ListView每次创建片段时都会显示重复的数据

这里是我的片段的代码，我在asynctask中访问一个web服务来获取数据并在列表中显示，我也懒加载图像。当片段创建为第一次输出是正确的，它会在列表中显示7个项目，问题是当片段在被销毁后重新创建数据被重复时，即如果它第二次启动，则列表显示14个项目（早期7个项目7次再次被提取），每当它重新创建时，都会发生这种情况。列表中的项目比以前多了7个。尽管在On destroy中，我清除了适配器的数据，而adapter.getCount（）显示为0，但仍然存在此问题。ListView每次创建片段时都会显示重复的数据

public class ServiceCarListFragment extends Fragment { 

private String url; 
private ArrayList<CarDetail> carDetailList = new ArrayList<CarDetail>(); 
private CarListAdapter adapter; 
private ListView mList ; 
private ProgressDialog progressDialog; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onCreate(savedInstanceState); 
    Log.d("Services", "On Create"); 
    url = getActivity().getIntent().getStringExtra("url"); 
    adapter = new CarListAdapter(getActivity() , carDetailList); 
    new DownloadCarDetail().execute(url); 

} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
     Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    Log.d("Services", "On CreateView"); 
    View v = inflater.inflate(R.layout.fragment_service_car_list,  container,false); 
    mList = (ListView)v.findViewById(R.id.list); 
    mList.setAdapter(adapter);  
    return v; 
} 

class DownloadCarDetail extends AsyncTask<String, String, ArrayList<CarDetail>>{ 



    @Override 
    protected void onPreExecute() { 
     // TODO Auto-generated method stub 
     super.onPreExecute(); 
     progressDialog = ProgressDialog.show(getActivity(), null, "Loading...",true); 

    } 

    @Override 
    protected ArrayList<CarDetail> doInBackground(String... params) { 
     // TODO Auto-generated method stub 
     ArrayList<CarDetail> carDetailList = JsonParser.parseJson(params[0]); 
     return carDetailList; 
    } 

    @Override 
    protected void onPostExecute(ArrayList<CarDetail> carDetailList) { 
     // TODO Auto-generated method stub 
     //ServiceCarListFragment.this.carDetailList = carDetailList; 
     //adapter = new CarListAdapter(getActivity(),ServiceCarListFragment.this.carDetailList); 
     //mList.setAdapter(adapter); 
     progressDialog.dismiss(); 
     ServiceCarListFragment.this.carDetailList.addAll(carDetailList); 
     adapter.notifyDataSetChanged(); 
     for (CarDetail car : carDetailList) { 
      // START LOADING IMAGES FOR EACH STUDENT 
      car.loadImage(adapter); 

    } 

} 

} 

@Override 
public void onDestroy() { 
    // TODO Auto-generated method stub 
    super.onDestroy(); 
    carDetailList.clear(); 
    adapter.notifyDataSetChanged(); 
    Log.d("Services", String.valueOf(adapter.getCount())); 
} 

@Override 
public void onDestroyView() { 
    // TODO Auto-generated method stub 
    super.onDestroyView(); 
    Log.d("Services", "On DestroyView"); 
} 

@Override 
public void onDetach() { 
    // TODO Auto-generated method stub 
    super.onDetach(); 
    Log.d("Services", "On Detach"); 
} 

@Override 
public void onAttach(Activity activity) { 
    // TODO Auto-generated method stub 
    super.onAttach(activity); 
    Log.d("Services", "On Attach"); 
} 

}

这是我使用

public class CarListAdapter extends BaseAdapter { 

private ArrayList<CarDetail> items = new ArrayList<CarDetail>(); 
private Context context; 


public CarListAdapter(Context context , ArrayList<CarDetail> items) { 
    super(); 
    this.context = context; 
    this.items = items; 

} 

@Override 
public int getCount() { 
    // TODO Auto-generated method stub 
    return items.size(); 
} 

@Override 
public Object getItem(int position) { 
    // TODO Auto-generated method stub 
    return items.get(position); 
} 

