我有一个asyncTask，在方法doInBackground中我有两个for循环，一个用于我创建的每个节点列表。在第一个for循环中，它完美地运行并返回我想要的内容。尽管第二个几乎是克隆，但nodeList是唯一改变的东西，应用程序崩溃了。什么可能导致这次崩溃？
这是for循环代码：
NodeList nl = doc.getElementsByTagName(KEY_FUEL);
NodeList nl2 = doc2.getElementsByTagName(KEY_FUEL);
// looping through all item nodes <item>
for (int i = 0; i < nl.getLength(); i++)
{
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
HashMap<String, String> map1 = new HashMap<String, String>();
HashMap<String, String> map2 = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_HIGHEST, "Highest units = " + parser.getValue(e, KEY_HIGHEST));
Log.v(TAG, "indexmap=" + map);
map1.put(KEY_AVERAGE, "Average units = " + parser.getValue(e, KEY_AVERAGE));
Log.v(TAG, "indexmi=" + map1);
map2.put(KEY_LOWEST, "Lowest units = " +parser.getValue(e, KEY_LOWEST));
Log.v(TAG, "indexmi=" + map2);
// adding HashList to ArrayList
menuItems.add(map);
Log.v(TAG, "indexmi=" + menuItems);
menuItems2.add(map1);
Log.v(TAG, "indexmi2=" + menuItems2);
menuItems3.add(map2);
Log.v(TAG, "indexmi3=" + menuItems3);
menuItemsString = menuItems.toString();
menuItemsString2 = menuItems2.toString();
menuItemsString3 = menuItems3.toString();
}
for (int i = 0; i < nl2.getLength(); i++)
{
Log.v(TAG, "indexnl2=" + nl2.getLength());
// creating new HashMap
HashMap<String, String> map3 = new HashMap<String, String>();
HashMap<String, String> map4 = new HashMap<String, String>();
HashMap<String, String> map5 = new HashMap<String, String>();
Element e = (Element) nl2.item(i);
// adding each child node to HashMap key => value
map3.put(KEY_HIGHEST, "Highest units = " + parser.getValue(e, KEY_HIGHEST));
Log.v(TAG, "indexmaps3=" + map3);
map4.put(KEY_AVERAGE, "Average units = " + parser.getValue(e, KEY_AVERAGE));
Log.v(TAG, "indexmaps4=" + map4);
map5.put(KEY_LOWEST, "Lowest units = " +parser.getValue(e, KEY_LOWEST));
Log.v(TAG, "indexmaps5=" + map5);
// adding HashList to ArrayList
menuItems4.add(map3);
Log.v(TAG, "indexmi4=" + menuItems4);
menuItems5.add(map4);
Log.v(TAG, "indexmi5=" + menuItems5);
menuItems6.add(map5);
Log.v(TAG, "indexmi6=" + menuItems6);
menuItemsString4 = menuItems4.toString();
menuItemsString5 = menuItems5.toString();
menuItemsString6 = menuItems6.toString();
}
这是错误logcat：
08-21 14:56:25.611: E/Trace(1851): error opening trace file: No such file or directory (2)
08-21 14:56:46.131: E/AndroidRuntime(1851): FATAL EXCEPTION: AsyncTask #1
08-21 14:56:46.131: E/AndroidRuntime(1851): java.lang.RuntimeException: An error occured while executing doInBackground()
08-21 14:56:46.131: E/AndroidRuntime(1851): at android.os.AsyncTask$3.done(AsyncTask.java:299)
08-21 14:56:46.131: E/AndroidRuntime(1851): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
08-21 14:56:46.131: E/AndroidRuntime(1851): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
08-21 14:56:46.131: E/AndroidRuntime(1851): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
08-21 14:56:46.131: E/AndroidRuntime(1851): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
08-21 14:56:46.131: E/AndroidRuntime(1851): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
08-21 14:56:46.131: E/AndroidRuntime(1851): at java.lang.Thread.run(Thread.java:856)
08-21 14:56:46.131: E/AndroidRuntime(1851): Caused by: java.lang.NullPointerException
08-21 14:56:46.131: E/AndroidRuntime(1851): at org.me.myandroidstuff.ComparePrices$asyncTaskCompare.doInBackground(ComparePrices.java:317)
08-21 14:56:46.131: E/AndroidRuntime(1851): at org.me.myandroidstuff.ComparePrices$asyncTaskCompare.doInBackground(ComparePrices.java:1)
08-21 14:56:46.131: E/AndroidRuntime(1851): at android.os.AsyncTask$2.call(AsyncTask.java:287)
08-21 14:56:46.131: E/AndroidRuntime(1851): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
