空指針異常，而在列表視圖中填充數據

-1

我是新的android開發。我試圖創建一個應用程序，在該應用程序中從sql server中獲取數據並將其顯示在列表視圖中。我用edittext和複選框創建了一個自定義列表視圖。問題是來自服務器的數據不在列表中。我試圖解決很多次，但每次都出現相同的問題，即ResultSet爲空。我的代碼是.........對Model.java空指針異常，而在列表視圖中填充數據

代碼

public class Model { 

private String name; 
    private boolean selected; 
    private String score; 

    public Model(String name) { 
     this.name = name; 
     selected = false; 
     score="";   
    } 
    public String getName() { 
     return name;  
     } 

    public void setName(String name) { 
     this.name = name; 
     } 

    public boolean isSelected() { 
     return selected;  
     } 

    public void setSelected(boolean selected) {  
    this.selected = selected;  
    } 

    public String getScore() {  
    return score;  
    } 

    public void setScore(String score) { 
     this.score = score; 
     } 
    }

代碼適配器類

public class MyAdapter extends ArrayAdapter<Model> { 

private final List<Model> list; 
private final Activity context; 

public MyAdapter(Activity context, List<Model> list) 
{ 
    super(context, R.layout.row, list); 
    this.context = context;  
    this.list = list; 
    } 

static class ViewHolder 
{   
    protected TextView text; 
    protected CheckBox checkbox;   
    protected EditText scores;  
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) 
{   
    View view = null; 
    if (convertView == null) 
    {    
     LayoutInflater inflator = context.getLayoutInflater(); 

     view = inflator.inflate(R.layout.row, null); 

     final ViewHolder viewHolder = new ViewHolder(); 
     viewHolder.text = (TextView) view.findViewById(R.id.label);  
     viewHolder.scores=(EditText) view.findViewById(R.id.txtAddress);  
     viewHolder.scores.addTextChangedListener(new TextWatcher() 
     { 
      public void onTextChanged(CharSequence s, int start, int before, int count) {  
       Model element=(Model)viewHolder.scores.getTag();  
       element.setScore(s.toString());   
      }   
      public void beforeTextChanged(CharSequence s, int start, int count,int after) 
      {  
      }  
      public void afterTextChanged(Editable s) 
      {        
      } 
      });   
     viewHolder.checkbox = (CheckBox) view.findViewById(R.id.check); 
     viewHolder.checkbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { 
      public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) { 
       Model element = (Model) viewHolder.checkbox.getTag();  
       element.setSelected(buttonView.isChecked());   
       }   
      }); 
     viewHolder.checkbox.setTag(list.get(position));  
     viewHolder.scores.setTag(list.get(position)); 
     view.setTag(viewHolder); 
    } 
    else 
    { 
     view = convertView; 
     ((ViewHolder) view.getTag()).checkbox.setTag(list.get(position)); 
     ((ViewHolder) view.getTag()).scores.setTag(list.get(position)); 
     }     
     ViewHolder holder = (ViewHolder) view.getTag();  
     holder.text.setText(list.get(position).getName());  
     holder.scores.setText(list.get(position).getScore());  
     holder.checkbox.setChecked(list.get(position).isSelected());  
     return view; 

} 

}

MainActivity.java

public class MainActivity extends Activity { 
ListView listView; 
Button btnSave; 
Connection connect; 
    ArrayAdapter<Model> adapter; 
    List<Model> list = new ArrayList<Model>(); 

    public void initilize(){ 

     connect=CONN("sa","[email protected]","KULDEEP","122.160.255.218:1433"); 
    } 


    @SuppressLint("NewApi") 
    private Connection CONN(String user,String pass,String db,String server){ 
    StrictMode.ThreadPolicy policy=new StrictMode.ThreadPolicy.Builder().permitAll().build(); 
    StrictMode.setThreadPolicy(policy); 
    Connection conn=null; 
    String connUrl=null; 
    try{ 
    Class.forName("net.sourceforge.jtds.jdbc.Driver"); 
    connUrl="jdbc:jtds:sqlserver://" + server + ";" + "databaseName=" + db + ";user=" + user + ";password=" + pass + ";"; 
    conn=DriverManager.getConnection(connUrl); 
    }catch(SQLException se){ 
     Log.e("ERROR", se.getMessage()); 
    }catch(ClassNotFoundException cl){ 
     Log.e("ERROR", cl.getMessage()); 
    }catch(Exception e){ 
     Log.e("ERROR", e.getMessage()); 
    } 

    return conn; 

