使用listview时，我有一个很大的问题，加载更多数据和远程图像。我的项目从json读取数据，当没有调用ImageLoader成功工作时
但是当我使用它时会返回致命错误 我在///错误和///错误之间有一个文本标记块 我的代码在这里：
package com.prgguru.android;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.AbsListView.OnScrollListener;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import org.json.JSONArray;
import org.json.JSONObject;
import org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.PropertyInfo;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapPrimitive;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransportSE;
import com.example.webserviceactivity.R;
public class ListViewActivity extends Activity
{
ListView mListView;
String worldData = "", adsValues[], strProduce, adsResult = "" , maxId="", subject = "",description = "", guild = "", section = "", avenue = "", shoppingCenter = "", tel = "", mobile = "", img = "";
JSONObject jsonOb;
JSONArray jsonArr;
JSONObject jsonOne;
List<HashMap<String, String>> searchResult = new ArrayList<HashMap<String,String>>();
HashMap<String, String> searchResultTemp;
Integer intKind = 0, intGuild = 0, intSection = 0, intAvenue = 0, intShoppingCenter = 0;
public static final int progress_bar_type = 0;
private ProgressDialog pDialog;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.searchresult);
Intent intent = getIntent();
if(intent != null) worldData = intent.getStringExtra("adsResult");
adsValues = worldData.split("Ý");
String[] strValueTemp = adsValues[1].split("ï");
intKind = Integer.parseInt(strValueTemp[0]);
intGuild = Integer.parseInt(strValueTemp[1]);
intSection = Integer.parseInt(strValueTemp[2]);
intAvenue = Integer.parseInt(strValueTemp[3]);
intShoppingCenter = Integer.parseInt(strValueTemp[4]);
strProduce = strValueTemp[5];
if(strValueTemp[5].compareTo("n") == 0) strProduce = "";
getlList(adsValues[0]);
///////////////////////////////////////////////////////////////
mListView.setOnScrollListener(new OnScrollListener() {
public void onScrollStateChanged(AbsListView view,
int scrollState) { // TODO Auto-generated method stub
int threshold = 1;
int position = mListView.getLastVisiblePosition();
int count = mListView.getCount();
if (scrollState == SCROLL_STATE_IDLE) {
if (mListView.getLastVisiblePosition() >= count - threshold) {
getAdsResult(intKind, intGuild, intSection, intAvenue, intShoppingCenter, strProduce, Integer.parseInt(maxId));
getlList(adsResult);
mListView.setSelection(position);
}
}
}
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub
}
});
}
//////////////////////////////////////////////////////////////////////////////////////////////////////
public void getlList(String json)
{
try
{
jsonOb = new JSONObject(json);
jsonArr = jsonOb.getJSONArray("adsResults");
for(int i = 0; i < jsonArr.length(); i++)
{
jsonOne = jsonArr.getJSONObject(i);
///////////////////////////////////////////////
maxId = jsonOne.getString("id");
subject = jsonOne.getString("subject");
description = jsonOne.getString("desc");
guild = jsonOne.getString("guildStr");
tel = jsonOne.getString("tel");
if(tel.compareTo("") != 0) tel = tel + " -- ";
mobile = jsonOne.getString("mobile");
if(shoppingCenter.compareTo("0") == 0)
{
section = jsonOne.getString("sectionStr");
avenue = jsonOne.getString("avenueStr");
description = "\n" + description + "\n" + "صنف : " + guild + " -- پاساژ : " + shoppingCenter + " -- " + tel + mobile;
}
else
{
shoppingCenter = jsonOne.getString("shoppingCenterStr");
description = "\n" + description + "\n" + "صنف : " + guild + " -- منطقه : " + section + "(" + avenue + ")" + " -- " + tel + mobile;
}
description += "\n";
img = jsonOne.getString("img");
searchResultTemp = new HashMap<String, String>();
searchResultTemp.put("subject", subject);
searchResultTemp.put("description", description);
searchResultTemp.put("img", String.valueOf(R.drawable.s));
///////////////////////////////////////////
searchResult.add(searchResultTemp);
}
String[] from = {"subject","img","description"};
int[] to = {R.id.tv_subject,R.id.iv_pic, R.id.tv_details};
/////////////////////////////////////////////////////////////////////
mListView = (ListView) findViewById(R.id.lv_Result);
mListView.setOnItemClickListener(new OnItemClickListener()
{
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
int pos = mListView.getSelectedItemPosition();
Toast.makeText(ListViewActivity.this, String.valueOf(pos), Toast.LENGTH_LONG).show();
}
});
/////////////////////////////////////////////////////////
SimpleAdapter adapter = new SimpleAdapter(ListViewActivity.this,searchResult,R.layout.listview, from, to);
