NullPointerException in custom adapter getView

问题:

I'm coding a custom adapter for a ListView that has a custom list to it.

obviously, I have to write the getView function. so here is my code:

/*1*/ public View getView(int position, View convertView, ViewGroup parent) { /*2*/    View vi = convertView; /*3*/    if (convertView == null) /*4*/        vi = inflater.inflate(R.layout.result_list_item, null); /*5*/ /*6*/    TextView title = (TextView) vi.findViewById(R.id.tvTitle); /*7*/    TextView subtitle = (TextView) vi.findViewById(R.id.tvSubTitle); /*8*/    ImageView image = (ImageView) vi.findViewById(R.id.imageView1); /*9*/ /*10*/   title.setText(data.get(position).getDescription().toString()); /*11*/   subtitle.setText(data.get(position).getDate().toString()); /*12*/   String img = "http://someLink/" + data.get(position).getId() + "a_t.jpg"; /*13*/   imageLoader.DisplayImage(img, image); /*14*/   return vi; /*15*/ } 

But, I have noticed that on line number 6 the program crashes with a NullPointer exception.

here is my crash report:

04-18 09:33:32.745: E/AndroidRuntime(2209): FATAL EXCEPTION: main 04-18 09:33:32.745: E/AndroidRuntime(2209): java.lang.NullPointerException 04-18 09:33:32.745: E/AndroidRuntime(2209):     at com.package.mojo.NoPicAdapter.getView(NoPicAdapter.java:46) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.AbsListView.obtainView(AbsListView.java:1554) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1264) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.ListView.onMeasure(ListView.java:1175) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.View.measure(View.java:8366) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:386) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.View.measure(View.java:8366) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.View.measure(View.java:8366) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:531) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.View.measure(View.java:8366) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.View.measure(View.java:8366) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.ViewRoot.performTraversals(ViewRoot.java:847) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1868) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.os.Handler.dispatchMessage(Handler.java:99) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.os.Looper.loop(Looper.java:123) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at android.app.ActivityThread.main(ActivityThread.java:3691) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at java.lang.reflect.Method.invokeNative(Native Method) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at java.lang.reflect.Method.invoke(Method.java:507) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605) 04-18 09:33:32.745: E/AndroidRuntime(2209):     at dalvik.system.NativeStart.main(Native Method) 

of course, the layout and the items themselves exist...

any thoughts?

update: when i look at the variables while debugging, I see that vi was not inflated (vi == null), why?

回答1:

Change this:

vi = inflater.inflate(R.layout.result_list_item, null); 

To this:

vi = inflater.inflate(R.layout.result_list_item, parent, false); 

---

this is how your adapter should be:

public class NoPicAdapter extends ArrayAdapter {      private ArrayList data;     private Activity mActivity;     private LayoutInflater inflater = null;      public NoPicAdapter(Activity a, ArrayList d) {         super(a, R.layout.no_pic_list_item, d);         mActivity = a;         data = d;         inflater = (LayoutInflater) mActivity                 .getSystemService(Context.LAYOUT_INFLATER_SERVICE);     }       @Override     public View getView(int position, View convertView, ViewGroup parent) {         View vi = convertView;         if (vi == null)             vi = inflater.inflate(R.layout.no_pic_list_item, parent, false);         TextView title = (TextView) vi.findViewById(R.id.noPicTitle);         TextView subtitle = (TextView) vi.findViewById(R.id.noPicSubtitle);          title.setText(data.get(position).getmTitle());         subtitle.setText(data.get(position).getmPubDate());          return vi;     }  } 

回答2:

Try this

vi = LayoutInflater.from(mActivity).inflate(R.layout.result_list_item, null);

if mActivity is your Activity context passed from the activity where you are creating the object of this adapter.

回答3:

are you initializing inflater? if not initialize it.

inflater = getLayoutInflater(); 

or

 inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

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