     } 

    public void onCreate(Bundle icicle) { 
     super.onCreate(icicle); 
     setContentView(R.layout.main); 

     listView = (ListView) findViewById(R.id.my_list); 
     btnSave = (Button)findViewById(R.id.btnSave); 
     adapter = new MyAdapter(this,getModel()); 
     listView.setAdapter(adapter); 
     if(list.isEmpty()){ 
      Toast.makeText(getApplicationContext(), "kuldeep", Toast.LENGTH_LONG).show(); 
     } 

     btnSave.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 

       for (int i = 0; i < list.size(); i++) { 
        Toast.makeText(getBaseContext(), "Name : "+list.get(i).getName() +" Selected: "+list.get(i).isSelected()+"address: "+list.get(i).getScore().toString(), Toast.LENGTH_SHORT).show(); 

       } 
      } 
     }); 
    } 


    private List<Model> getModel() { 
     ResultSet rs; 
     try{ 
     Statement smt=connect.createStatement(); 
     rs=smt.executeQuery("select * from friends1"); 
     while(rs.next()){ 
      //Toast.makeText(getApplicationContext(), "0000", Toast.LENGTH_LONG).show(); 
      list.add(new Model(rs.getString("name"))); 
     } 
     }catch(Exception e){ 
      e.printStackTrace(); 
     } 
       return list; 
    } 
}

main.xml

<?xml version="1.0" encoding="utf-8"?> 
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" > 

    <ListView 
    android:id="@+id/my_list" 
    android:layout_width="fill_parent" 
    android:layout_height="250px" /> 
    <Button 
    android:text="Save" 
    android:id="@+id/btnSave" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"/> 

    </LinearLayout>

row.xml

<?xml version="1.0" encoding="utf-8"?> 
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal" > 

    <TextView 
    android:id="@+id/label" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="@+id/label" 
    android:textSize="30sp"/> 

    <CheckBox 
    android:id="@+id/check" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"/> 
    <EditText 
    android:text="" 
    android:id="@+id/txtAddress" 
    android:layout_width="150px" 
    android:layout_height="wrap_content"/> 
    </LinearLayout>

如果任何一個請建議我究竟是什麼問題... 如何在RS獲得價值正確的解決方案。

logcat按摩。

08-20 14:33:41.173: W/System.err(717): java.lang.NullPointerException 
08-20 14:33:41.173: W/System.err(717): at com.kuldeep.mylistedittext.MainActivity.getModel(MainActivity.java:92) 
08-20 14:33:41.173: W/System.err(717): at com.kuldeep.mylistedittext.MainActivity.onCreate(MainActivity.java:69) 
08-20 14:33:41.173: W/System.err(717): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
08-20 14:33:41.183: W/System.err(717): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 
08-20 14:33:41.183: W/System.err(717): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
08-20 14:33:41.183: W/System.err(717): at android.app.ActivityThread.access$1500(ActivityThread.java:117)

08-20 14：33：41.183：W/System.err的（717）：在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:931）

來源

2013-08-20 12345

安置自己的堆棧跟蹤也請！ – Pavlos

嘗試發佈您的日誌貓，以便我們可以輕鬆找到問題的根源。 –

我已經寫logcat味精。 – 12345

視圖保持器的方法應該像下面的代碼： -

if (convertView == null) { 
     convertView = mInflater.inflate(R.layout.list_item_icon_text, 
       parent, false); 
     holder = new ViewHolder(); 
     holder.text = (TextView) convertView.findViewById(R.id.text); 
     holder.icon = (ImageView) convertView.findViewById(R.id.icon); 

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

更改get view的代碼。

How to implement a view holder?

來源

2013-08-20 15:01:27 bashu

它不工作.... – 12345

在viewHolder.setTag（）和viewHolder.getTag（） – 12345

中得到錯誤現在嘗試它，它應該工作 – bashu

空指針異常，而在列表視圖中填充數據

回答

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