08-21 14:56:46.131: E/AndroidRuntime(1851): ... 3 more
这是节点列表nl2长度，表明这不是for循环中的问题：
08-21 14:56:46.131: V/ComparePrices(1851): indexnl2=4
这是用于显示代码输出的logcat。正如你所看到的那样，第一个for循环正常工作，但不知怎的，第二个循环在它应该停止之前停止：
08-21 14:56:46.131: V/ComparePrices(1851): indexmi=[{Highest=Highest units = 133.1}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi2=[{Average=Average units = 128.4}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi3=[{Lowest=Lowest units = 124.7}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi=[{Highest=Highest units = 133.1}, {Highest=Highest units = 139.9}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi2=[{Average=Average units = 128.4}, {Average=Average units = 132.8}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi3=[{Lowest=Lowest units = 124.7}, {Lowest=Lowest units = 128.7}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi=[{Highest=Highest units = 133.1}, {Highest=Highest units = 139.9}, {Highest=Highest units = 141.9}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi2=[{Average=Average units = 128.4}, {Average=Average units = 132.8}, {Average=Average units = 136.9}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi3=[{Lowest=Lowest units = 124.7}, {Lowest=Lowest units = 128.7}, {Lowest=Lowest units = 132.9}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi=[{Highest=Highest units = 133.1}, {Highest=Highest units = 139.9}, {Highest=Highest units = 141.9}, {Highest=Highest units = 69.9}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi2=[{Average=Average units = 128.4}, {Average=Average units = 132.8}, {Average=Average units = 136.9}, {Average=Average units = 69.9}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi3=[{Lowest=Lowest units = 124.7}, {Lowest=Lowest units = 128.7}, {Lowest=Lowest units = 132.9}, {Lowest=Lowest units = 69.9}]
08-21 14:56:46.131: V/ComparePrices(1851): indexmi4=[{Highest=Highest units = 132.9}]
编辑：完整的doInBackground方法
protected String[] doInBackground(String...params)
{
String urlString = newFifthString;
String urlString2 = newEighthString;
String result = "";
String result2 = "";
InputStream anInStream = null;
InputStream anInStream2 = null;
int response = -1;
int response2 = -1;
URL url = null;
URL url2 = null;
try
{
url = new URL(urlString);
url2 = new URL(urlString2);
}
catch (MalformedURLException e)
{
// TODO Auto-generated catch block
return null;
}
URLConnection conn = null;
URLConnection conn2 = null;
try
{
conn = url.openConnection();
conn2 = url2.openConnection();
}
catch (IOException e)
{
// TODO Auto-generated catch block
return null;
}
// Check that the connection can be opened
if (!(conn instanceof HttpURLConnection && conn2 instanceof HttpURLConnection))
{
try
{
throw new IOException("Not an HTTP connection");
}
catch (IOException e)
{
// TODO Auto-generated catch block
return null;
}
}
try
{
// Open connection
HttpURLConnection httpConn = (HttpURLConnection) conn;
HttpURLConnection httpConn2 = (HttpURLConnection) conn2;
httpConn.setAllowUserInteraction(false);
httpConn.setInstanceFollowRedirects(true);
httpConn.setRequestMethod("GET");
httpConn.connect();
response = httpConn.getResponseCode();
httpConn2.setInstanceFollowRedirects(true);
httpConn2.setRequestMethod("GET");
httpConn2.connect();
response2 = httpConn.getResponseCode();
// Check that connection is OK
if (response == HttpURLConnection.HTTP_OK && response2 == HttpURLConnection.HTTP_OK )
{
// Connection is OK so open a reader
anInStream = httpConn.getInputStream();
anInStream2 = httpConn2.getInputStream();
InputStreamReader in= new InputStreamReader(anInStream);
InputStreamReader in2= new InputStreamReader(anInStream2);
BufferedReader bin= new BufferedReader(in);
BufferedReader bin2= new BufferedReader(in2);
