在主线程上没有网络调用，但是我仍然遇到相同的错误: NetworkOnMainThreadException 。
MainActivity.class:
public class MainActivity extends Activity
{
private TextView tv1,
tv2,
tv3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv1 = (TextView) findViewById(R.id.tv1);
tv2 = (TextView) findViewById(R.id.tv2);
tv3 = (TextView) findViewById(R.id.tv3);
String xmlUrl = "https://dl.dropboxusercontent.com/s/wbuxa7cutb6/update.xml";
new DownloadData().execute(xmlUrl);
}
public class DownloadData extends AsyncTask<String, Void, InputStream>
{
@Override
protected InputStream doInBackground(String... urls) {
try {
URL url = new URL(urls[0]);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setReadTimeout(10000);
connection.setConnectTimeout(15000);
connection.setRequestMethod("GET");
connection.setDoInput(true);
connection.connect();
int response = connection.getResponseCode();
Log.d("", "The response is: " + response);
return connection.getInputStream();
//return new Scanner(connection.getInputStream(),"UTF-8").useDelimiter("\\A").next();
}
catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(InputStream is)
{
List<List<String>> lists = new XmlParser().parse(is);
tv1.setText(lists.get(0).get(0));
tv2.setText(lists.get(0).get(1));
tv3.setText(lists.get(0).get(2));
}
}
}
您怎么看，仅在 doInBackground()中才需要互联网，但错误仍然存在。
日志:
01-13 03:18:37.668: E/AndroidRuntime(5679): FATAL EXCEPTION: main
01-13 03:18:37.668: E/AndroidRuntime(5679): android.os.NetworkOnMainThreadException
01-13 03:18:37.668: E/AndroidRuntime(5679): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
01-13 03:18:37.668: E/AndroidRuntime(5679): at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl$SSLInputStream.read(OpenSSLSocketImpl.java:657)
01-13 03:18:37.668: E/AndroidRuntime(5679): at libcore.net.http.FixedLengthInputStream.read(FixedLengthInputStream.java:45)
01-13 03:18:37.668: E/AndroidRuntime(5679): at libcore.io.Streams.readSingleByte(Streams.java:41)
01-13 03:18:37.668: E/AndroidRuntime(5679): at libcore.net.http.AbstractHttpInputStream.read(AbstractHttpInputStream.java:63)
01-13 03:18:37.668: E/AndroidRuntime(5679): at org.kxml2.io.KXmlParser.setInput(KXmlParser.java:1623)
01-13 03:18:37.668: E/AndroidRuntime(5679): at org.apache.harmony.xml.parsers.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:111)
01-13 03:18:37.668: E/AndroidRuntime(5679): at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:132)
01-13 03:18:37.668: E/AndroidRuntime(5679): at neviat.test.downloaddata.XmlParser.parse(XmlParser.java:39)
01-13 03:18:37.668: E/AndroidRuntime(5679): at neviat.test.downloaddata.MainActivity$DownloadData.onPostExecute(MainActivity.java:70)
01-13 03:18:37.668: E/AndroidRuntime(5679): at neviat.test.downloaddata.MainActivity$DownloadData.onPostExecute(MainActivity.java:1)
01-13 03:18:37.668: E/AndroidRuntime(5679): at android.os.AsyncTask.finish(AsyncTask.java:631)
01-13 03:18:37.668: E/AndroidRuntime(5679): at android.os.AsyncTask.access$600(AsyncTask.java:177)
01-13 03:18:37.668: E/AndroidRuntime(5679): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
01-13 03:18:37.668: E/AndroidRuntime(5679): at android.os.Handler.dispatchMessage(Handler.java:99)
01-13 03:18:37.668: E/AndroidRuntime(5679): at android.os.Looper.loop(Looper.java:137)
01-13 03:18:37.668: E/AndroidRuntime(5679): at android.app.ActivityThread.main(ActivityThread.java:5041)
01-13 03:18:37.668: E/AndroidRuntime(5679): at java.lang.reflect.Method.invokeNative(Native Method)
01-13 03:18:37.668: E/AndroidRuntime(5679): at java.lang.reflect.Method.invoke(Method.java:511)
01-13 03:18:37.668: E/AndroidRuntime(5679): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-13 03:18:37.668: E/AndroidRuntime(5679): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-13 03:18:37.668: E/AndroidRuntime(5679): at dalvik.system.NativeStart.main(Native Method)
XmlParser:
public class XmlParser
{
private DocumentBuilderFactory factory;
private DocumentBuilder builder;
private String getNodeValue(NamedNodeMap map, String key) {
String nodeValue = null;
Node node = map.getNamedItem(key);
if (node != null)
nodeValue = node.getNodeValue();
return nodeValue;
}
public List<List<String>> parse(InputStream inStream)
{
List<List<String>> lists = new ArrayList<List<String>>();
try {
factory = DocumentBuilderFactory.newInstance();
builder = factory.newDocumentBuilder();
builder.isValidating();
Document doc = builder.parse(inStream, null);
doc.getDocumentElement().normalize();
NodeList itemList = doc.getElementsByTagName("item");
final int length = itemList.getLength();
for (int i = 0; i < length; i++) {
final NamedNodeMap attr = itemList.item(i).getAttributes();
final String dataId = getNodeValue(attr, "id");
final String dataName = getNodeValue(attr, "name");
final String dataUrl = getNodeValue(attr, "url");
List<String> list = new ArrayList<String>();
list.add(dataId);
list.add(dataName);
list.add(dataUrl);
lists.add(list);
}
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ParserConfigurationException e) {
e.printStackTrace();
}
return lists;
}
}
最佳答案
您将InputStream返回到主线程，这意味着您将在onPostExecute方法(在主线程上运行)中进行网络操作。您必须在后台线程中获取所有数据。仅当数据不是来自网络时，才可以从InputStream解析UI线程上的数据，这不是您的情况。
简而言之，请将您的List<List<String>> lists = new XmlParser().parse(is);代码放入doInBackground方法中，然后返回您的列表。
澄清:您所缺少的是流媒体的用途。它们是要使用的，因此您无需一次加载所有数据(从而降低了资源使用率，尤其是内存消耗)。当您将InputStream传递给UI线程时，您不知道已经下载了多少数据(如果有的话)。想象一下，例如，您正在下载一个巨大的XML文件(30MB)，并且需要对其进行解析。使用InputStream避免了下载整个程序，将其放入内存(这会使应用程序崩溃)和解析的麻烦。使用Streams，该方法将下载一点数据，进行解析并释放已用的内存，因此内存消耗始终保持较低水平。