@Override 
public long getItemId(int position) { 
    // TODO Auto-generated method stub 
    return position; 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    // TODO Auto-generated method stub 
    Log.d("Inside", "GetView"); 
    LayoutInflater mInflater = (LayoutInflater)context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE); 
    ViewHolder holder = null; 
    CarDetail car = items.get(position); 

    if (convertView == null) { 
      convertView = mInflater.inflate(R.layout.car_list_row, parent , false); 
      holder = new ViewHolder(); 
      holder.tvCarName = (TextView) convertView.findViewById(R.id.tvCarName); 
      holder.tvDailyPriceValue = (TextView) convertView.findViewById(R.id.tvWeeklyPriceValue); 
      holder.tvWeeklyPriceValue = (TextView) convertView.findViewById(R.id.tvWeeklyPriceValue); 
      holder.imgCar = (ImageView) convertView.findViewById(R.id.imgCar); 
      convertView.setTag(holder); 
    } 
    else { 
      holder = (ViewHolder) convertView.getTag(); 
     } 

    holder.tvCarName.setText(car.getCarName()); 
     if (car.getImage() != null) { 
      holder.imgCar.setImageBitmap(car.getImage()); 
     } else { 
       // MY DEFAULT IMAGE 
      holder.imgCar.setImageResource(R.drawable.ic_action_call); 
     } 

    return convertView; 
} 

static class ViewHolder { 

      TextView tvCarName; 
      TextView tvDailyPriceValue; 
      TextView tvWeeklyPriceValue; 
      ImageView imgCar; 
     } 

}

这个自定义适配器模型类

public class CarDetail { 

private String carId; 
private String carName; 
private String imageUrl; 
private String thumbUrl; 
private String dailyPrice; 
private String weeklyPrice; 
private String weekendPrice; 
private String deposit; 
private String minimumAge; 
private String color; 
private String make; 
private String location; 
private String bodyType; 
private String fuelType; 
private String transmission; 
private String carType; 
private String model; 
private String description; 
private Bitmap image; 
private Bitmap thumbImage; 
private CarListAdapter carAdapter; 

public CarDetail() { 
    super(); 
    // TODO Auto-generated constructor stub 
} 

public CarDetail(String carId, String carName, String imageUrl, 
     String thumbUrl, String dailyPrice, String weeklyPrice, 
     String weekendPrice, String deposit, String minimumAge, 
     String color, String make, String location, String bodyType, 
     String fuelType, String transmission, String carType, String model, 
     String description) { 
    super(); 
    this.carId = carId; 
    this.carName = carName; 
    this.imageUrl = imageUrl; 
    this.thumbUrl = thumbUrl; 
    this.dailyPrice = dailyPrice; 
    this.weeklyPrice = weeklyPrice; 
    this.weekendPrice = weekendPrice; 
    this.deposit = deposit; 
    this.minimumAge = minimumAge; 
    this.color = color; 
    this.make = make; 
    this.location = location; 
    this.bodyType = bodyType; 
    this.fuelType = fuelType; 
    this.transmission = transmission; 
    this.carType = carType; 
    this.model = model; 
    this.description = description; 

    // TO BE LOADED LATER - OR CAN SET TO A DEFAULT IMAGE 
    this.image = null; 
    this.thumbImage = null; 
} 

public String getCarId() { 
    return carId; 
} 

public void setCarId(String carId) { 
    this.carId = carId; 
} 

public String getCarName() { 
    return carName; 
} 

public void setCarName(String carName) { 
    this.carName = carName; 
} 

public String getImageUrl() { 
    return imageUrl; 
} 

public void setImageUrl(String imageUrl) { 
    this.imageUrl = imageUrl; 
} 

public String getThumbUrl() { 
    return thumbUrl; 
} 

public void setThumbUrl(String thumbUrl) { 
    this.thumbUrl = thumbUrl; 
} 

public String getDailyPrice() { 
    return dailyPrice; 
} 

public void setDailyPrice(String dailyPrice) { 
    this.dailyPrice = dailyPrice; 
} 

public String getWeeklyPrice() { 
    return weeklyPrice; 
} 

public void setWeeklyPrice(String weeklyPrice) { 
    this.weeklyPrice = weeklyPrice; 
} 

public String getWeekendPrice() { 
    return weekendPrice; 
} 

public void setWeekendPrice(String weekendPrice) { 
    this.weekendPrice = weekendPrice; 
} 

