自定義ListView適配器 - 空指針異常

Question

我gettin NullPointerException「lv.setAdapter（適配器）;」我不明白，我在適配器中更改了一些代碼，但隨後我刪除了它們。然後這個例外就開始了。

在kimdenlistduzeltilmis

：4值

在konulist

：4值

final LayoutInflater mLInflater = getLayoutInflater(); 
     final ListViewAdapter adapter = new ListViewAdapter(
       getApplicationContext(), kimdenlistduzeltilmis, konulist, 
       mLInflater); 
     lv.setAdapter(adapter); 
     lv.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> parent, View item, 
        int position, long id) { 
       // adapter.Refresh(); 
       onClickPosition = position; 
       try { 
        EkDurumu ekdurumuNesnesi = new EkDurumu(); 
        ekdurumuNesnesi.MessagePositionEkBulunuyormu(
          onClickPosition, goruntuleNesnesi.getMessages()); 

       } catch (Exception e) { 
        e.printStackTrace(); 
       } 

而且ListViewAdapter：

import java.util.ArrayList; 
import java.util.HashMap; 

import android.content.Context; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.CheckBox; 
import android.widget.CompoundButton; 
import android.widget.ImageView; 
import android.widget.TextView; 
import android.widget.CompoundButton.OnCheckedChangeListener; 

public class ListViewAdapter extends BaseAdapter { 
    static HashMap<Integer, Boolean> cartItems = new HashMap<Integer, Boolean>(); 
    Context mContext; 
    ArrayList<String> kimdenlist; // to load images 
    ArrayList<String> konulist; // for data 
// ArrayList<String> imagelist; 
    LayoutInflater mLayoutInflater; 

    public ListViewAdapter(Context context, ArrayList<String> kimdenlist, ArrayList<String> konulist, 
      LayoutInflater layoutInflater) { 
     mContext = context; 
     this.kimdenlist = kimdenlist; 
     this.konulist = konulist; 
     mLayoutInflater = layoutInflater; 
    } 

    @Override 
    public int getCount() 
    { 
     return konulist.size(); // images array length 
    } 

    @Override 
    public Object getItem(int arg0) { 

     return null; 
    } 

    @Override 
    public long getItemId(int arg0) { 

     return 0; 
    } 

    int count = 0; 

    // customized Listview 
    @Override 
    public View getView(int position, View arg1, ViewGroup arg2) { 

     View v; 
     final int pos = position; 
     v = mLayoutInflater.inflate(R.layout.listust, null); 

     TextView kimden = (TextView) v.findViewById(R.id.textvKimden); 
     kimden.setText(kimdenlist.get(position)); 
     TextView konu = (TextView) v.findViewById(R.id.textvKonu); 
     konu.setText(konulist.get(position)); 

//  // saving check box state at the time of raloading 
     CheckBox ch = (CheckBox) v.findViewById(R.id.chk); 
     try { 
      if (count != 0) { 
       boolean b = cartItems.get(pos); 
       if (b == false) 
        ch.setChecked(false); 
       else 
        ch.setChecked(true); 
      } 
     } catch (NullPointerException e) { 

     } 


     ch.setOnCheckedChangeListener(new OnCheckedChangeListener() { 
      @Override 
      public void onCheckedChanged(CompoundButton arg0, boolean arg1) { 
       cartItems.put(pos, arg1); 
       count++; 

      } 
     }); 
     return v; 
    } 

    public static HashMap<Integer, Boolean> getcartItems() { 
     return cartItems; 
    } 

    public void Remove() 
     { 
     notifyDataSetChanged(); 
     } 

} 

而我的logcat：

05-16 16:13:12.962: E/AndroidRuntime(347): FATAL EXCEPTION: main 
05-16 16:13:12.962: E/AndroidRuntime(347): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mobil.eposta/com.mobil.eposta.ListeleActivity}: java.lang.NullPointerException 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.os.Handler.dispatchMessage(Handler.java:99) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.os.Looper.loop(Looper.java:123) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.app.ActivityThread.main(ActivityThread.java:4627) 
05-16 16:13:12.962: E/AndroidRuntime(347): at java.lang.reflect.Method.invokeNative(Native Method) 
05-16 16:13:12.962: E/AndroidRuntime(347): at java.lang.reflect.Method.invoke(Method.java:521) 
05-16 16:13:12.962: E/AndroidRuntime(347): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
05-16 16:13:12.962: E/AndroidRuntime(347): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
05-16 16:13:12.962: E/AndroidRuntime(347): at dalvik.system.NativeStart.main(Native Method) 
05-16 16:13:12.962: E/AndroidRuntime(347): Caused by: java.lang.NullPointerException 
05-16 16:13:12.962: E/AndroidRuntime(347): at com.mobil.eposta.ListeleActivity.onCreate(ListeleActivity.java:109) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
05-16 16:13:12.962: E/AndroidRuntime(347): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
05-16 16:13:12.962: E/AndroidRuntime(347): ... 11 more 

Answer 1

看起來你的ListView爲空。嘗試添加

lv = (ListView) findViewById(R.id.whatever_id_you_gave_your_listview); 

調用setAdapter（）之前