MainActivity.DownloadWebpageTask不是抽象的，不覆盖AsyncTask的抽象方法doInBackground（字符串...） [英] MainActivity.DownloadWebpageTask is not abstract and does not override abstract method doInBackground(String...) in AsyncTask

问题描述

 公共类MainActivity延伸活动{    TextView的电视;    @覆盖
    保护无效的onCreate（捆绑savedInstanceState）{
        super.onCreate（savedInstanceState）;
        的setContentView（R.layout.activity_main）;        电视=（的TextView）findViewById（R.id.data）;        串的serviceUrl = - ; //我不能表现出来
        串的serviceKey = - ; //我不能表现出来
        的serviceKey = URLEn coder.en code（的serviceKey）;
        字符串strSrch =406;
        字符串strUrl =的serviceUrl + + +的serviceKey与＆amp; strSrch =的serviceKey =？+ strSrch;        新DownloadWebpageTask（）执行（strUrl）;
    }    私有类DownloadWebpageTask扩展的AsyncTask＆LT;弦乐，太虚，字符串＆GT; {        @覆盖
        保护字符串doInBackgroud（字符串的URL ...）{
            尝试{
                返回（字符串）downloadUrl（（字符串）网址[0]）;
            }赶上（IOException异常五）{
                返回下载失败;
            }
        }        保护无效onPostExecute（字符串结果）{
            tv.append（结果+\\ n）;
            tv.append（=======解析结果========= \\ n）;            尝试{
                XmlPullParserFactory工厂= XmlPullParserFactory.newInstance（）;
                factory.setNamespaceAware（真）;
                XmlPullParser XPP = factory.newPullParser（）;                xpp.setInput（新StringReader（结果））;
                INT EVENTTYPE = xpp.getEventType（）;
                布尔BSET = FALSE;
                而（EVENTTYPE！= XmlPullParser.END_DOCUMENT）{
                    如果（EVENTTYPE == XmlPullParser.START_DOCUMENT）{
                        ;
                    }否则如果（EVENTTYPE == XmlPullParser.START_TAG）{
                        字符串TAG_NAME = xpp.getName（）;
                        如果（tag_name.equals（busRouteNm）|| tag_name.equals（busRouteId））
                            BSET =真;
                    }否则如果（EVENTTYPE == XmlPullParser.TEXT）{
                        如果（BSET）{
                            字符串内容= xpp.getText（）;
                            tv.append（内容+\\ n）;
                            BSET = FALSE;
                        }
                    }否则如果（EVENTTYPE == XmlPullParser.END_TAG）{
                        ;
                    }
                    EVENTTYPE = xpp.next（）;
                }
            }赶上（例外五）{
                tv.setText（e.getMessage（））;
            }
        }        私人字符串downloadUrl（字符串myurl）抛出IOException            HttpURLConnection的康恩= NULL;
            尝试{
                网址URL =新的URL（myurl）;
                康恩=（HttpURLConnection类）url.openConnection（）;
                BUF的BufferedInputStream =新的BufferedInputStream（conn.getInputStream（））;
                的BufferedReader bufreader =新的BufferedReader（新的InputStreamReader（BUF，UTF-8））;
                串线= NULL;
                字符串页=;
                而（（行= bufreader.readLine（））！= NULL）{
                    网页+ =行;
                }
                返回页面;
            } {最后
                conn.disconnect（）;
            }
        }
    }}
 

私有类DownloadWebpageTask扩展的AsyncTask
此行有错误：

  

错误：（44 13）错误：MainActivity.DownloadWebpageTask不是抽象的，在AsyncTask的不重写抽象方法doInBackground（字符串...）

解决方案

在错字方法名。更改

 保护字符串doInBackgroud
 

到

 保护字符串doInBackground
 

public class MainActivity extends Activity {

    TextView tv;

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

        tv = (TextView) findViewById(R.id.data);

        String serviceUrl = "-"; // I can not show it
        String serviceKey = "-"; // I can not show it
        serviceKey = URLEncoder.encode(serviceKey);
        String strSrch = "406";
        String strUrl = serviceUrl + "?ServiceKey=" + serviceKey + "&strSrch=" + strSrch;

        new DownloadWebpageTask().execute(strUrl);
    }

    private class DownloadWebpageTask extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackgroud(String... urls) {
            try {
                return (String)downloadUrl((String)urls[0]);
            } catch (IOException e) {
                return "Download Fail";
            }
        }

        protected void onPostExecute(String result) {
            tv.append(result + "\n");
            tv.append("=======parsing result=========\n");

            try {
                XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
                factory.setNamespaceAware(true);
                XmlPullParser xpp = factory.newPullParser();

                xpp.setInput(new StringReader(result));
                int eventType = xpp.getEventType();
                boolean bSet = false;
                while (eventType != XmlPullParser.END_DOCUMENT) {
                    if (eventType == XmlPullParser.START_DOCUMENT) {
                        ;
                    } else if (eventType == XmlPullParser.START_TAG) {
                        String tag_name = xpp.getName();
                        if (tag_name.equals("busRouteNm") || tag_name.equals("busRouteId"))
                            bSet = true;
                    } else if (eventType == XmlPullParser.TEXT) {
                        if (bSet) {
                            String content = xpp.getText();
                            tv.append(content + "\n");
                            bSet = false;
                        }
                    } else if (eventType == XmlPullParser.END_TAG) {
                        ;
                    }
                    eventType = xpp.next();
                }
            } catch (Exception e) {
                tv.setText(e.getMessage());
            }
        }

        private String downloadUrl(String myurl) throws IOException {

            HttpURLConnection conn = null;
            try {
                URL url = new URL(myurl);
                conn = (HttpURLConnection) url.openConnection();
                BufferedInputStream buf = new BufferedInputStream(conn.getInputStream());
                BufferedReader bufreader = new BufferedReader(new InputStreamReader(buf, "utf-8"));
                String line = null;
                String page = "";
                while ((line = bufreader.readLine()) != null) {
                    page += line;
                }
                return page;
            } finally {
                conn.disconnect();
            }
        }
    }

}

"private class DownloadWebpageTask extends AsyncTask " This line has error :

Error:(44, 13) error: MainActivity.DownloadWebpageTask is not abstract and does not override abstract method doInBackground(String...) in AsyncTask

解决方案

Typo in method name. Change

protected String doInBackgroud

to

protected String doInBackground

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