class PlotOptionsListItem { 

    private String item; 
    private String description; 

    public PlotOptionsListItem(String item, String description) { 
     // TODO Auto-generated constructor stub 
     this.setItem(item); 
     this.setDescription(description); 
    } 

    public String getItem() { 
     return item; 
    } 

    public void setItem(String item) { 
     this.item = item; 
    } 

    public String getDescription() { 
     return description; 
    } 

    public void setDescription(String description) { 
     this.description = description; 
    } 
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/container" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:gravity="center" 
    android:orientation="vertical" > 

    <ImageView 
      android:contentDescription="@string/activity_main_cover_image_desc" 
      android:id="@+id/imageView1" 
      android:layout_weight="1" 
      android:layout_width="match_parent" 
      android:layout_height="match_parent"  
      android:layout_margin="@dimen/activity_horizontal_margin" 
      android:src="@drawable/ic_launcher" /> 

    <RelativeLayout android:id="@+id/activity_main_button_layout" 
     android:layout_weight="1" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:orientation="vertical"> 

     <Button 
      android:id="@+id/button_create_plot" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:layout_alignParentTop="true" 
      android:layout_marginLeft="@dimen/activity_horizontal_margin" 
      android:layout_marginRight="@dimen/activity_horizontal_margin" 
      android:layout_marginTop="@dimen/activity_horizontal_margin_half" 
      android:layout_marginBottom="@dimen/activity_horizontal_margin" 
      android:layout_centerHorizontal="true" 
      android:text="@string/button_create_plot" /> 

     <Button 
      android:id="@+id/button_view_gallery" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content"    
      android:layout_below="@+id/button_create_plot" 
      android:layout_marginLeft="@dimen/activity_horizontal_margin" 
      android:layout_marginRight="@dimen/activity_horizontal_margin" 
      android:text="@string/button_view_gallery" /> 

     <Button 
      android:id="@+id/button_help_faq" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content"    
      android:layout_below="@+id/button_view_gallery" 
      android:layout_marginLeft="@dimen/activity_horizontal_margin" 
      android:layout_marginRight="@dimen/activity_horizontal_margin" 
      android:text="@string/button_help_faq" /> 

     <Button 
      android:id="@+id/button_advanced_settings" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content"    
      android:layout_below="@+id/button_help_faq" 
      android:layout_marginLeft="@dimen/activity_horizontal_margin" 
      android:layout_marginRight="@dimen/activity_horizontal_margin" 
      android:text="@string/button_advanced_settings" /> 

    </RelativeLayout> 

</LinearLayout>

activity_create_plot.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" > 

    <fragment 
     android:id="@+id/fragment_plot_options_list" 
     android:name="com.example.probaddieweaponplotter.PlotOptionsListFragment" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:layout_alignParentTop="true" 
     android:layout_centerHorizontal="true" /> 

    <fragment 
     android:id="@+id/fragment_generate_plot_button" 
     android:name="com.example.probaddieweaponplotter.GeneratePlotButtonFragment" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:layout_centerHorizontal="true" 
     tools:layout="@layout/fragment_plot_options_detail" /> 

</RelativeLayout>

fragment_plot_options_list.xml

<?xml version="1.0" encoding="utf-8"?> 
<ListView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:id="@+id/plot_options_listView" 
    android:layout_height="match_parent" 
    android:orientation="vertical" >   
</ListView>

plot_options_list_single_item.xml

그리고 마지막으로, 내 AndroidManifest.xml을

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.example.probaddieweaponplotter" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk 
     android:minSdkVersion="11" 
     android:targetSdkVersion="19" /> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" > 
     <activity 
      android:name="com.example.probaddieweaponplotter.MainActivity" 
      android:label="@string/app_name" > 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
     <activity 
      android:name="com.example.probaddieweaponplotter.CreatePlotActivity" 
      android:label="@string/title_activity_create_plot" 
      android:parentActivityName="com.example.probaddieweaponplotter.MainActivity" > 
      <meta-data 
       android:name="android.support.PARENT_ACTIVITY" 
       android:value="com.example.probaddieweaponplotter.MainActivity" /> 
     </activity> 
    </application> 

</manifest>

출처

2014-04-02 Nick Broderick

왜 이것을 downvoted했는지 공유 하시겠습니까? 존재한다면 복제물을 가르쳐 주시겠습니까? –

이 시도 ..

이

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
     Bundle savedInstanceState) {   
    View v = inflater.inflate(R.layout.fragment_plot_options_list, 
      container, false); 
    listView = (ListView) v.findViewById(R.id.plot_options_listView);  
    return v; 


} 

@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onActivityCreated(savedInstanceState); 

    MyAdapter adapter = new MyAdapter(getActivity()); 
    listView.setAdapter(adapter);   
}

출처

2014-04-02 05:55:38 Hariharan

ListView이 조각 레이아웃에 속한다. 그래서 당신은 조각의 활동의 전망을 초기화 할 getActivity()을 사용 ListView

를 초기화 onActivityCreated에 getView()를 사용하고 당신이 원하는 없습니다.

변경이

listView = (ListView) getActivity().findViewById(R.id.plot_options_listView);

에

listView = (ListView) getView().findViewById(R.id.plot_options_listView);

출처

2014-04-02 05:55:52 Raghunandan

당신의 추론은 내게 들리지만, 어떤 이유로이 문제를 해결하지 못했습니다. –

가 @NickBroderick이 API 수준에서 공공보기의 getView() 추가'봐 @NickBroderick 그 – Raghunandan

에 대해 의심의 여지를 작동 11 조각의 레이아웃의 루트 뷰 (onCreateView (LayoutInflater에서, 뷰 그룹, 번들에 의해 반환 된 하나를 얻을)). 조각의 루트보기 또는 레이아웃이없는 경우 null입니다. ' – Raghunandan

그냥 당신이 이유를 알아야한다고 생각 :

당신이 당신의 listview이 R.layout.fragment_plot_options_list입니다 가지고있는 당신의 조각의 레이아웃.당신이 findViewById 필요

는 팽창 레이아웃 반환하기 전에 fragment_plot_options_list.xml에서입니다 : 전화

return inflater.inflate(R.layout.fragment_plot_options_list, 
       container, false);

을 onActivityCreated에

listView = (ListView) getActivity().findViewById(R.id.plot_options_listView);

, 그 호출하지 않고 활동에서 같은 전화와 같은 setContentView()으로 가면 NPE를 얻을 수 있습니다.

출처

2014-04-02 06:13:12 user2450263

설명해 주셔서 감사합니다. 불행히도, 이것은 내가 현재 줄 수없는 upvote 자격이 있습니다. –

문제가없는 사람, 환영합니다. 주셔서 감사합니다. – user2450263

새로운 액티비티를 시작할 때 NPE가 throw됩니다.

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