堆棧內存溢出
  簡體   English   中英

方向更改期間NullPointerException

[英]NullPointerException during orientation change

 原文  2013-11-02 14:10:39  6   1    android/ nullpointerexception/ orientation/ fragment

問題描述

我想為不同的orietation模式構建具有不同布局的應用程序。 所以我建立我的項目同樣做了它的android教程[這里的例子] 。 但是有一點不同，當我想要各種方向模式（風景，肖像等）時，本教程創建了不同大小（正常和大）。 現在我在方向更改期間收到NullPointerException 。 這是我的代碼：

HeadlinesFragment： 

public class HeadlinesFragment extends ListFragment {

   OnHeadlineSelectedListener HeadlinesCallback;
   List<Person> personLista = new ArrayList<Person>();

   public interface OnHeadlineSelectedListener {
        public void onArticleSelected(Person person);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ?
                android.R.layout.simple_list_item_activated_1 : android.R.layout.simple_list_item_1;

        //TESTOWE WYPENIENIE
        for(int i=0; i<10; i++){
            personLista.add(new Person("Imie"+i+"Nazwisko"+i,"email"+i+"@example"+i+".com"));
        }
        String[] niceTime = new String[personLista.size()];
        for(int i=0; i<personLista.size(); i++){
            niceTime[i] = personLista.get(i).getName();
        }
        //KONIEC

        setListAdapter(new ArrayAdapter<String>(getActivity(), layout, niceTime));
    }
    @Override
    public void onStart() {
        super.onStart();

        // When in two-pane layout, set the listview to highlight the selected list item
        // (We do this during onStart because at the point the listview is available.)
        if (getFragmentManager().findFragmentById(R.id.person_view) != null) {
            getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        }
    }

    @Override
    public void onAttach(Activity activity){
        super.onAttach(activity);

        try{
            HeadlinesCallback = (OnHeadlineSelectedListener)activity;
        }catch(ClassCastException e){
            throw new ClassCastException(activity.toString()
                    + " have to implement OnHeadlineSelectedListener");
        }
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id){
        HeadlinesCallback.onArticleSelected(personLista.get(position));

        getListView().setItemChecked(position, true);
    }

}

PersonFragment： 

public class PersonFragment extends Fragment{
   public static Person person;
   ImageView icon;
   TextView text1;
   TextView text2;
   TextView text3;

    View view;
   @Override
   public View onCreateView(LayoutInflater inflater, ViewGroup container, 
        Bundle savedInstanceState) {

       if(savedInstanceState != null){
           person = (Person)savedInstanceState.getSerializable("person");
       }

       view = inflater.inflate(R.layout.person_view, container, false);

       icon = (ImageView)view.findViewById(R.id.icon);
       text1 = (TextView)view.findViewById(R.id.name);
       text2 = (TextView)view.findViewById(R.id.email);
       text3 = (TextView)view.findViewById(R.id.info);

       return view;
    }
    @Override
    public void onStart() {
        super.onStart();

        Bundle args = getArguments();
        if (args != null) {
            person = (Person)args.getSerializable("context");

            text1.setText(person.getName());
            text2.setText(person.getEmail());
            text3.setText("Quisque semper ultricies iaculis. Vestibulum nec metus adipiscing, egestas sem mattis, ornare nulla. Quisque nec nibh nec lacus euismod gravida. Proin at pretium enim. In auctor, nisi sit amet pharetra facilisis, est justo mattis mi, eget mattis tortor ligula non orci. Vestibulum neque augue, elementum vitae aliquam non, condimentum ac dui. Nullam ultricies velit nec diam aliquam, sed lacinia sem eleifend. Quisque quam sapien, sodales id suscipit nec, consequat vel nunc. Quisque eu velit nisi. Donec varius consequat metus, tempor semper tortor ultricies vel. Mauris eget arcu nisi. Proin sit amet dui nisl. Quisque auctor lobortis augue sit amet egestas. Fusce mattis aliquam ante, et bibendum nibh ullamcorper et. Integer ipsum nibh, placerat a felis ut, accumsan rutrum eros. Quisque lacinia facilisis ipsum sed commodo.");
            icon.setImageResource(R.drawable.ic_launcher);

        }else{
            if(person==null){
                person = new Person("Test Testowy", "Testowy@gmail.com");
            }
            updateArticleView(person);
        }
    }
    @Override
    public void onSaveInstanceState(Bundle outState){
        super.onSaveInstanceState(outState);
        outState.putSerializable("person", person);
    }
    public void updateArticleView(Person externalPerson) {
        this.person = externalPerson;

        text1.setText(externalPerson.getName());
        text2.setText(externalPerson.getEmail());
        text3.setText("Quisque semper ultricies iaculis. Vestibulum nec metus adipiscing, egestas sem mattis, ornare nulla. Quisque nec nibh nec lacus euismod gravida. Proin at pretium enim. In auctor, nisi sit amet pharetra facilisis, est justo mattis mi, eget mattis tortor ligula non orci. Vestibulum neque augue, elementum vitae aliquam non, condimentum ac dui. Nullam ultricies velit nec diam aliquam, sed lacinia sem eleifend. Quisque quam sapien, sodales id suscipit nec, consequat vel nunc. Quisque eu velit nisi. Donec varius consequat metus, tempor semper tortor ultricies vel. Mauris eget arcu nisi. Proin sit amet dui nisl. Quisque auctor lobortis augue sit amet egestas. Fusce mattis aliquam ante, et bibendum nibh ullamcorper et. Integer ipsum nibh, placerat a felis ut, accumsan rutrum eros. Quisque lacinia facilisis ipsum sed commodo.");
        icon.setImageResource(R.drawable.ic_launcher);

