XML解析给我一个错误，然后崩溃应用程序

Question

我正在创建一个简单的登录页面，它将响应REST服务提供的响应。响应如果以XML格式返回并通过浏览器检查该服务是否正常工作。

每次我单击“登录”按钮时，应用程序强制关闭，我已经调试了它，但仍然无法弄明白。

startLogin已更改为AsyncTask

在Main活动中，我在我的按钮点击监听器上调用startLogin。

公共类MainActivity扩展了Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    findViewById(R.id.loginButton).setOnClickListener(
            new OnClickListener(){
        public void onClick(View view){
            new startLogin().execute("");
        }
    });
}

以下是我创建的异步任务

private class startLogin extends AsyncTask<String, Void, String> {
        final EditText User= (EditText) findViewById(R.id.usernameEditText);
        final EditText Pass= (EditText) findViewById(R.id.passwordEditText);
        final TextView testLabel = (TextView) findViewById(R.id.testLabel);
          @Override
          protected String doInBackground(String... params) {

            String finished= "have finished the login task.";
            int z = 0;
            String username = User.getText().toString();
            String password = Pass.getText().toString();
            String getOne = "http://demo.relocationmw.com/ws_docmgmt/mobile.asmx/GetLogin?userName=";
            String getTwo = "&passWord=";
            String URL = getOne + username + getTwo + password;  
            String KEY_ITEM = "Response";
            String KEY_SUCCESS = "Success";
            String KEY_FAIL = "Fail";
            String KEY_UID = "UID";
            testLabel.setText("Success to Async");
            String xml = getXMLFromUrl(URL);
            Document doc = getDomElement(xml);

            if(xml != null)
            {
                NodeList nl = doc.getElementsByTagName(KEY_ITEM);
                Element e = (Element) nl.item(z);
                String successString = getValue(e,KEY_SUCCESS);
                String UIDString = getValue(e,KEY_UID);
                String failString = getValue(e,KEY_FAIL);
                String loginError = "Please check username and password.";
                if(failString.equals("Fail")){
                    int duration = Toast.LENGTH_LONG;
                    Toast toast = Toast.makeText(MainActivity.this, loginError, duration);
                    toast.setGravity(Gravity.TOP|Gravity.RIGHT, 0, 0);
                    toast.show();
                }
                else{
                    if(successString.equals("Success")){
                        Intent intent = new Intent (MainActivity.this, HomeActivity.class);
                        startActivity(intent);
                    }
                }
            }else
            {
                Toast toast = Toast.makeText(MainActivity.this, "No Connection to Retrieve Data.", Toast.LENGTH_LONG);
                toast.show();
            }
            return finished;
          }      

          @Override
          protected void onPostExecute(String result) {
          }

          @Override
          protected void onPreExecute() {
          }

          @Override
          protected void onProgressUpdate(Void... values) {
          }

    //XML Parsing Start
        public String getXMLFromUrl(String url){
            String xml = null;
            try{
                DefaultHttpClient client = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);

                HttpResponse httpResponse = client.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                xml = EntityUtils.toString(httpEntity);
            }catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            } catch (ClientProtocolException e) {
                // Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // Auto-generated catch block
                e.printStackTrace();
            }
            return xml;
        }

        public Document getDomElement(String xml){
            Document doc = null;
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            try {

                DocumentBuilder db = dbf.newDocumentBuilder();

                InputSource is = new InputSource();
                    is.setCharacterStream(new StringReader(xml));
                    doc = db.parse(is); 

                } catch (ParserConfigurationException e) {
                    Log.e("Error: ", e.getMessage());
                    return null;
                } catch (SAXException e) {
                    Log.e("Error: ", e.getMessage());
                    return null;
                } catch (IOException e) {
                    Log.e("Error: ", e.getMessage());
                    return null;
                }
                    // return DOM
                return doc;
        }

        public String getValue(Element item, String str) {
            NodeList n = ((Document) item).getElementsByTagName(str);
            return getElementValue(n.item(0));
        }

        public final String getElementValue( Node elem ) {
                 Node child;
                 if( elem != null){
                     if (elem.hasChildNodes()){
                         for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){
                             if( child.getNodeType() == Node.TEXT_NODE  ){
                                 return child.getNodeValue();
                             }
                         }
                     }
                 }
                 return "";
          }
    //XML Parsing Stop

