在列表视图中加载数据

我想通过中间类将数据加载到列表视图，我通过构造函数传输数据。但在数据加载过程中遇到了一个我无法解决的错误，希望人们帮助我。在列表视图中加载数据

类loadListview

public class LoadListView { 
private Context mContext = null; 
ArrayList<String> phonenumberArray = new ArrayList<String>(); 
ArrayList<String> codeInvoiceArray = new ArrayList<String>(); 
ArrayList<String> nameArray = new ArrayList<String>(); 
ArrayList<String> addressArray = new ArrayList<String>(); 
ArrayList<String> urlArray = new ArrayList<String>(); 
ListView listview=(ListView)((Activity)mContext).findViewById(R.id.listView1); 
String name,phonenumber,address,url,code,iddelivery; 

public LoadListView(Context mContext, String name,String phone,String address,String url,String code, String ID) 
{ 
    this.mContext=mContext; 
    this.name=name; 
    this.phonenumber=phone; 
    this.code=code; 
    this.address=address; 
    this.url=url; 
    this.iddelivery=ID; 
} 


// Xóa các item trong mảng để tránh sự trùng lặp 
public void clearArray() 
{ 
    codeInvoiceArray.clear(); 
    nameArray.clear(); 
    phonenumberArray.clear(); 
    addressArray.clear(); 
    urlArray.clear(); 
} 

// load dữ liệu lên listview 
public void loaddatalistview() 
{ 
    clearArray(); 
    phonenumberArray.add(phonenumber); 
    codeInvoiceArray.add(code); 
    nameArray.add(name); 
    addressArray.add(address); 
    urlArray.add(url); 
    listview.setAdapter(new DataAdapter(mContext, codeInvoiceArray 
      .toArray(new String[codeInvoiceArray.size()]), nameArray 
      .toArray(new String[nameArray.size()]), phonenumberArray 
      .toArray(new String[phonenumberArray.size()]), addressArray 
      .toArray(new String[addressArray.size()]))); 
    listview.setOnItemClickListener(new OnItemClickListener() { 

     // xử lý sự kiện khi chọn item trên listview 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, 
       int position, long id) { 
      Intent j = new Intent(mContext, Menu_Main.class); 

      // lấy thông tin thông qua vị trí của item được chọn 
      String url = urlArray.get(position); 
      String address = addressArray.get(position); 
      String mahoadon = codeInvoiceArray.get(position); 
      String phone = phonenumberArray.get(position); 

      // chuyển thông tin này qua bên phần MENU 
      j.putExtra("url", url); 
      j.putExtra("address", address); 
      j.putExtra("mahoadon", mahoadon); 
      j.putExtra("phone", phone); 
      j.putExtra("ID", iddelivery); 
      mContext.startActivity(j); 
     } 
    }); 
} 

}

类主要

public class Invoice extends Activity { 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.invoice); 
    mDb.openDB(); 
     Cursor mCursor = mDb.getAllInvoice(IDDelivery); 
     if (mCursor.moveToFirst()) { 
      do { 

       LoadListView load=new LoadListView(Invoice.this, mCursor.getString(1), mCursor.getString(2) ,mCursor.getString(3), mCursor.getString(4), mCursor.getString(5), IDDelivery); 
       load.loaddatalistview(); 

      } while (mCursor.moveToNext()); 
      //loaddatalistview(); 
     } 
     mDb.closeDB(); 
}

错误通知

12-25 14:03:38.033: W/System.err(21335): java.lang.NullPointerException 
12-25 14:03:38.041: W/System.err(21335): at Support.LoadListView.<init>(LoadListView.java:23) 
12-25 14:03:38.041: W/System.err(21335): at com.longvan.saigonfleamarket.Invoice.workoffline(Invoice.java:226) 
12-25 14:03:38.041: W/System.err(21335): at com.longvan.saigonfleamarket.Invoice.onCreate(Invoice.java:65) 
12-25 14:03:38.041: W/System.err(21335): at android.app.Activity.performCreate(Activity.java:4465) 
12-25 14:03:38.041: W/System.err(21335): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1053) 
12-25 14:03:38.041: W/System.err(21335): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1934) 
12-25 14:03:38.041: W/System.err(21335): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995) 
12-25 14:03:38.041: W/System.err(21335): at android.app.ActivityThread.access$600(ActivityThread.java:128) 
12-25 14:03:38.041: W/System.err(21335): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161) 
12-25 14:03:38.041: W/System.err(21335): at android.os.Handler.dispatchMessage(Handler.java:99) 
12-25 14:03:38.041: W/System.err(21335): at android.os.Looper.loop(Looper.java:137) 
12-25 14:03:38.041: W/System.err(21335): at android.app.ActivityThread.main(ActivityThread.java:4514) 
12-25 14:03:38.041: W/System.err(21335): at java.lang.reflect.Method.invokeNative(Native Method) 
12-25 14:03:38.041: W/System.err(21335): at java.lang.reflect.Method.invoke(Method.java:511) 
12-25 14:03:38.041: W/System.err(21335): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 
12-25 14:03:38.041: W/System.err(21335): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 
12-25 14:03:38.041: W/System.err(21335): at dalvik.system.NativeStart.main(Native Method) 
12-25 14:03:38.041: I/System.out(21335): Workoffline!!!

来源

2012-12-25 Takeshi Pham

跟踪您的代码以找出哪条线路导致NullPointerException –

它清楚地显示在第23行中，您正在收到错误.... –

这行看起来不正确的，因为你想调用的方法的空对象：

ListView listview=(ListView)((Activity)mContext).findViewById(R.id.listView1);

这应该在构造函数，而不是来完成：

public class LoadListView { 
    // ... (declare ListView with other class variables) 
    ListView listview; 

public LoadListView(Context mContext, String name,String phone,String address,String url,String code, String ID) 
{ 
    // ... (setting other class variables) 
    this.listview = (ListView)((Activity)mContext).findViewById(R.id.listView1); 
}

来源

2012-12-25 07:24:12 Klarth

请检查您的线没有23按日志猫说，

我建议，你应该检查一下mContext不为空mContext != null

所以刚 “mContext” 的

ListView listview=(ListView)((Activity)mContext).findViewById(R.id.listView1);

前值

来源

2012-12-25 07:26:09 swiftBoy

在列表视图中加载数据

回答

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