    }

}

和MainActivity： 

public class MainActivity extends FragmentActivity implements OnHeadlineSelectedListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if(findViewById(R.id.fragment_container)!=null){

        if (savedInstanceState != null) {
            return;
        }

        getSupportFragmentManager().beginTransaction()
            .add(R.id.fragment_container, new HeadlinesFragment()).commit();

    }


}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
@Override
public void onArticleSelected(Person person) {

    PersonFragment fragment = (PersonFragment)getSupportFragmentManager().findFragmentById(R.id.person_view);

    if(fragment!=null){
        fragment.updateArticleView(person);
    }else{
        PersonFragment newFragment = new PersonFragment();

        Bundle args = new Bundle();
        args.putSerializable("context", person);
        newFragment.setArguments(args);

        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.fragment_container, newFragment);
        transaction.addToBackStack(null);

        transaction.commit();
    }
}

}

問題：在開始時一切都還可以，但是當我將方向模式更改為橫向（在模擬器ctrl + f12中）並再次返回到portain並從listview中選擇一些東西時我得到“遺憾的是應用程序停止了”。

它是logcat： 

11-02 14:29:03.396: E/AndroidRuntime(802): FATAL EXCEPTION: main
11-02 14:29:03.396: E/AndroidRuntime(802): java.lang.NullPointerException
11-02 14:29:03.396: E/AndroidRuntime(802):  at com.example.friendslist.PersonFragment.updateArticleView(PersonFragment.java:68)
11-02 14:29:03.396: E/AndroidRuntime(802):  at com.example.friendslist.MainActivity.onArticleSelected(MainActivity.java:43)
11-02 14:29:03.396: E/AndroidRuntime(802):  at com.example.friendslist.HeadlinesFragment.onListItemClick(HeadlinesFragment.java:69)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.support.v4.app.ListFragment$2.onItemClick(ListFragment.java:58)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.widget.AdapterView.performItemClick(AdapterView.java:298)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:2749)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.widget.AbsListView$1.run(AbsListView.java:3423)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.os.Handler.handleCallback(Handler.java:725)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.os.Handler.dispatchMessage(Handler.java:92)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.os.Looper.loop(Looper.java:137)
11-02 14:29:03.396: E/AndroidRuntime(802):  at android.app.ActivityThread.main(ActivityThread.java:5041)
11-02 14:29:03.396: E/AndroidRuntime(802):  at java.lang.reflect.Method.invokeNative(Native Method)
11-02 14:29:03.396: E/AndroidRuntime(802):  at java.lang.reflect.Method.invoke(Method.java:511)
11-02 14:29:03.396: E/AndroidRuntime(802):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
11-02 14:29:03.396: E/AndroidRuntime(802):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
11-02 14:29:03.396: E/AndroidRuntime(802):  at dalvik.system.NativeStart.main(Native Method)

我的主要問題是我一直在尋找像“由...引起”的東西，在這里我沒有。 有人能告訴我哪里有問題嗎？

PS在正常的android例子中，當我將子文件夾的名稱從layout-large更改為layout-land時我有同樣的問題。

活動： 

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />

person_view： 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:layout_marginRight="10dp"
android:layout_marginLeft="10dp" >

<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" 
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/icon"
        android:layout_width="72dp"
        android:layout_height="74dp"
        android:src="@drawable/ic_launcher" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent" >

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/name"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Imie i nazwisko" />
            <TextView
                android:id="@+id/email"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="email@sample.com" />

        </LinearLayout>

    </LinearLayout>

</LinearLayout>

<TextView
    android:id="@+id/info"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:text="info" />

土地子文件夾中的主要活動： 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">

<fragment android:name="com.example.friendslist.HeadlinesFragment"
          android:id="@+id/headlines_fragment"
          android:layout_weight="1"
          android:layout_width="0dp"
          android:layout_height="match_parent" />

<fragment android:name="com.example.friendslist.PersonFragment"
          android:id="@+id/person_view"
          android:layout_weight="2"
          android:layout_width="0dp"
          android:layout_height="match_parent" />

1 個解決方案

解決方案1
 1  2013-11-02 19:03:29

好吧，經過與這個問題的斗爭后，我找到了解決方案，我將onArticleSelected方法中的條件從(fragment!=null)更改為findViewById(R.id.fragment_container) 。 我不知道為什么，在定位改變片段仍然存在之后，也許有人可以解釋我。

編輯：//如果有人想要cheeck orientation setings，再次肯定一些元素等於null，你可以做得更簡單，例如： getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE

暫無
暫無

聲明:本站的技術帖子網頁，遵循CC BY-SA 4.0協議，如果您需要轉載，請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.

相關問題 方向更改后NullPointerException 方向更改時發生NullPointerException 屏幕方向更改時Android NullPointerException Android片段更改方向和NullPointerException 在方向更改期間創建片段 在方向更改期間保留參考 GLSurfaceView 在設備旋轉/方向更改時崩潰 - NullPointerException Android ViewPager在方向更改時始終崩潰，並出現NullPointerException 更改方向時更改照片尺寸 在方向更改期間管理滾動視圖中的滾動位置
相關標簽
 
粵ICP備18138465號  © 2020-2024 STACKOOM.COM