自定义列表视图 Android 的 getView nullPointerException

Question

我有 2 个自定义列表视图，用于显示不同的类别。但是，当创建第二个列表视图时，从getView 返回时，我得到了这个NullPointerException。我无法弄清楚其中的原因。

代码如下：

CustomListAdapter：

public class CustomListAdapter extends ArrayAdapter<String>{

    Context context;
    String[] stringList;
    TextView medium, small;


    public CustomListAdapter (Context con, String[] sL)
    {
        super(con, R.layout.my_list, R.id.mediumTextInList, sL); 
        context = con;

        stringList = sL;


    }

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



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

        View newRowView = inflator.inflate(R.layout.my_list, parent,false); 


        medium = (TextView) newRowView.findViewById(R.id.mediumTextInList);
        small = (TextView) newRowView.findViewById(R.id.smallText);

        medium.setText(stringList[position]);

        return super.getView(position, newRowView, parent);
    }

}

列表活动：

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);

        Bundle myBasket = new Bundle();

        myBasket.putString("name", categoryName);

        Intent myIntent = new Intent(myFirstList.this, mySecondList.class);

        myIntent.putExtras(myBasket);
        startActivity(intent); 
 }

堆栈跟踪：

07-28 17:04:46.551: E/AndroidRuntime(2290): FATAL EXCEPTION: main 
07-28 17:04:46.551: E/AndroidRuntime(2290): java.lang.NullPointerException
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:355)  
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:323)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at com.umer.androiduetproject.CustomListAdapterForDeptAndSemesters.getView(CustomListAdapterForDeptAndSemesters.java:53)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.AbsListView.obtainView(AbsListView.java:1430)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.ListView.makeAndAddView(ListView.java:1745)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.ListView.fillDown(ListView.java:670)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.ListView.fillFromTop(ListView.java:727)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.ListView.layoutChildren(ListView.java:1584)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.AbsListView.onLayout(AbsListView.java:1260)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.view.View.layout(View.java:7175)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.view.View.layout(View.java:7175)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.view.View.layout(View.java:7175)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1140)
07-28 17:04:46.551: E/AndroidRuntime(2290):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)

问候

Answer 1

你不应该调用 super.getView，只需要返回 newRowView。

Answer 2

你可以这样用。

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

    ViewHolder holder;
    View newRowView = convertView;

    if (convertView == null) {
        LayoutInflater inflator = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

        newRowView = inflator.inflate(R.layout.my_list, parent,false);
        holder = new ViewHolder();
        holder.medium = (TextView) newRowView.findViewById(R.id.mediumTextInList);
        holder.small = (TextView) newRowView.findViewById(R.id.smallText);

        newRowView .setTag(holder);
       }

     else {

          holder = (ViewHolder) newRowView .getTag();
          }

         holder.medium.setText(stringList[position]);

        return newRowView ;
    }

Answer 3

stringList 中有空值吗？方法toString()可以在super.getView()中调用。