用于调用JSOUP以分析不起作用的表的异步任务

我是android的新手，这是我第一次使用JSoup和Async任务。我想在我的应用程序中从这个网站（aviationweather.gov）获得航空天气预报。

我试图用Jsoup解析的表数据如下：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<HTML>
<HEAD>
<TITLE>ADDS - TAFS form results</TITLE>
<LINK REL="StyleSheet" type="text/css" HREF="/layout/awc/mystyle.css">
</HEAD>
<BODY BGCOLOR="#FFFFFF">
  <TABLE SUMMARY="This table is used for formatting purposes only" BORDER=0 CELLPADDING=3 CELLSPACING=0>
    <TR VALIGN="top">
      <TD ALIGN="left" COLSPAN="2">
        <H2>Aviation Digital Data Service (ADDS)</H2>
        Output produced by TAFs form (1417&#160;UTC&nbsp;22 November 2013)<BR>
        found at <A HREF="http://www.aviationweather.gov/adds/tafs/"> http://www.aviationweather.gov/adds/tafs/</A><BR>&#160;<BR>
      </TD>
    </TR>
    <TR VALIGN="top">
      <TD ALIGN="left" COLSPAN="2">
        <PRE><font face="Monospace,Courier" size="+1">TAF EGXC 221321Z 2215/2224 01010KT 9999 SCT035 
     PROB30 
     TEMPO 2216/2224 BKN020
       </font></PRE>
        <PRE><font face="Monospace,Courier" size="+1">TAF EGOV 221323Z 2215/2218 01008KT 9999 FEW020
       </font></PRE>
        <PRE><font face="Monospace,Courier" size="+1">TAF EGXE 221047Z 2212/2217 34008KT 9999 FEW020 SCT030 
     TEMPO 2212/2215 -SHRA SCT018
       </font></PRE>
      </TD>
    </TR>
  </TABLE>
</BODY>
</HTML>

表格的行数与用户要求的机场数量有关。

当以下代码点击图像按钮时，我正在调用异步任务：

new getPage().execute();

getPage（）看起来像这样：

private class getPage extends AsyncTask<String, Void, String> {
    ProgressDialog prog;
    protected void onPreExecute() {
        prog = new ProgressDialog(Weathergrabber.this);
        prog.setMessage("Loading....");
        prog.show();
    }
    @Override
    protected String doInBackground(String... params) {
        try {
            // lets format the icaos the user is interested in
            if (etICAO1.getText().toString().length() > 0) {
                icaos = etICAO1.getText().toString();
            }
            if (etICAO1.getText().toString().length() == 0) {
                // editText is empty
            }
            if (etICAO2.getText().toString().length() > 0) {
                icaos = icaos + "+" + etICAO2.getText().toString();
            }
            if (etICAO2.getText().toString().length() == 0) {
                // editText is empty
            }
            if (etICAO3.getText().toString().length() > 0) {
                icaos = icaos + "+" + etICAO3.getText().toString();
            }
            if (etICAO3.getText().toString().length() == 0) {
                // editText is empty
            }
            if (etICAO4.getText().toString().length() > 0) {
                icaos = icaos + "+" + etICAO4.getText().toString();
            }
            if (etICAO4.getText().toString().length() == 0) {
                // editText is empty
            }
            if (etICAO5.getText().toString().length() > 0) {
                icaos = icaos + "+" + etICAO5.getText().toString();
            }
            if (etICAO5.getText().toString().length() == 0) {
                // editText is empty
            }
            if (etICAO6.getText().toString().length() > 0) {
                icaos = icaos + "+" + etICAO6.getText().toString();
            }
            if (etICAO6.getText().toString().length() == 0) {
                // editText is empty
            }
            if (etICAO7.getText().toString().length() > 0) {
                icaos = icaos + "+" + etICAO7.getText().toString();
            }
            if (etICAO7.getText().toString().length() == 0) {
                // editText is empty
            }
            if (etICAO8.getText().toString().length() > 0) {
                icaos = icaos + "+" + etICAO8.getText().toString();
            }
            if (etICAO8.getText().toString().length() == 0) {
                // editText is empty
            }
            // now lets format the webaddress
            finalWebAddress = websitePart1 + icaos + websitePart2;
            // try to get the data
            Toast.makeText(getApplicationContext(),
                    "Collecting data from " + finalWebAddress,
                    Toast.LENGTH_LONG).show();
            Document doc;
            doc = Jsoup.connect(finalWebAddress).userAgent("Mozilla").get();
            Element tableElement = doc.select("tr").first();
            theWeather = doc.title();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return theWeather;
    }
    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        prog.dismiss();
        tvWeather.setText(result);
    }
}

我希望textview tvWeather能将表数据添加到其中，但应用程序正在崩溃，logcat为：

11-22 14:46:43.100: E/AndroidRuntime(2507): FATAL EXCEPTION: AsyncTask #1
11-22 14:46:43.100: E/AndroidRuntime(2507): java.lang.RuntimeException: An error occured while executing doInBackground()
11-22 14:46:43.100: E/AndroidRuntime(2507):     at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.lang.Thread.run(Thread.java:856)
11-22 14:46:43.100: E/AndroidRuntime(2507): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
11-22 14:46:43.100: E/AndroidRuntime(2507):     at android.os.Handler.<init>(Handler.java:121)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at android.widget.Toast$TN.<init>(Toast.java:361)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at android.widget.Toast.<init>(Toast.java:97)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at android.widget.Toast.makeText(Toast.java:254)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at com.Weathergrabber$getPage.doInBackground(Weathergrabber.java:293)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at com.Weathergrabber$getPage.doInBackground(Weathergrabber.java:1)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
11-22 14:46:43.100: E/AndroidRuntime(2507):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)

正如我所说的，我是使用AsyncTask和Jsoup的新手，所以不确定错误在哪里。希望我已经提供了足够的细节来帮助生成答案。

谢谢；

Andy

我看到你的问题了。您正试图在后台线程中制作Toast。你只能在ui线程中制作Toast。

试试类似的东西：

new Handler().post(new Runnable() {
    @Override
    public void run() {
        // Code here will run in UI thread
    }
});

或者，您也可以使用AsyncTask的publishProgress和onProgressUpdate方法从AsyncTask调用toast作为进度消息。onProgressUpdate

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