// Read in the data from the RSS stream
String line = new String();
String line2 = new String();
while (( (line = bin.readLine())) != null)
{
result = result + line;
Log.v(TAG, "indexres=" + result);
}
while (( (line2 = bin2.readLine())) != null)
{
result2 = result2 + line2;
Log.v(TAG, "indexres2=" + result2);
}
}
menuItems = new ArrayList<HashMap<String, String>>();
menuItems2 = new ArrayList<HashMap<String, String>>();
menuItems3 = new ArrayList<HashMap<String, String>>();
menuItems4 = new ArrayList<HashMap<String, String>>();
menuItems4 = new ArrayList<HashMap<String, String>>();
menuItems6 = new ArrayList<HashMap<String, String>>();
Handler parser = new Handler();
String xml = result; // getting XML
String xml2 = result2;
Document doc = parser.getDomElement(xml);
Document doc2 = parser.getDomElement(xml2);
// getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_FUEL);
NodeList nl2 = doc2.getElementsByTagName(KEY_FUEL);
// looping through all item nodes <item>
for (int i = 0; i < nl.getLength(); i++)
{
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
HashMap<String, String> map1 = new HashMap<String, String>();
HashMap<String, String> map2 = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_HIGHEST, "Highest units = " + parser.getValue(e, KEY_HIGHEST));
Log.v(TAG, "indexmap=" + map);
map1.put(KEY_AVERAGE, "Average units = " + parser.getValue(e, KEY_AVERAGE));
Log.v(TAG, "indexmi=" + map1);
map2.put(KEY_LOWEST, "Lowest units = " +parser.getValue(e, KEY_LOWEST));
Log.v(TAG, "indexmi=" + map2);
// adding HashList to ArrayList
menuItems.add(map);
Log.v(TAG, "indexmi=" + menuItems);
menuItems2.add(map1);
Log.v(TAG, "indexmi2=" + menuItems2);
menuItems3.add(map2);
Log.v(TAG, "indexmi3=" + menuItems3);
menuItemsString = menuItems.toString();
menuItemsString2 = menuItems2.toString();
menuItemsString3 = menuItems3.toString();
}
for (int i = 0; i < nl2.getLength(); i++)
{
Log.v(TAG, "indexnl2=" + nl2.getLength());
// creating new HashMap
HashMap<String, String> map3 = new HashMap<String, String>();
HashMap<String, String> map4 = new HashMap<String, String>();
HashMap<String, String> map5 = new HashMap<String, String>();
Element e = (Element) nl2.item(i);
// adding each child node to HashMap key => value
map3.put(KEY_HIGHEST, "Highest units = " + parser.getValue(e, KEY_HIGHEST));
Log.v(TAG, "indexmaps3=" + map3);
map4.put(KEY_AVERAGE, "Average units = " + parser.getValue(e, KEY_AVERAGE));
Log.v(TAG, "indexmaps4=" + map4);
map5.put(KEY_LOWEST, "Lowest units = " +parser.getValue(e, KEY_LOWEST));
Log.v(TAG, "indexmaps5=" + map5);
// adding HashList to ArrayList
menuItems4.add(map3);
Log.v(TAG, "indexmi4=" + menuItems4);
menuItems5.add(map4);
Log.v(TAG, "indexmi5=" + menuItems5);
menuItems6.add(map5);
Log.v(TAG, "indexmi6=" + menuItems6);
menuItemsString4 = menuItems4.toString();
menuItemsString5 = menuItems5.toString();
menuItemsString6 = menuItems6.toString();
}
}
catch (IOException ex)
{
try
{
throw new IOException("Error connecting");
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//String[] combinationString = new String[] { result, result2 };
String[] menuItemsCollection = new String[5];
menuItemsCollection[0] = menuItemsString;
menuItemsCollection[1] = menuItemsString2;
menuItemsCollection[2] = menuItemsString3;
menuItemsCollection[3] = menuItemsString4;
menuItemsCollection[4] = menuItemsString5;
menuItemsCollection[5] = menuItemsString6;
return menuItemsCollection;
}
答案 0 :(得分：0)
初始化中存在拼写错误。您正在初始化menuItems 4两次。
改变这个：
menuItems4 = new ArrayList<HashMap<String, String>>();
menuItems4 = new ArrayList<HashMap<String, String>>();
到此：
menuItems4 = new ArrayList<HashMap<String, String>>();
menuItems5 = new ArrayList<HashMap<String, String>>();