public String getDeposit() { 
    return deposit; 
} 

public void setDeposit(String deposit) { 
    this.deposit = deposit; 
} 

public String getMinimumAge() { 
    return minimumAge; 
} 

public void setMinimumAge(String minimumAge) { 
    this.minimumAge = minimumAge; 
} 

public String getColor() { 
    return color; 
} 

public void setColor(String color) { 
    this.color = color; 
} 

public String getMake() { 
    return make; 
} 

public void setMake(String make) { 
    this.make = make; 
} 

public String getLocation() { 
    return location; 
} 

public void setLocation(String location) { 
    this.location = location; 
} 

public String getBodyType() { 
    return bodyType; 
} 

public void setBodyType(String bodyType) { 
    this.bodyType = bodyType; 
} 

public String getFuelType() { 
    return fuelType; 
} 

public void setFuelType(String fuelType) { 
    this.fuelType = fuelType; 
} 

public String getTransmission() { 
    return transmission; 
} 

public void setTransmission(String transmission) { 
    this.transmission = transmission; 
} 

public String getCarType() { 
    return carType; 
} 

public void setCarType(String carType) { 
    this.carType = carType; 
} 

public String getModel() { 
    return model; 
} 

public void setModel(String model) { 
    this.model = model; 
} 

public String getDescription() { 
    return description; 
} 

public void setDescription(String description) { 
    this.description = description; 
} 

public Bitmap getImage() { 
    return image; 
} 

public void setImage(Bitmap image) { 
    this.image = image; 
} 

public Bitmap getThumbImage() { 
    return thumbImage; 
} 

public void setThumbImage(Bitmap thumbImage) { 
    this.thumbImage = thumbImage; 
} 

public void loadImage(CarListAdapter carAdapter) { 
     // HOLD A REFERENCE TO THE ADAPTER 
     this.carAdapter = carAdapter; 
     if (thumbUrl != null && !thumbUrl.equals("")) { 
      new ImageLoadTask().execute(thumbUrl); 
     } 
} 

    // ASYNC TASK TO AVOID CHOKING UP UI THREAD 
    private class ImageLoadTask extends AsyncTask<String, String, Bitmap> { 

     @Override 
     protected void onPreExecute() { 
      Log.i("ImageLoadTask", "Loading image..."); 
     } 

     // PARAM[0] IS IMG URL 
     protected Bitmap doInBackground(String... param) { 
      Log.i("ImageLoadTask", "Attempting to load image URL: " + param[0]); 
      try { 
       Bitmap b = JsonParser.downloadBitmap(param[0]); 
       return b; 
      } catch (Exception e) { 
       e.printStackTrace(); 
       return null; 
      } 
     } 

     protected void onProgressUpdate(String... progress) { 
      // NO OP 
     } 

     protected void onPostExecute(Bitmap ret) { 
      if (ret != null) { 
       Log.i("ImageLoadTask", "Successfully loaded " + carName + " image"); 
       image = ret; 
       if (carAdapter != null) { 
        // WHEN IMAGE IS LOADED NOTIFY THE ADAPTER 
        carAdapter.notifyDataSetChanged(); 
       } 
      } else { 
       Log.e("ImageLoadTask", "Failed to load " + carName + " image"); 
      } 
     } 
    }

来源

2013-05-03 Ravi

您需要在下次调用异步方法之前清除ArrayList数据。在你的情况下，它将是carDetailLis.clear()new DownloadCarDetail().execute(url);或只是检查流量并清除它。

来源

2013-05-03 11:16:51

没有工作我清除了列表并通知适配器..still同样的问题。 – Ravi 2013-05-03 11:26:24

你有没有通过调试或日志检查你的代码的流程，检查它在ArrayList中添加数据的位置，因为我最近有类似的问题，这是一个很好的方法来解决它... – 2013-05-03 11:31:26

雅它工作，但我清除它在onPostExecute方法的结束。你可以解释为什么发生这种情况，我的意思是carDetailList应该在onPostExecute方法之外自动销毁 – Ravi 2013-05-03 11:46:56

我建议你修改

ServiceCarListFragment.this.carDetailList.addAll(carDetailList);

在

ServiceCarListFragment.this.carDetailList = new ArrayList... 
carDetailList.addAll

而且您应该验证carDetailList的长度在多次调用服务器之后是否相同。

来源

2013-05-03 11:11:58 FrancescoAzzola

ListView每次创建片段时都会显示重复的数据

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