ListView垂直滚动时隐藏图片

Question

我是第一个执行Android应用程序的人，我的应用程序涉及到汽车，在公司选择活动中我有ListView问题。 在第一次是这样的：

但是，当滚动，显示我的默认图标，而不是标志

我怎么能解决这个问题？ 在此代码中，我从本地json数组中获取数据并发送到自定义列表以供表格显示。下面的代码是我viewallcompnay活动：

package ir.database; 

import java.io.BufferedReader; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import java.util.ArrayList; 

import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import android.app.Activity; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.widget.ListView; 

public class ViewAllCompany extends Activity { 
String url = "http://192.168.1.206/androhp/companylist.php"; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    setContentView(R.layout.view_all_company); 
    LoadAllCompany lap = new LoadAllCompany(); 
    lap.execute(url); 
} 

private class LoadAllCompany extends AsyncTask<String, String, String> { 
    private ArrayList<String> urlData; 
    private ListView list; 

    private InputStream getStreamFromURL(String urlString, String method) { 
     try { 
      URL url = new URL(urlString); 
      HttpURLConnection huc = (HttpURLConnection) url 
        .openConnection(); 
      huc.setRequestMethod(method); 

      huc.connect(); 

      return huc.getInputStream(); 
     } catch (Exception e) { 
      return null; 
     } 

    } 

    private String streamToString(InputStream is) { 
     String result = ""; 
     String line = null; 

     try { 
      BufferedReader br = new BufferedReader(
        new InputStreamReader(is)); 
      while ((line = br.readLine()) != null) { 
       result = line + "\n"; 
      } 
     } catch (Exception e) { 
     } 

     return result; 
    } 

    protected String doInBackground(String... args) { 
     InputStream jsonStream = getStreamFromURL(args[0], "GET"); 
     String jsonString = streamToString(jsonStream); 
     urlData = parseJSON(jsonString); 
     return null; 
    } 

    private ArrayList<String> parseJSON(String JSONString) { 
     try { 
      ArrayList<String> result = new ArrayList<String>(); 
      JSONObject jo = new JSONObject(JSONString); 
      JSONArray allpersons = jo.getJSONArray("companylist"); 
      for (int i = 0; i < allpersons.length(); i++) { 
       JSONObject object = allpersons.getJSONObject(i); 
       String objString = ""; 
       objString = object.getString("name") + "," 
         + object.getString("picture") + "," 
         + object.getInt("id"); 
       result.add(objString); 
      } 
      return result; 

     } catch (JSONException e) { 
      return null; 
     } 
    } 

    protected void onPostExecute(String file_url) { 
     String[] companyname = new String[urlData.size()]; 
     String[] imageUrl = new String[urlData.size()]; 
     String[] id = new String[urlData.size()]; 
     int i = 0; 
     for (String s : urlData) { 
      String[] split = s.split(","); 
      id[i] = split[2]; 
      companyname[i] = split[0]; 
      imageUrl[i] = "http://lgapps.karnotech.ir/takhtegaz/images/companylogo/" 
        + split[2] + "/" + split[1]; 
      i++; 
     } 

     list = (ListView) findViewById(R.id.list); 
     CustomList adapter = new CustomList(ViewAllCompany.this, 
       companyname, imageUrl, id); 
     list.setAdapter(adapter); 
     adapter.notifyDataSetChanged(); 
    } 
} 
} 

viewallcompany XML布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:paddingBottom="@dimen/activity_vertical_margin" 
android:paddingLeft="@dimen/activity_horizontal_margin" 
android:paddingRight="@dimen/activity_horizontal_margin" 
android:paddingTop="@dimen/activity_vertical_margin" 
tools:context=".View_all_company" > 

<ListView 
    android:id="@+id/list" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerVertical="true" 
    android:scrollingCache="true" > 

</ListView> 

，这代码是我customlist：

package ir.database; 

import android.app.Activity; 
import android.content.Intent; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.ImageView; 
import android.widget.TextView; 

public class CustomList extends ArrayAdapter<String> { 
private final Activity context; 
private final String[] companyname; 
private final String[] imageUrl; 
private final String[] id; 
private ImageLoader imgLoader; 

public CustomList(Activity context, String[] companyname, 
     String[] imageUrl, String[] id) { 
    super(context, R.layout.single_list, companyname); 
    this.context = context; 
    this.companyname = companyname; 
    this.id = id; 
    this.imageUrl = imageUrl; 

} 

@Override 
public View getView(int position, View view, ViewGroup parent) { 
    LayoutInflater inflater = context.getLayoutInflater(); 
    View rowView = inflater.inflate(R.layout.single_list, null, true); 

    TextView txtTitle = (TextView) rowView.findViewById(R.id.txt); 

    txtTitle.setId(Integer.parseInt(this.id[position])); 

    txtTitle.setOnClickListener(new View.OnClickListener() { 
     public void onClick(View v) { 
      Intent intent = new Intent(context, Cars.class); 
      intent.putExtra("carId", v.getId()); 
      context.startActivity(intent); 
     } 
    }); 

    txtTitle.setText(companyname[position]); 

    ImageView imageView = (ImageView) rowView.findViewById(R.id.img); 

    imgLoader = new ImageLoader(context); 
    imgLoader.DisplayImage(imageUrl[position], imageView); 

    return rowView; 
} 

}

丘斯托mlist XML布局：

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent"> 

<TableRow android:gravity="right"> 

<ImageView 
    android:id="@+id/img" 
    android:layout_width="30dp" 
    android:layout_height="30dp" /> 
<TextView 
    android:id="@+id/txt" 
    android:layout_width="90dp" 
    android:layout_height="30dp" 
    android:clickable="true" 
    android:onClick="onClick" 
    /> 
</TableRow> 

Answer 1

我觉得getView方法的实现可以通过一些变化来优化; 您必须使用setTag和getTag以避免重复查找视图。例如像这样：

@Override 
public View getView(final int position, View convertView, ViewGroup parent) { 
    final ViewHolder mHolder; 
    if (convertView == null) { 
     convertView = mInflater.inflate(R.layout.list_menu, null); 
     mHolder = new ViewHolder(); 

     mHolder.mText=(TextView) convertView.findViewById(R.id.appName); 
     mHolder.mImage=(ImageView) convertView.findViewById(R.id.appIcon); 
     mHolder.mCheckBox=(CheckBox) convertView.findViewById(R.id.mCheckbox); 

     convertView.setTag(mHolder); 

    } else { 
     mHolder = (ViewHolder) convertView.getTag(); 
    } 

    return convertView; 
} 

private class ViewHolder { 
    private TextView mText; 
    private ImageView mImage; 
    private CheckBox mCheckBox; 

} 

当然，我建议你也看看这个答案了。

https://stackoverflow.com/a/15415784/2101822

https://stackoverflow.com/a/19019905/2101822