ListView適配器：無法啓動活動ComponentInfo {..}：java.lang.NullPointerException

Question

我試圖開始一個新的活動，並且我得到一個NullPointerException。 我不太確定我從哪裏得到NullPointerException。在調試期間，應用程序在創建適配器時崩潰，但我看不到在代碼中獲得NullPointerException的錯誤。

錯誤日誌：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.app/com.app.APP.SpaActivity}: java.lang.NullPointerException 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2394) 
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2446) 
     at android.app.ActivityThread.access$600(ActivityThread.java:165) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373) 
     at android.os.Handler.dispatchMessage(Handler.java:107) 
     at android.os.Looper.loop(Looper.java:194) 
     at android.app.ActivityThread.main(ActivityThread.java:5434) 
     at java.lang.reflect.Method.invokeNative(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:525) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:834) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
     at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.NullPointerException 
     at com.app.adapter.SpaListAdapter.<init>(SpaListAdapter.java:25) 
     at com.app.APP.SpaActivity.onCreate(SpaActivity.java:43) 
     at android.app.Activity.performCreate(Activity.java:5122) 
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1146) 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2358) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2446) 
        at android.app.ActivityThread.access$600(ActivityThread.java:165) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:194) 
        at android.app.ActivityThread.main(ActivityThread.java:5434) 
        at java.lang.reflect.Method.invokeNative(Native Method) 
        at java.lang.reflect.Method.invoke(Method.java:525) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:834) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
        at dalvik.system.NativeStart.main(Native Method) 

SpaActivity.java

public class SpaActivity extends Activity { 

    private ProgressDialog pDialog; 
    private List<Spa> SpaList = new ArrayList<Spa>(); 
    private ListView listView; 
    private SpaListAdapter adapter; 

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

     listView = (ListView) findViewById(R.id.list); 
     adapter = new SpaListAdapter(this, SpaList); 

     listView.setAdapter(adapter); 

activity_spa.xml

<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"> 

    <ListView 
     android:id="@+id/list" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:divider="@color/list_divider" 
     android:dividerHeight="1dp" 
     android:listSelector="@layout/list_row_selector" /> 

</RelativeLayout> 

爲ListView適配器：

public class SpaListAdapter extends BaseAdapter { 
    private Activity activity; 
    private LayoutInflater inflater; 
    private List<Spa> SpaItems; 
    ImageLoader imageLoader = AppController.getInstance().getImageLoader(); 

    public SpaListAdapter(Activity activity, List<Spa> SpaItems) { 
     this.activity = activity; 
     this.SpaItems = SpaItems; 
    } 

    @Override 
    public int getCount() { 
     return SpaItems.size(); 
    } 

    @Override 
    public Object getItem(int location) { 
     return SpaItems.get(location); 
    } 

    @Override 
    public long getItemId(int position) { 
     return position; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     if (inflater == null) 
      inflater = (LayoutInflater) activity 
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
     if (convertView == null) 
      convertView = inflater.inflate(R.layout.list_row, null); 

     if (imageLoader == null) 
      imageLoader = AppController.getInstance().getImageLoader(); 
     NetworkImageView thumbNail = (NetworkImageView) convertView 
       .findViewById(R.id.thumbnail); 
     TextView title = (TextView) convertView.findViewById(R.id.title); 
     TextView duration = (TextView) convertView.findViewById(R.id.duration); 
     TextView description = (TextView) convertView.findViewById(R.id.description); 
     TextView price = (TextView) convertView.findViewById(R.id.price); 

     // getting spa data for the row 
     Spa s = SpaItems.get(position); 

     // thumbnail image 
     thumbNail.setImageUrl(s.getThumbnailUrl(), imageLoader); 

     // title 
     title.setText(s.getTitle()); 

     // duration 
     duration.setText("Time: " + String.valueOf(s.getDuration())); 

     // description 
     description.setText(String.valueOf(s.getDescription())); 

     // price 
     price.setText("Price: " + String.valueOf(s.getPrice())); 

     return convertView; 
    } 

} 

最後的適配器

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:background="@layout/list_row_selector" 
    android:padding="8dp" > 

    <!-- Thumbnail Image --> 
    <com.android.volley.toolbox.NetworkImageView 
     android:id="@+id/thumbnail" 
     android:layout_width="80dp" 
     android:layout_height="80dp" 
     android:layout_alignParentLeft="true" 
     android:layout_marginRight="8dp" /> 

    <!-- Spa Title --> 
    <TextView 
     android:id="@+id/title" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignTop="@+id/thumbnail" 
     android:layout_toRightOf="@+id/thumbnail" 
     android:textSize="@dimen/title" 
     android:textStyle="bold" /> 

    <!-- Duration --> 
    <TextView 
     android:id="@+id/duration" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:layout_below="@id/title" 
     android:layout_marginTop="1dip" 
     android:layout_toRightOf="@+id/thumbnail" 
     android:textSize="@dimen/rating" /> 

    <!-- Description --> 
    <TextView 
     android:id="@+id/description" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:layout_below="@id/duration" 
     android:layout_marginTop="5dp" 
     android:layout_toRightOf="@+id/thumbnail" 
     android:textColor="@color/genre" 
     android:textSize="@dimen/genre" /> 

    <!-- Price --> 
    <TextView 
     android:id="@+id/price" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:layout_alignParentRight="true" 
     android:textColor="@color/year" 
     android:textSize="@dimen/year" /> 

</RelativeLayout> 

Answer 1

錯誤的list_row.xml是在你spalistadatper班線25。 您的方法getItemId（）需要修改。

@Override 
    public long getItemId(int position) { 
     return SpaItems.indexOf(getItem(position)); 
    }