mListView.setAdapter(adapter);
/////////////////////////////////////////////////////////////////////////////////////////////
///error
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("img");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
hm.put("img",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
///error
}
catch(Exception ex)
{
Toast.makeText(ListViewActivity.this, ex.getMessage(), Toast.LENGTH_LONG).show();
}
//////////////////////////////////////////////////////////////////////////////////////////////////
}
//////////////////////////////////////////////////////////////////////////////////////////////////////
public void getAdsResult(int intKind, int intGuild, int intSection, int intAveune,int intShoppingCenter, String produce, int idClause)
{
//Create request
SoapObject request = new SoapObject("http://admin.arabbros.com/", "searchAdsList");
//Create envelope
PropertyInfo requestPI = new PropertyInfo();
requestPI.setName("kind");
requestPI.setValue(intKind);
requestPI.setType(int.class);
request.addProperty(requestPI);
requestPI = new PropertyInfo();
/////////////////////////////////////////
requestPI.setName("guild");
requestPI.setValue(intGuild);
requestPI.setType(int.class);
request.addProperty(requestPI);
requestPI = new PropertyInfo();
/////////////////////////////////////////
requestPI.setName("section");
requestPI.setValue(intSection);
requestPI.setType(int.class);
request.addProperty(requestPI);
requestPI = new PropertyInfo();
/////////////////////////////////////////
requestPI.setName("avenue");
requestPI.setValue(intAveune);
requestPI.setType(int.class);
request.addProperty(requestPI);
requestPI = new PropertyInfo();
/////////////////////////////////////////
requestPI.setName("shoppingCenter");
requestPI.setValue(intShoppingCenter);
requestPI.setType(int.class);
request.addProperty(requestPI);
requestPI = new PropertyInfo();
/////////////////////////////////////////
requestPI.setName("produce");
requestPI.setValue(produce);
requestPI.setType(String.class);
request.addProperty(requestPI);
requestPI = new PropertyInfo();
/////////////////////////////////////////
requestPI.setName("idClause");
requestPI.setValue(idClause);
requestPI.setType(int.class);
request.addProperty(requestPI);
SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
envelope.dotNet = true;
//Set output SOAP object
envelope.setOutputSoapObject(request);
//Create HTTP call object
HttpTransportSE androidHttpTransport = new HttpTransportSE("http://admin.arabbros.com/MobileWs.asmx");
try {
//Invole web service
androidHttpTransport.call("http://admin.arabbros.com/searchAdsList", envelope);
//Get the response
SoapPrimitive response = (SoapPrimitive) envelope.getResponse();
adsResult = response.toString();
} catch (Exception e) {
adsResult = "0";
}
}
///////////////////////////////////////////////////////////////////////////////////////////////
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
@Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream=null;
String imgUrl = (String) hm[0].get("img");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+position+".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
//Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("img",tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position",position);
// Returning the HashMap object containing the image path and position
return hmBitmap;
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(HashMap<String, Object> result) {
// Getting the path to the downloaded image
String path = (String) result.get("img");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter ) mListView.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
// Overwriting the existing path in the adapter
hm.put("img",path);
// Noticing listview about the dataset changes
adapter.notifyDataSetChanged();
}
}
}
答案 0 :(得分：0)
好的，过了一会儿，我有以下东西给你。由于这不是在评论中讨论的好方法，我将在这里发布。
首先：
你的代码中有这个：searchResultTemp.put（＆＃34; img＆＃34;，String.valueOf（R.drawable.s））; （你提供给我的代码），这将设置你的＆＃34; img＆＃34;值到ID字符串（不是有效的URL）。这将导致LoaderTask的doInBackground方法失败并返回null值。在你的onPostExecute中，你没有检查null返回，然后它导致你的应用程序失败。请更改此（put（＆＃34; img＆＃34;，img），例如，其中img是你从json获得的url）。
第二
你的json有＆＃34; img＆＃34;属性，但其值不是有效的http url（例如，＆＃34; dariran.com/ads/mobile/1.jpg"），因此，您的任务再次无法执行http请求，将给出null返回。请从您的服务器或任何将返回Json结果的内容中修复它。
第三
这是您启动listview的方式：您定义了一个getlList方法，添加了一个try / catch并将listview启动代码放入其中。一旦您的解析过程失败，例如，某些条目不存在，您的代码将抛出异常，您的列表视图将永远不会启动。这是一个糟糕的方法。我建议您在onCreate方法中启动所有基于视图/活动的实例。