android - 自定义适配器 onclicklistener 按钮 NPE *android

Question

我在我的 ListView 中获取 NPE..所以当我点击按钮时，它会显示我在另一个表单上设置的数据..

这是我的自定义适配器代码:

public class AdapterListPemesananMenu extends BaseAdapter {
    public static ArrayList<MenuInputClass> searchArrayList;

    private LayoutInflater mInflater;

    public AdapterListPemesananMenu(Context context, ArrayList<MenuInputClass> results) {
        searchArrayList = results;
        mInflater = LayoutInflater.from(context);
    }   


    public AdapterListPemesananMenu(OnClickListener onClickListener,
            ArrayList<MenuInputClass> searchResults) {
        // TODO Auto-generated constructor stub
    } 


    public int getCount() {
        return searchArrayList.size(); *********************the NPE is here
    }

    public Object getItem(int position) {
        return searchArrayList.get(position);
    }

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

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.list_pemesananmenu_row, null);
            holder = new ViewHolder();
            holder.txtName = (TextView) convertView.findViewById(R.id.txtNamaMasuk);
            holder.txtCityState = (TextView) convertView
                    .findViewById(R.id.txtJumlahMasuk);


            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.txtName.setText(searchArrayList.get(position).getNama_menu());
        holder.txtCityState.setText(searchArrayList.get(position)
                .getJumlah_menu());


        return convertView;
    }

    static class ViewHolder {
        TextView txtName;
        TextView txtCityState;

    }
}

这是我的 Activity 代码:

public class SingleListView_Activity extends Activity{

    Button order;       
    public static ListView list_pemesanan;    
    public static String nama_menu;
    TextView namamenu;
    public static String jumlah_menu;
    EditText jumlahmenu;  
    //public static ArrayList<MenuInputClass> searchResults = GetSearchResults();

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.single_list_view);  

        ListView list_single_list_view=(ListView)findViewById(R.id.list_single);    
        list_pemesanan = (ListView)findViewById(R.id.list);
        namamenu=(TextView)findViewById(R.id.nama_menu2);
        jumlahmenu = (EditText)findViewById(R.id.txtJumlahOrder);

        order=(Button)findViewById(R.id.btn_order);
        //when this button on click its set the data to my another form
        order.setOnClickListener(new OnClickListener() { 
                @Override
                public void onClick(View v) {                                             

                     ArrayList<MenuInputClass> searchResults = GetSearchResults();              
                      ListPemesanan_Activity.list_pemesanan.setAdapter(new AdapterListPemesananMenu(this,searchResults));   

                }

             });


    }

     private ArrayList<MenuInputClass> GetSearchResults(){
     //this is the data that i set
         ArrayList<MenuInputClass> results = new ArrayList<MenuInputClass>();

         MenuInputClass sr = new MenuInputClass();      
         sr.setJumlah_menu("asdas");
         sr.setNama_menu("2");
         results.add(sr);                
         return results;
        }
}

日志:

10-23 04:33:19.759: E/AndroidRuntime(14459): FATAL EXCEPTION: main
10-23 04:33:19.759: E/AndroidRuntime(14459): java.lang.NullPointerException
10-23 04:33:19.759: E/AndroidRuntime(14459):    at list_pemesananmenu_view.AdapterListPemesananMenu.getCount(AdapterListPemesananMenu.java:35)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.widget.ListView.setAdapter(ListView.java:479)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at list_pemesananmenu_view.SingleListView_Activity$1.onClick(SingleListView_Activity.java:123)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.view.View.performClick(View.java:2538)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.view.View$PerformClick.run(View.java:9152)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.os.Handler.handleCallback(Handler.java:587)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.os.Handler.dispatchMessage(Handler.java:92)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.os.Looper.loop(Looper.java:130)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.app.ActivityThread.main(ActivityThread.java:3693)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at java.lang.reflect.Method.invokeNative(Native Method)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at java.lang.reflect.Method.invoke(Method.java:507)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:665)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at dalvik.system.NativeStart.main(Native Method)
10-23 04:33:19.769: E/(195): Dumpstate > /data/log/dumpstate_app_error
10-23 04:33:20.059: E/AudioPolicyManager(129): stopOutput stream = 1 , mHardwareOutput = 1, output = 1 

任何帮助将不胜感激...谢谢!!

Answer 1

order.setOnClickListener(new OnClickListener() { 
   @Override
   public void onClick(View v) {                                             
      ArrayList<MenuInputClass> searchResults = GetSearchResults();              
      ListPemesanan_Activity.list_pemesanan.setAdapter(new AdapterListPemesananMenu(this,searchResults));   
   }
});

在上面的代码中，你调用了 new AdapterListPemesananMenu(OnClickListener onClickListener, ArrayList searchResults);

“this”指的是 OnClickListener，而不是本例中的 Activity ，因为您在新的 OnClickListener() block 中。

该构造函数不会初始化您的 searchArrayList。 searchArrayList 仅在采用 (Context, ArrayList) 的构造函数中初始化。

如果你想让其余的代码保持不变，你或许可以这样做

ListPemesanan_Activity.list_pemesanan.setAdapter(new AdapterListPemesananMenu(getApplicationContext(), searchResults));   

并且还去掉了将 OnClickListener 作为参数的 AdapterListPemesananMenu 构造函数以避免混淆。

这是 NPE 的快速修复/分析，可能有更好的方法来重新安排您的代码以实现您想要实现的目标。