    }
 }

XML“MainActivity”：

<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:background="@color/BackgroundGrey"
    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=".MainActivity" >

    <Button
        android:id="@+id/loginButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="90dp"
        android:text="@string/loginbuttonlabel" />

    <EditText
        android:id="@+id/passwordEditText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/loginButton"
        android:layout_centerHorizontal="true"
        android:layout_margin="5dp"
        android:background="@color/White"
        android:ems="10"
        android:inputType="text|textPassword" />

    <EditText
        android:id="@+id/usernameEditText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/passwordEditText"
        android:layout_centerHorizontal="true"
        android:layout_margin="5dp"
        android:background="@color/White"
        android:ems="10"
        android:inputType="text|textPassword" >

        <requestFocus />
    </EditText>

    <TextView
        android:id="@+id/testLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/loginButton"
        android:layout_alignParentTop="true"
        android:layout_marginTop="93dp"
        android:text="TextView" />

</RelativeLayout>

LogCat错误：

02-20 02:56:39.927: E/AndroidRuntime(1018): FATAL EXCEPTION: AsyncTask #1
02-20 02:56:39.927: E/AndroidRuntime(1018): java.lang.RuntimeException: An error occured while executing doInBackground()
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.os.AsyncTask$3.done(AsyncTask.java:299)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at java.util.concurrent.FutureTask.run(FutureTask.java:239)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at java.lang.Thread.run(Thread.java:856)
02-20 02:56:39.927: E/AndroidRuntime(1018): Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4746)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:823)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.view.View.requestLayout(View.java:15468)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.view.View.requestLayout(View.java:15468)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.view.View.requestLayout(View.java:15468)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.view.View.requestLayout(View.java:15468)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:318)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.view.View.requestLayout(View.java:15468)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.widget.TextView.checkForRelayout(TextView.java:6313)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.widget.TextView.setText(TextView.java:3567)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.widget.TextView.setText(TextView.java:3425)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.widget.TextView.setText(TextView.java:3400)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at com.testingapp.MainActivity$startLogin.doInBackground(MainActivity.java:83)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at com.testingapp.MainActivity$startLogin.doInBackground(MainActivity.java:1)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
02-20 02:56:39.927: E/AndroidRuntime(1018):     at java.util.concurrent.FutureTask.run(FutureTask.java:234)
02-20 02:56:39.927: E/AndroidRuntime(1018):     ... 3 more

我现在能够将问题缩小到异步活动。 非常感谢任何帮助！

Answer 1

让你的getXMLFromUrl（）方法放在一个新线程中（例如：AsyncTask）。

Answer 2

我没有读过您的代码，但堆栈跟踪包含No address associated with hostname - 我从那里开始。

尝试将构建的URL放入浏览器，wget或您喜欢的任何内容，并查看请求实际返回的内容。当您可以看到预期的结果时，请将其编入您的代码中。另外，请确保您的代码提出相同的请求。

Answer 3

类TestAsyncTask扩展了AsyncTask {

    @Override
    protected String doInBackground(String... params) {
        return getXMLFromUrl(params[0]);
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        ....
    }
}

Answer 4

私有类startLogin扩展了AsyncTask {

 @Override
protected String doInBackground(String... params) {
    return getXMLFromUrl(params[0]);
}

@Override protected void onPostExecute(String result) {
     if(result != null) {
     String xml = result;
     Document doc = getDomElement(xml);
            NodeList nl = doc.getElementsByTagName(KEY_ITEM);
            Element e = (Element) nl.item(z);
            String successString = getValue(e,KEY_SUCCESS);
            String UIDString = getValue(e,KEY_UID);
            String failString = getValue(e,KEY_FAIL);
            String loginError = "Please check username and password.";
            if(failString.equals("Fail")){
                int duration = Toast.LENGTH_LONG;
                Toast toast = Toast.makeText(MainActivity.this, loginError, duration);
                toast.setGravity(Gravity.TOP|Gravity.RIGHT, 0, 0);
                toast.show();
            }
            else{
                if(successString.equals("Success")){
                    Intent intent = new Intent (MainActivity.this, HomeActivity.class);
                    startActivity(intent);
                }
            }
        }else
        {
            Toast toast = Toast.makeText(MainActivity.this, "No Connection to Retrieve Data.", Toast.LENGTH_LONG);
            toast.show();
        }

}

}

//调用asynctask new startlogin（）。execute（URL）;