Android 当我在片段上编写代码时，为什么应用程序会崩溃？

我写了一些代码片段。当我这样写的时候，它工作得很好吗

public class Fragmentone  extends Fragment{

    ArrayList<String> name;
    boolean isPressed=false;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_one, container, false);
        name=new ArrayList<String>();
        name.add("First Station");
        name.add("Second Station");


        ListView listView = (ListView) view.findViewById(R.id.list_view);



        ArrayAdapter arrayAdapter =new ArrayAdapter(getActivity(),R.layout.row_layout,R.id.station_name,name);
        listView.setAdapter(arrayAdapter);



        return view;
    }


}

更新代码

问题是view.findviewbydr.id.favorite找不到具有该IDfavorite的图像视图。在layout R.layout.fragment_one中查找该图像ID，并确保其存在。

这是因为ImageButton是ListView行的一部分，而不是片段的视图层次结构的一部分。就你而言

ImageButton imageButton = (ImageButton) view.findViewById(R.id.favorite);

正在返回空引用。要处理行的单击，应该调用，传递实现AdapterView.OnItemClickListener的类的实例

例如

---

你的日志在哪里？？？post It Wait我将为您提供emove android:onClick=OnToggleStars，直到在这行imageButton.setBackgroundResourceR.drawable.off；上得到相同的错误；。我的imageButton对象为空。请详细说明我将如何在图像按钮上显示toat。请检查我更新的片段代码。我想在图像按钮上显示toast。单击将android:DegenantFocusability=BlocksDensedSendants添加到行中的线性布局xml:not Worring这是我的代码。请检查更新它是否正常工作使用此属性以及用户如何区分行单击和图像按钮单击..感谢您的帮助

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/station_name"
        android:padding="10dp"
        android:textColor="#eee345"
        android:textAppearance="?android:textAppearanceLarge"
        />

    <ImageButton android:id="@+id/favorite"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:src="@drawable/start"
        android:background="#00ffffff"
        android:onClick="onToggleStar"/>


</LinearLayout>

public class Fragmentone  extends Fragment{

    ArrayList<String> name;
    boolean isPressed=false;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_one, container, false);
        name=new ArrayList<String>();
        name.add("First Station");
        name.add("Second Station");


        ListView listView = (ListView) view.findViewById(R.id.list_view);
        ImageButton imageButton = (ImageButton) view.findViewById(R.id.favorite);
        imageButton.setBackgroundResource(R.drawable.off);

        imageButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(isPressed){
                    v.setBackgroundResource(R.drawable.off);
                }else{
                    v.setBackgroundResource(R.drawable.on);
                }
                isPressed = !isPressed; // reverse
            }
        });


        ArrayAdapter arrayAdapter =new ArrayAdapter(getActivity(),R.layout.row_layout,R.id.station_name,name);
        listView.setAdapter(arrayAdapter);



        return view;
    }


}

08-31 13:18:31.900  21769-21769/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.naveen.tabsfavourite, PID: 21769
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setBackgroundResource(int)' on a null object reference
            at com.example.naveen.tabsfavourite.Fragmentone.onCreateView(Fragmentone.java:34)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
            at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:490)
            at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:1105)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:951)
            at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1473)
            at android.view.View.measure(View.java:17547)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
            at android.view.View.measure(View.java:17547)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
            at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:447)
            at android.view.View.measure(View.java:17547)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2615)
            at android.view.View.measure(View.java:17547)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
            at android.view.Choreographer.doCallbacks(Choreographer.java:580)
            at android.view.Choreographer.doFrame(Choreographer.java:550)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

public class Fragmentone  extends Fragment{

    ArrayList<String> name;
    boolean isPressed=false;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_one, container, false);
        name=new ArrayList<String>();
        name.add("First Station");
        name.add("Second Station");


        ListView listView = (ListView) view.findViewById(R.id.list_view);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                String item = (String) parent.getItemAtPosition(position);
                Toast.makeText(getActivity(), "Item : " + item, Toast.LENGTH_SHORT).show();
            }
        });

        ArrayAdapter arrayAdapter =new ArrayAdapter(getActivity(),R.layout.row_layout,R.id.station_name,name);
        listView.setAdapter(arrayAdapter);



        return view;
    }


}



<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#325633"
    android:descendantFocusability="blocksDescendants">

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/list_view">
    </ListView>

</LinearLayout>

ImageButton imageButton = (ImageButton) view.findViewById(R.id.favorite);

listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
      @Override
      public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
          String item = parent.getItemAtPosition(position);
          Toast.makeText(getActivity(), "Item : " + item, Toast.LENGTH_SHORT).show();                
       }
});