实施CustomAdapter到碎片的ListView

Question

我是学尝试落实片段和ListView CustomAdapter，但它显示androidListView.setAdapter(androidListAdapter);

错误NullPointerException异常以前我试过CustomAdapter没有碎片，这是一个成功的

这是我的片段代码：

public class LaporanFragment extends Fragment { 
private ArrayAdapter<String> mLaporanAdapter; 
String androidListViewStrings[] = {"Android ListView Example", "Android Custom ListView Example", "Custom ListView Example", 
     "Android List Adapter", "Custom Adapter ListView", "ListView Tutorial", 
     "ListView with Image and Text", "Custom ListView Text and Image", "ListView Custom Tutorial"}; 

Integer image_id[] = {R.mipmap.ic_launcher, R.mipmap.ic_launcher, R.mipmap.ic_launcher, 
     R.mipmap.ic_launcher, R.mipmap.ic_launcher, R.mipmap.ic_launcher, 
     R.mipmap.ic_launcher, R.mipmap.ic_launcher, R.mipmap.ic_launcher}; 

public LaporanFragment(){ 
} 

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

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.fragment_laporan, container, false); 
    LaporanAdapter androidListAdapter = new LaporanAdapter(getActivity(), image_id, androidListViewStrings); 
    ListView androidListView = (ListView) rootView.findViewById(R.id.list_view_laporan); 
    androidListView.setAdapter(androidListAdapter); **//Error nullPointerExeption on this line** 

    return rootView; 
}} 

这是我的自定义适配器代码：

public class LaporanAdapter extends ArrayAdapter { 
String[] androidListViewStrings; 
Integer[] imagesId; 
Context context; 

public LaporanAdapter(Activity context, Integer[] imagesId, String[] textListView) { 
    super(context, R.layout.list_item_laporan, textListView); 
    this.androidListViewStrings = textListView; 
    this.imagesId = imagesId; 
    this.context = context; 
} 

@Override 
public View getView(int i, View view, ViewGroup viewGroup) { 
    LayoutInflater layoutInflater = (LayoutInflater) context 
      .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    View viewRow = layoutInflater.inflate(R.layout.list_item_laporan, null, 
      true); 
    TextView mtextView = (TextView) viewRow.findViewById(R.id.list_item_laporan_textview); 
    ImageView mimageView = (ImageView) viewRow.findViewById(R.id.image_view); 
    mtextView.setText(androidListViewStrings[i]); 
    mimageView.setImageResource(imagesId[i]); 
    return viewRow; 
}} 

UPDATE：

logcat的输出：

FATAL EXCEPTION: main 
      Process: id.co.gloftech.pelaporandishub, PID: 4859 
      java.lang.RuntimeException: Unable to start activity ComponentInfo{id.co.gloftech.pelaporandishub/id.co.gloftech.pelaporandishub.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference 
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325) 
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
       at android.app.ActivityThread.access$800(ActivityThread.java:151) 
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
       at android.os.Handler.dispatchMessage(Handler.java:102) 
       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) 
      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference 
       at id.co.gloftech.pelaporandishub.LaporanFragment.onCreateView(LaporanFragment.java:85) 
       at android.support.v4.app.Fragment.performCreateView(Fragment.java:2087) 
       at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1113) 
       at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1295) 
       at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801) 
       at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1682) 
       at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388) 
       at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:607) 
       at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:181) 
       at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1236) 
       at android.app.Activity.performStart(Activity.java:6006) 
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2288) 
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)  
       at android.app.ActivityThread.access$800(ActivityThread.java:151)  
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)  
       at android.os.Handler.dispatchMessage(Handler.java:102)  
       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) 

而且fragment_laporan.xml

<FrameLayout 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" android:paddingLeft="@dimen/activity_horizontal_margin" 
android:paddingRight="@dimen/activity_horizontal_margin" 
android:paddingTop="@dimen/activity_vertical_margin" 
android:paddingBottom="@dimen/activity_vertical_margin" 
tools:context=".MainActivity$LaporanFragment"> 

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

Answer 1

你找错人ListView ID。所以rootView.findViewById(R.id.list_view_laporan)将返回null并导致NPE。

变化，

ListView androidListView = (ListView) rootView.findViewById(R.id.list_view_laporan); 

到，

ListView androidListView = (ListView) rootView.findViewById(R.id.list_view_forecast);